1
00:00:00,036 --> 00:00:03,485
Hi, welcome back to the Neil Ashton
podcast.

2
00:00:03,486 --> 00:00:08,658
Combustion is one of those areas of CFD
and fluid mechanics where

3
00:00:08,659 --> 00:00:12,538
everything gets harder once. Turbulence,
thermodynamics, hundreds of chemical

4
00:00:12,539 --> 00:00:17,280
species, vastly different time scales, and
heat releasing and all interacting.

5
00:00:17,281 --> 00:00:22,453
My guest today is somebody who has spent
his whole career trying

6
00:00:22,454 --> 00:00:26,333
to make those problems computable, trying
to solve them.

7
00:00:26,334 --> 00:00:29,351
Daniel Mira Martínez is head of the

8
00:00:29,352 --> 00:00:33,853
propulsion technologies group at the
Barcelona Supercomputing Center.

9
00:00:33,854 --> 00:00:38,233
It's a wide-ranging conversation, I think,
about physics, computing, and the

10
00:00:38,234 --> 00:00:41,816
future of propulsion. And I hope you enjoy
it.

11
00:00:41,817 --> 00:00:49,317
what makes combustion so hard compared to
let's say incompressible flow over

12
00:00:51,218 --> 00:00:52,785
a car?

13
00:00:52,786 --> 00:01:00,286
Well, I don't know. Perhaps the first
answer is thermodynamics.

14
00:01:02,874 --> 00:01:10,374
think one of the aspects that make the...

15
00:01:11,057 --> 00:01:15,964
this application field a little bit more
complex than conventional

16
00:01:15,965 --> 00:01:21,853
aerodynamics or conventional flows is the
fact that you have to satisfy

17
00:01:21,854 --> 00:01:25,779
the thermodynamics. And the thermodynamics
involving multi-component flows,

18
00:01:25,780 --> 00:01:28,723
gases that have a different composition.

19
00:01:28,724 --> 00:01:34,121
And then because they have different
composition, they have different partial

20
00:01:34,122 --> 00:01:40,010
pressures. And therefore, when you want to
describe the evolution of the

21
00:01:40,011 --> 00:01:40,991
flow having

22
00:01:41,224 --> 00:01:47,168
these different compositions then the
equations and the closers that you need

23
00:01:47,169 --> 00:01:53,111
to provide increase and then if you add
also the fact that

24
00:01:53,112 --> 00:01:58,064
you can have combustion that you have a
heat release.

25
00:01:58,065 --> 00:02:04,008
Heat release always occurs in a very very
thin layer then you

26
00:02:04,009 --> 00:02:08,961
start having interaction with this heat
release with the flow

27
00:02:09,169 --> 00:02:14,011
this couple system combined with the
thermodynamics again, with the enthalpy

28
00:02:14,012 --> 00:02:19,294
variation, with the properties that
change, then this is why it makes,

29
00:02:19,295 --> 00:02:24,576
for example, I don't know, multiphase
flows for combustion a little bit

30
00:02:24,577 --> 00:02:29,859
more complex or compressible flows for
combustion a little bit more complex

31
00:02:29,860 --> 00:02:33,380
or supercritical fluids for combustion
also more complex.

32
00:02:33,381 --> 00:02:38,663
So when you add the kind of problems that
you have always

33
00:02:38,664 --> 00:02:39,164
in

34
00:02:39,324 --> 00:02:43,971
in CFD and then you add a multi-component
reacting flows everything becomes

35
00:02:43,972 --> 00:02:47,069
a little bit more messy at the end.

36
00:02:47,070 --> 00:02:54,100
And your main focus has been more on the
jet engine side,

37
00:02:54,101 --> 00:02:58,201
right? Would that be fair to say?

38
00:02:58,202 --> 00:03:04,281
Yes, yes exactly. from my PhD it's quite
funny at this point

39
00:03:04,282 --> 00:03:10,362
because when I started the PhD I did my
PhD in hydrogen

40
00:03:10,363 --> 00:03:16,442
combustion. I started in 2009 and then I
found it very interesting

41
00:03:16,443 --> 00:03:18,469
as turbine hydrogen enriched.

42
00:03:18,470 --> 00:03:23,766
flows or fuels for gas turbine
applications and then I enjoyed very

43
00:03:23,767 --> 00:03:29,063
much. There were of course quite a lot of
activities related to

44
00:03:29,064 --> 00:03:34,360
hydrogen but it was from my understanding
more related to that hydrogen

45
00:03:34,361 --> 00:03:39,656
is a small, I mean it's a fuel that the
chemistry is

46
00:03:39,657 --> 00:03:44,953
well characterized, it's small so people
prefer to look at hydrogen because

47
00:03:44,954 --> 00:03:48,043
they don't have as many species as

48
00:03:48,453 --> 00:03:51,344
hydrocarbon, for example methane or
propane.

49
00:03:51,345 --> 00:03:57,125
But then it was quite interesting and it
was of course quite...

50
00:03:57,126 --> 00:04:02,678
well explained in the literature back then
that hydrogen was quite special

51
00:04:02,679 --> 00:04:08,232
because it had some particular properties
that make the combustion of hydrogen

52
00:04:08,233 --> 00:04:13,785
quite different from hydrocarbon fuels.
But then after I started the PhD,

53
00:04:13,786 --> 00:04:18,876
I talked to my supervisor and I said, I
like hydrogen.

54
00:04:18,877 --> 00:04:20,264
So I said,

55
00:04:20,265 --> 00:04:25,397
Just hydrogen is not a fuel, it's more
like a vector, energy

56
00:04:25,398 --> 00:04:30,530
vector. So maybe you can try to find
something else if you

57
00:04:30,531 --> 00:04:34,380
still like combustion. And then that was
what happened.

58
00:04:34,381 --> 00:04:39,513
And then after that, after some years,
hydrogen started to take a

59
00:04:39,514 --> 00:04:42,935
lot of momentum and a lot of interest.

60
00:04:42,936 --> 00:04:48,068
And now hydrogen is really at the heart of
the new generation

61
00:04:48,069 --> 00:04:50,207
of sustainable fuels or electricity.

62
00:04:50,368 --> 00:04:54,181
based fuels so

63
00:04:54,182 --> 00:04:59,685
So yeah, and since then, my main
background has been aerospace, fuel

64
00:04:59,686 --> 00:05:04,272
combustors, gas turbine combustors. But
more recently, with my current

65
00:05:04,273 --> 00:05:09,776
position, we try to model also other
applications related to combustion, like

66
00:05:09,777 --> 00:05:15,280
furnaces, for example. And this has been a
new topic for me

67
00:05:15,281 --> 00:05:20,785
over the last three, four years that I was
trying to understand

68
00:05:20,786 --> 00:05:24,454
and was trying to deal with these
configurations.

69
00:05:24,455 --> 00:05:31,736
And so maybe before we get to the CFD
modeling challenges, what's

70
00:05:31,737 --> 00:05:37,804
the main changes and benefits and
challenges between hydrocarbon combustion

71
00:05:37,805 --> 00:05:44,479
and hydrogen combustion? Why is the
aerospace industry so interested in

72
00:05:44,480 --> 00:05:45,693
hydrogen combustion?

73
00:05:45,694 --> 00:05:50,742
Well, I would say there is one main
reason.

74
00:05:50,743 --> 00:05:57,474
Well, there is one and it's actually
related to a few others,

75
00:05:57,475 --> 00:06:01,402
which is the carbonization and energy
dependency.

76
00:06:01,403 --> 00:06:08,134
So in general, the best fuel is the most
energetic fuel, the

77
00:06:08,135 --> 00:06:14,866
one, but you can measure the energetic
fuels in terms of energy.

78
00:06:14,867 --> 00:06:19,149
per kilogram or energy per volume per
liter.

79
00:06:19,150 --> 00:06:25,574
So depending on your application, you
might be interested in having fuels

80
00:06:25,575 --> 00:06:31,999
that have a lot of energy, kilojoules per
kilogram or kilojoules per

81
00:06:32,000 --> 00:06:33,070
liter. So.

82
00:06:33,071 --> 00:06:39,029
Liquid fuels are dominant in the industry
because they have lot of

83
00:06:39,030 --> 00:06:44,988
high density. So in a liter, then you can
have lot of

84
00:06:44,989 --> 00:06:49,457
kilograms of fuel. Hydrogen is not the
case to...

85
00:06:49,458 --> 00:06:55,177
per volume is not that interesting. You
need big volumes at room

86
00:06:55,178 --> 00:07:00,897
temperature or room conditions to have a
lot of mass of fuel.

87
00:07:00,898 --> 00:07:06,617
So one of the major problems of the
utilization of hydrogen is

88
00:07:06,618 --> 00:07:11,861
how you are going to bring the hydrogen in
the application.

89
00:07:11,862 --> 00:07:17,581
If it's a stationary application, then
perhaps it's easier because you can

90
00:07:17,582 --> 00:07:19,011
build a pressurized

91
00:07:19,231 --> 00:07:23,270
cryogenic storage and then you can store
the hydrogen there.

92
00:07:23,271 --> 00:07:28,117
are some problems, embrittlement and these
kind of things that can happen

93
00:07:28,118 --> 00:07:32,964
there. Safety also because it's a very
high pressure and low temperature.

94
00:07:32,965 --> 00:07:37,811
But if you have a mobility application
like an airplane or a

95
00:07:37,812 --> 00:07:42,658
car, then things get a little bit more
complicated from the vehicle

96
00:07:42,659 --> 00:07:47,505
point of view. So you need to accommodate
the storage into the

97
00:07:47,506 --> 00:07:49,121
system and then you

98
00:07:49,201 --> 00:07:53,379
end up having to reshape the vehicle
eventually.

99
00:07:53,380 --> 00:07:58,601
But hydrogen is also quite interesting
from the combustion characteristics

100
00:07:58,602 --> 00:08:04,868
point of view because it's very reactive
and then it burns very

101
00:08:04,869 --> 00:08:11,135
fast. If it burns fast it means that you
can produce a

102
00:08:11,136 --> 00:08:13,746
lot of heat very fast.

103
00:08:13,747 --> 00:08:18,897
compared to hydrocarbon. So you can have a
system that can be

104
00:08:18,898 --> 00:08:24,047
also smaller because it burns faster. So
from the operational point of

105
00:08:24,048 --> 00:08:28,769
view, there are differences that can have
certain advantages or certain

106
00:08:28,770 --> 00:08:33,919
disadvantages. The major disadvantage of
hydrogen is that very likely that you

107
00:08:33,920 --> 00:08:36,924
will have to reshape the combustion
system.

108
00:08:36,925 --> 00:08:43,656
to accommodate the injection and also to
accommodate the flame or the

109
00:08:43,657 --> 00:08:48,705
combustion system to operate in the way
you want.

110
00:08:48,706 --> 00:08:49,827
And perhaps...

111
00:08:49,828 --> 00:08:55,142
especially in Europe but also in other
countries, in Asia as well

112
00:08:55,143 --> 00:09:00,456
and in the United States there are at this
point a little

113
00:09:00,457 --> 00:09:05,771
bit less interested in these particular
fuels or applications but because they

114
00:09:05,772 --> 00:09:07,985
have a lot of oil.

115
00:09:07,986 --> 00:09:15,486
then if you are able to burn hydrogen,
hydrogen can be easily

116
00:09:15,868 --> 00:09:22,437
produced locally, for example, from
renewable electricity and an electrolyser,

117
00:09:22,438 --> 00:09:25,065
can produce hydrogen free.

118
00:09:25,066 --> 00:09:31,129
after of course a lot of investment, lot
of infrastructure, but at

119
00:09:31,130 --> 00:09:37,193
the end you become let's say independent
from the generation of the

120
00:09:37,194 --> 00:09:43,257
fuel or the energy system and then you do
not participate in

121
00:09:43,258 --> 00:09:48,310
these geopolitical situations about
availability of fuels, that combustion is

122
00:09:48,311 --> 00:09:54,374
very integrated in the society, so we use
combustion for many applications,

123
00:09:54,375 --> 00:09:54,879
mobility,

124
00:09:54,949 --> 00:10:02,110
heating, domestic use also. So if you are
able somehow to avoid

125
00:10:02,111 --> 00:10:09,270
the dependency of variations in the market
prices and everything, then you

126
00:10:09,271 --> 00:10:12,254
are in a good position.

127
00:10:12,255 --> 00:10:16,973
And how far, you know, before we get into
more of the

128
00:10:16,974 --> 00:10:21,691
modeling challenges, where would you track
from when you did your PhD

129
00:10:21,692 --> 00:10:26,410
in 2009 to now, how is this hydrogen
combustion going from an

130
00:10:26,411 --> 00:10:31,128
industrial adoption? You know, are we 20
years away from it being

131
00:10:31,129 --> 00:10:34,274
something feasible? Is it 10? Is it five?

132
00:10:34,275 --> 00:10:38,206
You know, is there a sense of where that
is?

133
00:10:38,207 --> 00:10:43,905
Okay, no, in fact, it is... I mean, I was
gonna say

134
00:10:43,906 --> 00:10:49,128
surprisingly, but it's not surprising
because at the end, the technological

135
00:10:49,129 --> 00:10:49,604
evolution...

136
00:10:49,604 --> 00:10:54,726
at the end is mainly taken, I would say,
by the companies

137
00:10:54,727 --> 00:10:59,849
and by the demands of the society and also
by the companies

138
00:10:59,850 --> 00:11:04,972
that, you know, they can make profit
providing the technology that the

139
00:11:04,973 --> 00:11:10,095
society actually needs. And this is in
fact what happened with hydrogen.

140
00:11:10,096 --> 00:11:15,218
Of course, there are some political
investment and the European Commission has

141
00:11:15,219 --> 00:11:19,487
a vision for the future associated to
cover partially or

142
00:11:19,667 --> 00:11:25,048
the use of conventional hydrocarbon fuels
by not by only hydrogen because

143
00:11:25,049 --> 00:11:29,980
ammonia is also a quite interesting fuel
nowadays especially for some

144
00:11:29,981 --> 00:11:34,463
applications that I can go a little bit in
detail.

145
00:11:34,464 --> 00:11:36,257
So yeah this question

146
00:11:36,429 --> 00:11:41,214
requires a very long answer so I will try
to be a

147
00:11:41,215 --> 00:11:45,998
bit sure here but you can see if we go
sector by

148
00:11:45,999 --> 00:11:50,783
sector you can actually see that in the
gas turbine sector that

149
00:11:50,784 --> 00:11:55,568
their main priority is a stationary system
and it can be located

150
00:11:55,569 --> 00:12:00,352
in the Middle East, in Asia, in Europe or
the United States

151
00:12:00,353 --> 00:12:05,137
and so the priority is flexibility of fuel
so if you are

152
00:12:05,138 --> 00:12:06,333
in a place

153
00:12:06,334 --> 00:12:10,625
that you can produce, I don't know, you
have...

154
00:12:10,705 --> 00:12:16,692
biogas or you have, I don't know, methane
or propane or you

155
00:12:16,693 --> 00:12:22,679
can produce a lot of hydrocarbon. What you
would like is to

156
00:12:22,680 --> 00:12:28,665
be able to burn this and to not bring
hydrogen by ships

157
00:12:28,666 --> 00:12:34,652
or anything. And in this flexibility of
operation, the industry is moving

158
00:12:34,653 --> 00:12:40,140
quite strong towards the accommodation of
these synthetic fuels, ammonia and

159
00:12:40,141 --> 00:12:40,641
hydrogen.

160
00:12:40,652 --> 00:12:43,709
the I would say

161
00:12:43,710 --> 00:12:49,023
not refer to brands, I would say 30 %
hydrogen in the

162
00:12:49,024 --> 00:12:53,009
fuel has been easily accommodated by all
the manufacturers.

163
00:12:53,010 --> 00:12:58,323
There is a small trick here because 30 %
by volume in

164
00:12:58,324 --> 00:13:03,637
hydrogen is almost nothing in kilograms,
but then there has been demonstration

165
00:13:03,638 --> 00:13:08,952
plants, very few already, over the last
years in which they can

166
00:13:08,953 --> 00:13:13,823
operate with 50%, 60%, 70 % in volume that
make now

167
00:13:13,824 --> 00:13:18,364
a big contribution and also 100 % hydrogen
in a real system.

168
00:13:18,365 --> 00:13:22,904
The problem nowadays is that my technology
can burn hydrogen, but where

169
00:13:22,905 --> 00:13:27,445
do I get the hydrogen? You just give me
the hydrogen and

170
00:13:27,446 --> 00:13:31,986
then I can more or less burn it. In the
aviation sector,

171
00:13:31,987 --> 00:13:35,391
there was a, it's a little bit more
peculiar.

172
00:13:35,392 --> 00:13:39,932
If you allow me to go sector by sector
quickly, I can

173
00:13:39,933 --> 00:13:40,311
do

174
00:13:40,311 --> 00:13:41,281
it and...

175
00:13:41,469 --> 00:13:46,604
And then I can give you more or less what
is my

176
00:13:46,605 --> 00:13:51,739
perspective. It could be a little bit off
in some areas that

177
00:13:51,740 --> 00:13:56,874
I work a bit less, but more or less the
ideas are

178
00:13:56,875 --> 00:14:02,009
more or less this. These are mainly the
discussions that we're having

179
00:14:02,010 --> 00:14:05,004
nowadays in the community are about this.

180
00:14:05,005 --> 00:14:10,139
So for the aviation sector, there was a
huge effort by the

181
00:14:10,140 --> 00:14:11,423
manufacturers to accommodate

182
00:14:11,513 --> 00:14:16,223
hydrogen. There was quite a lot of push
from the political sector

183
00:14:16,224 --> 00:14:18,971
for the carbonization of the aviation
sector.

184
00:14:18,972 --> 00:14:23,681
And then the manufacturers were saying,
hey, we are only representing 4

185
00:14:23,682 --> 00:14:27,213
% of the CO2 emissions worldwide. Why are
we?

186
00:14:27,214 --> 00:14:31,923
Why do we have to invest so much money on
changing everything?

187
00:14:31,924 --> 00:14:36,633
But this is a very, I mean, you know this
well, you

188
00:14:36,634 --> 00:14:40,166
have worked in it also in the aerospace
sector.

189
00:14:40,167 --> 00:14:41,343
It's highly technological.

190
00:14:41,344 --> 00:14:41,717
So

191
00:14:41,717 --> 00:14:48,149
they like challenges and they have
invested and they have pushed a

192
00:14:48,150 --> 00:14:51,901
lot to develop technologies for hydrogen
combustion.

193
00:14:51,902 --> 00:14:58,334
And then there has been quite a few
demonstrators like with some

194
00:14:58,335 --> 00:15:02,622
airlines that they have already done some
flights.

195
00:15:02,623 --> 00:15:08,519
I'm talking about commercial aviation,
civil aviation flying from one country

196
00:15:08,520 --> 00:15:11,199
to another. And that is

197
00:15:11,200 --> 00:15:17,650
really happening in most of the aero
engine manufacturers nowadays they have

198
00:15:17,651 --> 00:15:22,489
technology for hydrogen combustion at
quite a mature stage.

199
00:15:22,490 --> 00:15:28,940
For commercialization it is unclear but
for demonstration stage I think they

200
00:15:28,941 --> 00:15:35,391
all are pretty advanced. The problem is
that for aviation you have

201
00:15:35,392 --> 00:15:41,305
short range, mid range and long range so
for short range

202
00:15:41,306 --> 00:15:44,663
all these transformations might not be
worth.

203
00:15:44,664 --> 00:15:51,410
and the vision is more to operate with
hydrogen or electric power,

204
00:15:51,411 --> 00:15:56,471
more with what you call this fuel cell
system.

205
00:15:56,472 --> 00:15:58,720
So you can provide

206
00:15:58,721 --> 00:16:04,644
hydrogen and then you can produce electric
power from the fuel cell.

207
00:16:04,645 --> 00:16:10,568
So that for the short range in the order
of 1,000 kilometers

208
00:16:10,569 --> 00:16:14,517
and long, it's a solution that it's really

209
00:16:14,518 --> 00:16:16,320
the

210
00:16:16,321 --> 00:16:23,821
ambition in the sector. For mid-range and
long-range, the electric solution is

211
00:16:24,057 --> 00:16:31,557
not feasible today and then solutions
based on hydrogen are coming to...

212
00:16:31,794 --> 00:16:37,320
have a share. The main solution for
decarbonization in the aviation at

213
00:16:37,321 --> 00:16:42,846
the moment is what they call sustainable
aviation fuels that are replacement

214
00:16:42,847 --> 00:16:47,912
fuels that they have similar properties
and similar behavior as the

215
00:16:47,913 --> 00:16:53,438
conventional aviation fuels. Then if we
move quickly to other sectors like

216
00:16:53,439 --> 00:16:58,503
furnaces or boilers or industrial
applications, we are involved in several

217
00:16:58,504 --> 00:17:01,727
projects on this field also beyond
aviation.

218
00:17:01,967 --> 00:17:07,901
And then there has been quite a lot of
progress.

219
00:17:07,902 --> 00:17:15,022
There has been demonstrators of partners
that can buy hydrogen in steel

220
00:17:15,023 --> 00:17:20,363
manufacturing or metallurgical sector,
glass manufacturing also, and solutions

221
00:17:20,364 --> 00:17:23,923
based on hydrogen are actually possible.

222
00:17:23,924 --> 00:17:29,857
The question with hydrogen is the price of
the hydrogen.

223
00:17:30,063 --> 00:17:34,505
and the availability and how much hydrogen
you can give me and

224
00:17:34,506 --> 00:17:38,947
at which price. This is more or less what
these sectors are

225
00:17:38,948 --> 00:17:40,428
wondering at the moment.

226
00:17:40,429 --> 00:17:45,393
Hmm, okay. So it sounds like it's, but if
you look at,

227
00:17:45,394 --> 00:17:49,116
and apologies if this is a stupid
question, but

228
00:17:49,297 --> 00:17:50,597
No.

229
00:17:50,598 --> 00:17:56,801
the jet engine obviously has been heavily
optimized for a particular fuel

230
00:17:56,802 --> 00:18:03,005
type over decades. From a jet engine point
of view, how different

231
00:18:03,006 --> 00:18:07,658
does the design have to be to take
hydrogen?

232
00:18:07,659 --> 00:18:11,511
I mean, isn't it a completely different
engine essentially?

233
00:18:11,512 --> 00:18:16,649
Or are you saying that it's more of a, you
know, partial

234
00:18:16,650 --> 00:18:21,787
change within the combustor, but maybe the
other bits or is it,

235
00:18:21,788 --> 00:18:26,925
does the whole thing essentially start to
change because of the different

236
00:18:26,926 --> 00:18:29,494
power requirements or weight or sizing?

237
00:18:29,495 --> 00:18:34,269
Yes, in fact, this is a very good question
and it is

238
00:18:34,270 --> 00:18:39,044
a little bit unclear depending on who you
talk to or Who

239
00:18:39,045 --> 00:18:43,421
you read from then you can get a slightly
different answer.

240
00:18:43,422 --> 00:18:48,195
So putting more or less everything on the
table a You can

241
00:18:48,196 --> 00:18:52,572
burn hydrogen in a conventional
conventional aircraft engine that has been

242
00:18:52,573 --> 00:18:57,347
more or less demonstrated the problem is
that Aircraft engines or jet

243
00:18:57,348 --> 00:18:57,746
engines

244
00:18:57,746 --> 00:19:02,269
they operate with liquid fuels. So the
injector must be different.

245
00:19:02,270 --> 00:19:06,382
There are aeronautical injectors that can
inject the gaseous fuels.

246
00:19:06,383 --> 00:19:11,318
You can store hydrogen as liquid, but as
soon as they approach

247
00:19:11,319 --> 00:19:16,253
to the combustion chamber with all the
passages and everything, it's going

248
00:19:16,254 --> 00:19:19,955
to evaporate. So very likely it's going to
have

249
00:19:20,085 --> 00:19:20,793
so changes in

250
00:19:20,794 --> 00:19:24,024
the engine to accommodate hydrogen fuel.

251
00:19:24,025 --> 00:19:30,487
So the first is the injector. The injector
is a conventional jet

252
00:19:30,488 --> 00:19:36,411
engine operated with liquid fuel, so the
injector must be different.

253
00:19:36,412 --> 00:19:42,874
There are gaseous aeronautical injectors,
so that's not a problem, but yeah,

254
00:19:42,875 --> 00:19:45,567
something needs to be adapted.

255
00:19:45,568 --> 00:19:50,605
So even though the hydrogen, for people
who are very experts, they

256
00:19:50,606 --> 00:19:55,642
say, okay, but you store the hydrogen as
liquid in the tank.

257
00:19:55,643 --> 00:20:00,680
Yes, but through the delivery of the fuel
through the pipes are

258
00:20:00,681 --> 00:20:05,718
going to be preheated and you are gonna
lower the pressure partially.

259
00:20:05,719 --> 00:20:10,756
And then when you are injecting directly
in the combustion chamber, then

260
00:20:10,757 --> 00:20:14,534
this is a very hot environment. So partial
evaporation.

261
00:20:14,754 --> 00:20:20,841
is going to happen and this is an active
area of research

262
00:20:20,842 --> 00:20:24,392
so the problem is not actually solved.

263
00:20:24,393 --> 00:20:30,480
This is on one side from the conventional
RQL which is the

264
00:20:30,481 --> 00:20:34,538
technology for aero engines this is like a

265
00:20:34,539 --> 00:20:39,332
like the piston engine, so pretty much any
fuel you burn it,

266
00:20:39,333 --> 00:20:44,127
okay? Because in the RQL, you have a
primary fuel injection, you

267
00:20:44,128 --> 00:20:48,921
have dilution with the quenching, and then
you have the secondary combustion

268
00:20:48,922 --> 00:20:52,916
happening. With this, you pretty much can
burn any fuel.

269
00:20:52,917 --> 00:20:56,512
The question is, how efficient you burn
the hydrogen?

270
00:20:56,513 --> 00:21:02,769
How many unburned hydrogen are you going
to produce with the design

271
00:21:02,770 --> 00:21:09,026
of a combustion chamber that, as you
mentioned, has been optimized for

272
00:21:09,027 --> 00:21:13,197
many years to burn hydrogen, to burn
kerosene?

273
00:21:13,198 --> 00:21:17,368
So would that be enough to satisfy
regulations?

274
00:21:17,369 --> 00:21:23,104
Well, could be. You don't have CO2, you
don't have particulates.

275
00:21:23,105 --> 00:21:28,452
you don't have many of the other compounds
CO in your fuel.

276
00:21:28,453 --> 00:21:33,355
What about the NOx? The NOx will depend on
the temperatures.

277
00:21:33,356 --> 00:21:38,703
If you reach high temperatures, then it's
very likely that you will

278
00:21:38,704 --> 00:21:44,051
have troubles with the NOx. If you manage
to mix well, then

279
00:21:44,052 --> 00:21:49,399
your NOx will be okay. But changes in the
combustion chamber would

280
00:21:49,400 --> 00:21:51,182
be required in order

281
00:21:51,373 --> 00:21:56,548
to have an optimal combustion system for
hydrogen, but not also on

282
00:21:56,549 --> 00:21:59,998
the jet engine, but also on the aircraft.

283
00:21:59,999 --> 00:22:05,173
The tanks must have to be different, the
delivery of the fuel

284
00:22:05,174 --> 00:22:10,348
as well to accommodate the pressure, to
accommodate the fuel must be

285
00:22:10,349 --> 00:22:11,642
different as well.

286
00:22:11,643 --> 00:22:16,330
feels almost equivalent in the automotive
sector when initially people just

287
00:22:16,331 --> 00:22:21,443
said, well, let's just pull out the engine
and put batteries where

288
00:22:21,444 --> 00:22:23,148
the engine was, but

289
00:22:23,149 --> 00:22:28,232
everything the same. And I think almost
everybody realized that that was

290
00:22:28,233 --> 00:22:33,316
not the optimum solution. And actually all
the modern day electric vehicles

291
00:22:33,317 --> 00:22:35,434
are designed from the beginning.

292
00:22:35,566 --> 00:22:39,644
and you see things like the batteries are
on the bottom, you

293
00:22:39,645 --> 00:22:43,722
know, rather than in the front. you know,
there's like different ways.

294
00:22:43,723 --> 00:22:47,800
And I can only imagine on an aircraft that
ultimately you would

295
00:22:47,801 --> 00:22:51,878
want to design the system entirely based
around that new fuel type.

296
00:22:51,879 --> 00:22:57,139
Exactly, is exactly the case. So in fact,
how the aviation sector

297
00:22:57,140 --> 00:23:02,400
works is that they have the airplane and
they make a call

298
00:23:02,401 --> 00:23:07,660
for having what is the most appropriate
engine that can work, can

299
00:23:07,661 --> 00:23:09,414
go on that aircraft.

300
00:23:09,620 --> 00:23:14,863
in this case is the same. So if your
engine operates with

301
00:23:14,864 --> 00:23:19,232
hydrogen, that cannot be a solution for
all the aircraft.

302
00:23:19,233 --> 00:23:24,475
So in the end, an optimal aircraft will
have a design of

303
00:23:24,476 --> 00:23:29,718
the whole aircraft associated to
accommodate the fuel and to accommodate the

304
00:23:29,719 --> 00:23:34,961
engine. And then, of course, you can plug
in the appropriate engine

305
00:23:34,962 --> 00:23:39,767
and everything will be optimized. But
yeah, it's exactly the same.

306
00:23:39,768 --> 00:23:41,042
as you mentioned, yes.

307
00:23:41,650 --> 00:23:46,280
And I feel like the past 40 years has
essentially been that

308
00:23:46,281 --> 00:23:50,911
where it's like, we'll still just go for
the tube and two

309
00:23:50,912 --> 00:23:55,541
wings because it kind of works and we
don't want to rock

310
00:23:55,542 --> 00:24:00,171
the boat. And so it'd be interesting on
the fuel type how

311
00:24:00,172 --> 00:24:02,872
much, you say, because planes operate
globally.

312
00:24:02,873 --> 00:24:07,503
When that's what my question, when will
they actually go, let's go

313
00:24:07,504 --> 00:24:09,818
for it and do the hydrogen.

314
00:24:09,819 --> 00:24:14,460
what needs to change commercially for that
to be the switchover point.

315
00:24:14,461 --> 00:24:19,102
Like electric vehicles, there was this
like switchover point and now I

316
00:24:19,103 --> 00:24:21,423
think it's switching over, isn't it?

317
00:24:21,424 --> 00:24:26,829
Exactly, exactly. But I think this is
exactly the situation, what we

318
00:24:26,830 --> 00:24:28,180
should not forget...

319
00:24:28,181 --> 00:24:34,307
is that the technology required to design
a jet engine and to

320
00:24:34,308 --> 00:24:40,433
operate safely across a wide range of
operating conditions, the fly envelope

321
00:24:40,434 --> 00:24:46,560
and all that, is extremely demanding. And
also the certification process is

322
00:24:46,561 --> 00:24:52,687
also very long, very tedious, and then not
all the products that

323
00:24:52,688 --> 00:24:58,303
seem to work can be finally commercialized
because the safety requirements

324
00:24:58,304 --> 00:25:01,026
for these products are not like the car.

325
00:25:01,027 --> 00:25:05,112
So the car stops in the highway and then
you just stop

326
00:25:05,113 --> 00:25:09,197
and you call some help. But on the
airplane, if you have

327
00:25:09,198 --> 00:25:13,282
problem on the fly, then in the sky, then
you are in

328
00:25:13,283 --> 00:25:15,665
big trouble. So nobody is gonna come

329
00:25:15,666 --> 00:25:20,576
and help you. I think this is why even
the, I mean,

330
00:25:20,577 --> 00:25:25,487
our contacts with the Aeroengine
manufacturers, you can see that they are

331
00:25:25,488 --> 00:25:27,943
really pushing and they are really

332
00:25:27,983 --> 00:25:32,017
interested in developing the technology.
However, the horizon for hydrogen is

333
00:25:32,018 --> 00:25:36,418
very, very unclear and it's not to sit on
the same table

334
00:25:36,419 --> 00:25:40,819
because I'm a scientist. It is true that
it's not clear what

335
00:25:40,820 --> 00:25:45,220
is going to be the price of hydrogen. And
even if the

336
00:25:45,221 --> 00:25:48,888
price is acceptable, then the question is
how much hydrogen?

337
00:25:48,889 --> 00:25:53,289
So an aircraft needs a lot of fuel. Only
the takeoff needs,

338
00:25:53,290 --> 00:25:57,690
I don't know, how many thousands of
kilograms of fuel you need

339
00:25:57,691 --> 00:25:58,423
for takeoff.

340
00:25:58,424 --> 00:26:03,231
So, and it takes only a minutes. So then
how this is

341
00:26:03,232 --> 00:26:07,639
going to happen? So many aircrafts are
going to use hydrogen.

342
00:26:07,640 --> 00:26:12,448
You need a huge amount of hydrogen
available at the airport in

343
00:26:12,449 --> 00:26:14,451
storage and infrastructure. So I

344
00:26:14,452 --> 00:26:19,875
think this cannot be rushed and this needs
to be done carefully.

345
00:26:19,876 --> 00:26:24,396
And I think this is what is the status
today.

346
00:26:24,397 --> 00:26:28,012
So technologies are being developed, but
the infrastructure

347
00:26:28,013 --> 00:26:34,157
to operate this in a sustainable way, I
think it still misses

348
00:26:34,158 --> 00:26:34,669
quite

349
00:26:34,829 --> 00:26:36,692
some years.

350
00:26:36,693 --> 00:26:41,193
So maybe turning on the point which I
guess both of us

351
00:26:41,194 --> 00:26:45,694
work on, which is this dream of, you know,
why does it

352
00:26:45,695 --> 00:26:48,695
take 10 years for aerospace projects or
longer?

353
00:26:48,696 --> 00:26:53,196
And one of the reasons or hypothesis that
we have is that

354
00:26:53,197 --> 00:26:57,697
if we can increasingly use more accurate
simulation tools, then we can

355
00:26:57,698 --> 00:27:02,199
help them to move faster because they
frankly need to rely a

356
00:27:02,200 --> 00:27:03,699
little bit less on.

357
00:27:03,700 --> 00:27:09,419
experimental methods and they can
potentially explore and do more what-if

358
00:27:09,420 --> 00:27:15,660
scenarios. So on that point, today, to the
best of your understanding,

359
00:27:15,661 --> 00:27:21,900
let's maybe zoom into the CFD side of
things a little bit

360
00:27:21,901 --> 00:27:28,141
more. If you're doing combustion of a
conventional hydrocarbon jet engine or

361
00:27:28,142 --> 00:27:29,181
a hydrogen.

362
00:27:29,182 --> 00:27:34,230
Where would you, what would be the typical
CFD approach and where

363
00:27:34,231 --> 00:27:39,279
would you classify in terms of their trust
of the method in

364
00:27:39,280 --> 00:27:42,225
terms of accuracy, in terms of
correlation?

365
00:27:42,226 --> 00:27:46,012
Where do we stand today? How pleased are
they?

366
00:27:46,013 --> 00:27:51,061
How far away are they away from methods
that they can trust?

367
00:27:51,062 --> 00:27:57,205
Okay, this is a good point and in fact
this is quite...

368
00:27:57,206 --> 00:28:04,174
a good feature for engineers that they
like combustion systems and engines,

369
00:28:04,175 --> 00:28:11,142
but also other type of applications from
fluid mechanics, not only these

370
00:28:11,143 --> 00:28:16,369
applications about aerodynamics or other
other type of flows.

371
00:28:16,370 --> 00:28:23,337
For combustion, there is a lot of things
going on on this

372
00:28:23,338 --> 00:28:23,918
because

373
00:28:23,919 --> 00:28:28,474
The CFD part of the combustion system is
very important today.

374
00:28:28,475 --> 00:28:33,029
But not only for one part of the whole
product development.

375
00:28:33,030 --> 00:28:37,999
At the start, so combustion is, I would
say, I don't want

376
00:28:38,000 --> 00:28:42,969
to give a percentage, but let me just be,
it's very important,

377
00:28:42,970 --> 00:28:46,697
the injection system. The injection system
is the start.

378
00:28:46,698 --> 00:28:51,666
So how you inject the fuel is one of the
most important

379
00:28:51,667 --> 00:28:53,323
components of the engine.

380
00:28:53,324 --> 00:28:58,638
doesn't matter which or not even engine in
any combustion system because

381
00:28:58,639 --> 00:29:03,954
you can only burn a fuel that is has
already mixed with

382
00:29:03,955 --> 00:29:09,269
air with oxygen you don't need air you
need oxygen you only

383
00:29:09,270 --> 00:29:14,585
need oxygen so how you can end up having a
mixture of

384
00:29:14,586 --> 00:29:19,900
fuel with oxygen so and that is maybe 80
90 percent because

385
00:29:19,901 --> 00:29:21,229
of the injector

386
00:29:21,230 --> 00:29:25,954
And of course, a part related to the
geometry of the combustor.

387
00:29:25,955 --> 00:29:28,711
But it's mainly related to the injector.

388
00:29:28,712 --> 00:29:33,436
I'm thinking of supersonic combustion in
which the geometry of the combustor

389
00:29:33,437 --> 00:29:36,586
has to facilitate because everything
happens very fast.

390
00:29:36,587 --> 00:29:40,918
But for other type of applications, the
injector is very, important.

391
00:29:40,919 --> 00:29:44,462
It's the most important thing, especially
with liquid fuels.

392
00:29:44,463 --> 00:29:49,187
Because you have to atomize the fuel. You
have to break the

393
00:29:49,188 --> 00:29:49,582
liquid.

394
00:29:49,582 --> 00:29:54,481
the liquid core and this breaks into
ligaments.

395
00:29:54,482 --> 00:29:58,769
These ligaments are broken into smaller
ligaments.

396
00:29:58,770 --> 00:30:04,282
Finally, they form droplets and these
droplets finally evaporate.

397
00:30:04,283 --> 00:30:08,570
You don't evaporate a whole liquid core.

398
00:30:08,571 --> 00:30:15,921
So in this process, for the injector, with
additive manufacturing, is a

399
00:30:15,922 --> 00:30:19,596
revolution for the fill in combustion.

400
00:30:19,597 --> 00:30:24,250
So you can have very complicated designs
of the injector thanks to

401
00:30:24,251 --> 00:30:28,903
the additive manufacturing. And then
before you take them to the lab,

402
00:30:28,904 --> 00:30:33,557
you should do some CFD. Because if your
CFD can show that

403
00:30:33,558 --> 00:30:38,211
you're not breaking the liquid film, and
then you get a very

404
00:30:38,212 --> 00:30:42,864
long liquid sheet and it's not broken,
what's the point to do

405
00:30:42,865 --> 00:30:47,518
an experiment? So you can save a lot of
money by just

406
00:30:47,519 --> 00:30:49,069
having an initial stage.

407
00:30:49,070 --> 00:30:55,379
of CFD analysis of injection. Injection
and then evaluating the spray

408
00:30:55,380 --> 00:31:02,262
characteristics. Then after that you go to
evaporation and then you go

409
00:31:02,263 --> 00:31:09,145
to combustion. Okay, so you can
discriminate a lot of designs by

410
00:31:09,146 --> 00:31:14,881
a first filter based on CFD. And then
after that,

411
00:31:14,882 --> 00:31:19,381
You can take this to the lab and then you
can do

412
00:31:19,382 --> 00:31:23,882
the measurements, you can correlate, and
then you can do this discrimination.

413
00:31:23,883 --> 00:31:28,382
For that, you can rely, and this is
something that you have

414
00:31:28,383 --> 00:31:32,883
worked a lot, Anil, I know, on which
technique do I use?

415
00:31:32,884 --> 00:31:37,383
Do I use RANs or do I use LES? Do I use

416
00:31:37,384 --> 00:31:41,884
DNS? DNS, definitely, we don't use it for
design, but LES today

417
00:31:41,885 --> 00:31:43,009
is very competitive.

418
00:31:43,010 --> 00:31:48,690
I don't want to do some advertisement
here, but our code, you

419
00:31:48,691 --> 00:31:54,371
can solve today with supercomputers, with
HPC, you can solve a problem

420
00:31:54,372 --> 00:31:59,579
of combustion or the fuel injection in 10
hours, 12 hours.

421
00:31:59,580 --> 00:32:05,260
I mean, you cannot get all the statistics,
but you can actually

422
00:32:05,261 --> 00:32:10,942
get some LES in 24 hours that give you
enough statistics for

423
00:32:10,943 --> 00:32:12,362
discrimination of designs.

424
00:32:12,363 --> 00:32:16,145
And then you can submit multiple jobs at
the same time if

425
00:32:16,146 --> 00:32:19,928
you have your cluster. And then you can,
you you leave the

426
00:32:19,929 --> 00:32:23,081
office like at five o'clock in like in the
UK.

427
00:32:23,082 --> 00:32:25,287
Spain probably leave a little bit later.

428
00:32:25,288 --> 00:32:29,070
But then the day after at nine o'clock,
you pretty much have

429
00:32:29,071 --> 00:32:30,016
20, 25 designs

430
00:32:30,017 --> 00:32:34,772
already available for you to check the
results.

431
00:32:34,773 --> 00:32:41,905
So for that is important. And then another
core part of where

432
00:32:42,077 --> 00:32:47,903
simulations are very important is when you
do at high TRL designs

433
00:32:47,904 --> 00:32:53,729
of the engine which is for example one of
the minor problems

434
00:32:53,730 --> 00:32:59,555
in combustion is pressure okay and maybe
we can discuss that at

435
00:32:59,556 --> 00:33:05,381
some point later but when you go in
pressure then the flame

436
00:33:05,382 --> 00:33:11,207
becomes very compact becomes very reactive
very energetic and then it can

437
00:33:11,208 --> 00:33:11,694
be

438
00:33:11,694 --> 00:33:18,117
very difficult to simulate and it can be
very difficult to model.

439
00:33:18,118 --> 00:33:24,541
So relying on brands is less, at this
point is a little

440
00:33:24,542 --> 00:33:30,965
bit less reliable. So switching to Elias
is what most of the,

441
00:33:30,966 --> 00:33:36,318
well, most of the manufacturers are trying
to shift nowadays.

442
00:33:36,319 --> 00:33:40,065
I'm saying shifting when they have
already.

443
00:33:40,066 --> 00:33:45,132
done it but some of them, the smaller
companies might not do

444
00:33:45,133 --> 00:33:50,200
LES today for that but the large companies
they of course they

445
00:33:50,201 --> 00:33:55,267
do LES and this has gone to a point where
some of

446
00:33:55,268 --> 00:34:00,335
the high pressure tests that you can do in
the lab and

447
00:34:00,336 --> 00:34:05,402
they are extremely expensive because of
the equipment, because of the room,

448
00:34:05,403 --> 00:34:08,358
because of the fuel you when you

449
00:34:08,359 --> 00:34:13,590
the pressure, the amount of kilograms per
second that you have in

450
00:34:13,591 --> 00:34:18,822
your injector is very high, the fuel is
not cheap, especially if

451
00:34:18,823 --> 00:34:24,054
you consider hydrogen, so doing tests at 5
bar or 10 bar

452
00:34:24,055 --> 00:34:29,286
is extremely expensive in the orders of
many thousands of euros per

453
00:34:29,287 --> 00:34:34,518
day of testing, so this can be partially
substituted by doing high

454
00:34:34,519 --> 00:34:35,390
fidelity CFD.

455
00:34:35,391 --> 00:34:40,175
And many of the big companies nowadays,
they have a strategy to

456
00:34:40,176 --> 00:34:44,960
discriminate and to not even do high
pressure tests because they rely

457
00:34:44,961 --> 00:34:49,745
substantially on their CFD. Of course, at
the end, the product reaches

458
00:34:49,746 --> 00:34:53,732
certain maturity, of course, you have to
do the tests.

459
00:34:53,733 --> 00:34:58,517
But during the early stages, until you get
to that point, then

460
00:34:58,518 --> 00:35:01,707
you can save a huge amount of time.

461
00:35:01,708 --> 00:35:05,237
by running these simulations. But these
simulations are very special, so you

462
00:35:05,238 --> 00:35:08,472
need to be very careful about this. What
are your numerics?

463
00:35:08,473 --> 00:35:10,897
What are your models? And where do

464
00:35:11,145 --> 00:35:15,340
where is the what's the bit that affects
the accuracy the most

465
00:35:15,341 --> 00:35:19,535
so if they're doing an ls of the injection
system or the

466
00:35:19,536 --> 00:35:22,681
combustion What's the bit that would
affect the accuracy?

467
00:35:22,682 --> 00:35:25,477
What's the gap between that and a dns?

468
00:35:25,478 --> 00:35:28,973
What are the bits that? You know are still
lacking

469
00:35:28,974 --> 00:35:35,337
Hmm. Yeah, that's a very good point. And I
think I'm a

470
00:35:35,338 --> 00:35:41,701
little bit biased to give you the answer
because I'm more into

471
00:35:41,702 --> 00:35:47,004
alias, not that DNS. For me, DNS is more
phenomenological.

472
00:35:47,005 --> 00:35:53,368
So you don't really need to have a DNS of
an aircraft

473
00:35:53,369 --> 00:35:59,201
engine to extract the information that you
want from these simulations.

474
00:35:59,202 --> 00:36:03,738
because I think this is the key answer
that I can give

475
00:36:03,739 --> 00:36:07,519
you. So it depends on what you want to
get.

476
00:36:07,520 --> 00:36:10,922
So what is exactly what you want to learn?

477
00:36:10,923 --> 00:36:15,460
So in the aero engine sector, that this is
what we have

478
00:36:15,461 --> 00:36:19,997
mainly focused the discussion. I think we
can keep it like this.

479
00:36:19,998 --> 00:36:24,535
It's representative to most of the
combustion applications and it brings some

480
00:36:24,536 --> 00:36:27,181
additional also challenges compared to
other systems.

481
00:36:27,182 --> 00:36:29,450
So in the aero engine, everything

482
00:36:29,451 --> 00:36:34,896
I would say it's related to safety. You
don't want to have

483
00:36:34,897 --> 00:36:40,341
flashbacks. You don't want the flame to
propagate or to touch the

484
00:36:40,342 --> 00:36:45,333
wall and break anything. So stability is
one of the priorities.

485
00:36:45,334 --> 00:36:48,509
But usually it's the balance between
thermoacoustics.

486
00:36:48,510 --> 00:36:53,047
You have the acoustic waves interacting
with the heat release.

487
00:36:53,048 --> 00:36:58,039
This gets into a feedback loop that
creates the thermoacoustic instability.

488
00:36:58,040 --> 00:37:02,600
that is one of the most dangerous
phenomena that can happen in

489
00:37:02,601 --> 00:37:07,161
an engine. And that is what drives a
little bit the early

490
00:37:07,162 --> 00:37:10,962
stages of the design and of course until
the end.

491
00:37:10,963 --> 00:37:15,523
the thermoacoustic instability is
something to be avoided and to be checked.

492
00:37:15,524 --> 00:37:20,084
And the complexity of this phenomena is
the fact that it is

493
00:37:20,085 --> 00:37:24,645
highly dependent on the geometry. So if
you simplify the geometry to

494
00:37:24,646 --> 00:37:26,925
do your test, because I mean...

495
00:37:26,926 --> 00:37:30,945
We always talk about challenges for CFD
because we have many and

496
00:37:30,946 --> 00:37:34,965
people know that we have many and we
always have to justify

497
00:37:34,966 --> 00:37:37,645
us. But in the experiments it's the same.

498
00:37:37,646 --> 00:37:41,666
An aero engine is not flat. But when they
measure with the

499
00:37:41,667 --> 00:37:44,011
laser, they need to put straight windows.

500
00:37:44,012 --> 00:37:47,361
So doing measurements in rounded domains
is much more complex.

501
00:37:47,362 --> 00:37:50,376
You need two mirrors, you need some
specific equipment.

502
00:37:50,377 --> 00:37:52,721
So they prefer to have the injector.

503
00:37:52,951 --> 00:37:57,589
They put the two windows, they are flat,
you measure with the

504
00:37:57,590 --> 00:38:01,068
laser and then you get all the fancy
stuff.

505
00:38:01,069 --> 00:38:05,320
So that configuration tells you almost
nothing about thermoacoustics in the

506
00:38:05,321 --> 00:38:06,093
engine. So

507
00:38:06,094 --> 00:38:09,972
then you have to work with the whole
geometry.

508
00:38:09,973 --> 00:38:14,281
And then the other aspect is of course the
emissions.

509
00:38:14,282 --> 00:38:19,022
So you need to deal with the potential
emissions, particulate formation.

510
00:38:19,023 --> 00:38:22,647
You need to deal... CO2 is the
consequence.

511
00:38:22,648 --> 00:38:28,084
If everything is perfect, you produce CO2,
but you need to deal

512
00:38:28,085 --> 00:38:33,521
with CO, NOx... These are the main things
in a pure fuel

513
00:38:33,522 --> 00:38:38,958
and then the particulates. So you need to
account for all these

514
00:38:38,959 --> 00:38:42,130
things when you are designing the engine.

515
00:38:42,131 --> 00:38:47,197
And in terms of now the actual CFD
running, what's the computational

516
00:38:47,198 --> 00:38:52,263
cost? it the solver, the chemistry, the
load balancing, the IO, the

517
00:38:52,264 --> 00:38:57,330
like, what drives the, if you were to
profile the code, what

518
00:38:57,331 --> 00:39:02,397
do you kind of see as the main bits? Cause
I guess

519
00:39:02,398 --> 00:39:07,464
the chemistry and the species is the key
difference between that and

520
00:39:07,465 --> 00:39:09,997
some incompressible, you know, car flow.

521
00:39:09,998 --> 00:39:14,806
Yes, exactly. as you said, so in the end,
if we go,

522
00:39:14,807 --> 00:39:19,615
if we forget about models, because at the
end, the community, I

523
00:39:19,616 --> 00:39:23,623
mean, is not stupid. mean, in fact, we are
smart.

524
00:39:23,624 --> 00:39:28,031
So we develop models for things that are
complicated to resolve.

525
00:39:28,032 --> 00:39:31,237
So if we cannot resolve, we model, no?

526
00:39:31,238 --> 00:39:32,439
This is the...

527
00:39:32,440 --> 00:39:32,918
you

528
00:39:32,918 --> 00:39:37,886
the idea that we have. So if we forget
about models and

529
00:39:37,887 --> 00:39:42,855
we think about our system, the number of
unknowns and the conservation

530
00:39:42,856 --> 00:39:47,824
equations, at the end is the conventional
fluid mechanics we solve for

531
00:39:47,825 --> 00:39:52,793
the continuity, the momentum and the
energy equation like in the conventional

532
00:39:52,794 --> 00:39:56,106
fluid mechanics community, at least in the
compressible.

533
00:39:56,107 --> 00:40:00,661
But then we need to solve equations for
the chemical species.

534
00:40:00,662 --> 00:40:01,489
So the...

535
00:40:01,490 --> 00:40:07,437
more complex the fuel, the more number of
species is usually attached

536
00:40:07,438 --> 00:40:13,385
to this, because you need to describe all
the possible chemical pathways

537
00:40:13,386 --> 00:40:19,333
that the individual molecules can have
after the interactions with all these

538
00:40:19,334 --> 00:40:22,307
radicals. So that introduces certain cost.

539
00:40:22,308 --> 00:40:28,255
you solve, I don't know, for hydrogen with
nine species, you can

540
00:40:28,256 --> 00:40:29,742
describe the chemistry.

541
00:40:29,743 --> 00:40:34,992
But for methane or for a hydrocarbon fuel,
C1 with one carbon,

542
00:40:34,993 --> 00:40:40,243
the more carbons you have in the fuel, the
more potential chemical

543
00:40:40,244 --> 00:40:45,493
pathways you are going to have and the
more species is very

544
00:40:45,494 --> 00:40:50,306
likely that you are going to need to
describe this properly.

545
00:40:50,307 --> 00:40:51,181
And then...

546
00:40:51,182 --> 00:40:55,624
The number of species can go from 23, 25,
30, 40, 50,

547
00:40:55,625 --> 00:41:00,067
60, 100. If the fuel is complex, like a
kerosene or like

548
00:41:00,068 --> 00:41:04,510
a gasoline or a diesel or something like
that, to describe this,

549
00:41:04,511 --> 00:41:08,954
you can have hundreds of species. So then
the cost of solving

550
00:41:08,955 --> 00:41:12,286
the Navier-Stokes is completely
irrelevant. So this costs nothing.

551
00:41:12,287 --> 00:41:15,618
Ah, but I'm not very efficient with my
Navier-Stokes.

552
00:41:15,619 --> 00:41:18,210
Okay, no problem. You have 200 species.

553
00:41:18,211 --> 00:41:19,321
So Navier-Stokes is

554
00:41:19,322 --> 00:41:21,876
five equations more on 200.

555
00:41:21,877 --> 00:41:27,862
But usually, this is still not the source
of the cost of

556
00:41:27,863 --> 00:41:33,847
the simulation. The cost of the simulation
mainly comes from the computation

557
00:41:33,848 --> 00:41:36,341
of the chemical source term.

558
00:41:36,342 --> 00:41:41,306
And I'm going to try to explain this.
People can find this

559
00:41:41,307 --> 00:41:46,272
information anywhere because it's very
well known and it's very well accepted

560
00:41:46,273 --> 00:41:51,237
that this is the challenge. So the problem
is that the chemical

561
00:41:51,238 --> 00:41:56,202
source term, you have a chemical source
term in each equation of

562
00:41:56,203 --> 00:42:01,168
the species. But this particular species,
for example, if we think about

563
00:42:01,169 --> 00:42:06,133
hydrogen as a chemical species, H2
molecule can participate in many reactions.

564
00:42:06,134 --> 00:42:10,676
So it does not appear in two or three
reactions.

565
00:42:10,677 --> 00:42:14,765
It can appear in maybe 10 or 20 reactions.

566
00:42:14,766 --> 00:42:20,216
So then the chemical source terms depend
on the reaction rate that

567
00:42:20,217 --> 00:42:25,668
can have this chemical species when
participates in all these 10 or

568
00:42:25,669 --> 00:42:28,848
20 reactions. So it becomes extremely
nonlinear.

569
00:42:28,849 --> 00:42:34,299
But the point is that when you want to
calculate the chemical

570
00:42:34,300 --> 00:42:35,662
source term, this

571
00:42:35,663 --> 00:42:40,316
these chemical reactions depend on the
temperature, but the temperature

572
00:42:40,317 --> 00:42:45,900
depends on the flow. So you cannot, a
priori, you cannot separate

573
00:42:45,901 --> 00:42:51,020
the chemical source term from the
transporting and the conservation equations

574
00:42:51,021 --> 00:42:53,812
because this chemical source term depends

575
00:42:53,813 --> 00:42:57,001
on the temperature and depends on the
local composition.

576
00:42:57,002 --> 00:43:01,253
So if this source term goes a little bit
higher, the concentration

577
00:43:01,254 --> 00:43:04,087
of that species go a little bit higher.

578
00:43:04,088 --> 00:43:08,461
so the chemical source time changes. So
you need to solve everything

579
00:43:08,462 --> 00:43:12,834
at the same time. So in fact, you can
decouple and this

580
00:43:12,835 --> 00:43:15,750
is called a splitting method or splitting
operators.

581
00:43:15,751 --> 00:43:20,124
There are approximations that can try to
decouple things so you can

582
00:43:20,125 --> 00:43:24,498
solve things separated. But in the end, in
practice, you need to

583
00:43:24,499 --> 00:43:28,872
solve them all together. So you need to
iterate in your source

584
00:43:28,873 --> 00:43:29,965
term in order.

585
00:43:30,189 --> 00:43:36,435
to have the correct chemical substance
that is consistent with your

586
00:43:36,436 --> 00:43:43,249
thermochemical state. And then the problem
is associated to the time scales

587
00:43:43,250 --> 00:43:50,063
because there are species that move very
slow, like CO2 progresses very

588
00:43:50,064 --> 00:43:56,877
slow through the evolution of the chemical
reactions, but also you have...

589
00:43:56,878 --> 00:44:02,274
radicals that they are produced very
rapidly and consumed very rapidly.

590
00:44:02,275 --> 00:44:08,162
If you don't capture the production and
consumption, you are not able

591
00:44:08,163 --> 00:44:14,051
to predict certain phenomena that could be
very important for your combustor.

592
00:44:14,052 --> 00:44:19,939
For example, ignition or extinction or
this kind of transient events that

593
00:44:19,940 --> 00:44:23,373
can dominate what happens in your
combustor.

594
00:44:23,374 --> 00:44:25,336
So because of that,

595
00:44:25,337 --> 00:44:31,852
dealing with the disparity of the time
scales, dealing with multiple species

596
00:44:31,853 --> 00:44:38,367
and dealing with the treatment of the
chemical source term is what

597
00:44:38,368 --> 00:44:43,254
has mainly concentrated all the turbulent
combustor modeling historically,

598
00:44:43,255 --> 00:44:43,797
basically.

599
00:44:43,798 --> 00:44:48,680
And am I right, before we get into the
topic of GPUs,

600
00:44:48,681 --> 00:44:52,750
wall modeling is not such a first order
effect, right?

601
00:44:52,751 --> 00:44:57,633
Would that be fair to say? Like, I know
you don't want

602
00:44:57,634 --> 00:45:02,516
the flame to touch the walls. I know the
walls have an

603
00:45:02,517 --> 00:45:06,179
impact from a sort of acoustics, et
cetera, but.

604
00:45:06,180 --> 00:45:10,742
Is sort of wall modeled LES a more
acceptable thing?

605
00:45:10,743 --> 00:45:16,218
Can you be using like wall functions or
how much does resolving

606
00:45:16,219 --> 00:45:20,781
the boundary layers and the wall, how
important is that?

607
00:45:20,782 --> 00:45:25,920
Okay, this is a very good point because
I'm facing this problem

608
00:45:25,921 --> 00:45:31,058
at the moment. In general, it depends
again to exactly what you

609
00:45:31,059 --> 00:45:36,197
want. If you want to understand if the
flame is stable or

610
00:45:36,198 --> 00:45:41,336
not, then if you have a very compact flame
in the middle

611
00:45:41,337 --> 00:45:43,905
and your combustor is very big,

612
00:45:43,906 --> 00:45:48,380
Having the best wall model that reproduces
all the effects on these

613
00:45:48,381 --> 00:45:52,855
side walls is not that relevant if you are
interested in understanding

614
00:45:52,856 --> 00:45:57,330
if the flame is stable or not. But you
need to resolve

615
00:45:57,331 --> 00:46:01,804
the boundary layer in case that you are
considering the possibility of

616
00:46:01,805 --> 00:46:06,279
flashback. If the flame is lifted, at the
end, all the injection

617
00:46:06,280 --> 00:46:10,754
ports and everything that you have
upstream, the combustion chamber, can be

618
00:46:10,755 --> 00:46:11,255
considered.

619
00:46:11,362 --> 00:46:15,701
This is how I always look at it as in
boundary condition.

620
00:46:15,702 --> 00:46:20,039
So it's not that you need to resolve the
flow, you just

621
00:46:20,040 --> 00:46:24,378
need to provide the right boundary
condition to the part of your

622
00:46:24,379 --> 00:46:26,909
computational domain that is interesting
for you.

623
00:46:26,910 --> 00:46:31,247
However, if you are interested on the
exhaust, for example, that because

624
00:46:31,248 --> 00:46:35,224
what is at the, we still think of the jet
engine.

625
00:46:35,225 --> 00:46:39,563
So if at the exit of your combustor, you
have the turbine,

626
00:46:39,564 --> 00:46:44,916
You need the distribution of temperature
and velocity that is representative

627
00:46:44,917 --> 00:46:49,297
to the stage of the exit of the combustor.

628
00:46:49,298 --> 00:46:55,137
So you need to have a good
characterization of the flow that

629
00:46:55,138 --> 00:47:00,977
goes downstream. So in combustion in
general, people like me are not

630
00:47:00,978 --> 00:47:04,870
so much interested what happens downstream
the flame.

631
00:47:04,871 --> 00:47:06,817
So in that case,

632
00:47:06,818 --> 00:47:09,501
The experiments only measure at the flame
front.

633
00:47:09,502 --> 00:47:13,527
If we want to be predictive at capturing
the dynamics of the

634
00:47:13,528 --> 00:47:16,546
flame, we need to worry mainly about this
part.

635
00:47:16,547 --> 00:47:19,566
The walls can have an effect on the flame.

636
00:47:19,567 --> 00:47:23,592
Of course, can have. If you are not
resolving well the boundary

637
00:47:23,593 --> 00:47:27,618
layers, then of course you are going to
affect the circulation zones.

638
00:47:27,619 --> 00:47:31,644
So you need to have just a balance of how
much effort

639
00:47:31,645 --> 00:47:35,670
you want or resources you want to put or
points you want

640
00:47:36,005 --> 00:47:36,639
put.

641
00:47:36,640 --> 00:47:41,681
on each part. However, for other
applications in aerospace, in which you

642
00:47:41,682 --> 00:47:46,722
have a supersonic combustor, for example,
and then you have shock waves

643
00:47:46,723 --> 00:47:51,344
interacting with walls on those
conditions, then of course, solving the

644
00:47:51,345 --> 00:47:55,965
bounded layers is critically important.
Otherwise, the dynamics of the flow

645
00:47:55,966 --> 00:48:01,007
will not be predicted well. So it actually
depends on the kind

646
00:48:01,008 --> 00:48:03,948
of application that you are thinking of.

647
00:48:03,949 --> 00:48:11,253
Okay, so with everything you just said
about the complexities, know, in

648
00:48:11,254 --> 00:48:18,558
the, in other parts of the CFD world, GPUs
have been a

649
00:48:18,559 --> 00:48:22,211
pretty viable way of accelerating
simulations.

650
00:48:22,212 --> 00:48:26,472
And I always, I always prefer to

651
00:48:26,563 --> 00:48:30,634
talk about any HPC events, whether it's
CPUs or GPUs, is more

652
00:48:30,635 --> 00:48:34,704
that people can do more complex problems
rather than just, know, because

653
00:48:34,705 --> 00:48:38,775
I think most practitioners, yes, it's nice
that they can make their

654
00:48:38,776 --> 00:48:42,846
simulation faster, but then the next thing
they do is they go,

655
00:48:42,847 --> 00:48:46,238
right, now, how do I go to the next step?

656
00:48:46,239 --> 00:48:49,630
That, I think, has been largely proven to
be viable.

657
00:48:49,631 --> 00:48:53,613
for other things. But what about in
combustion?

658
00:48:53,614 --> 00:48:58,093
think when we've spoken, you've
highlighted that there's additional

659
00:48:58,094 --> 00:49:04,068
challenges. So my first question would be,
is moving to GPUs a

660
00:49:04,069 --> 00:49:10,042
kind of straightforward acceleration? And
how much does the hardware, in this

661
00:49:10,043 --> 00:49:16,016
case, let's say GPUs, make you reconsider
the choice of the algorithm

662
00:49:16,017 --> 00:49:19,501
and the solver from the ground up?

663
00:49:19,502 --> 00:49:24,448
Yes, that's a very cool question because
in my department and in

664
00:49:24,449 --> 00:49:29,396
my group we are dedicating a lot of effort
to this particular

665
00:49:29,397 --> 00:49:34,343
problem and I can tell you a little bit
what is my

666
00:49:34,344 --> 00:49:39,290
view on this. So indeed, you do things
when they are necessary,

667
00:49:39,291 --> 00:49:44,237
especially you have been working with your
code in a company or

668
00:49:44,238 --> 00:49:46,711
in a research lab like us.

669
00:49:46,712 --> 00:49:49,794
So you have developed your code for 20
years.

670
00:49:49,795 --> 00:49:53,220
Your code is very good. You can do many
things.

671
00:49:53,221 --> 00:49:57,331
You only want to improve models, Because
you have already prepared your

672
00:49:57,332 --> 00:50:01,442
code to accommodate all the
functionalities that you need, all the data

673
00:50:01,443 --> 00:50:03,840
structures in order to make it efficient.

674
00:50:03,841 --> 00:50:07,951
So that is fine. So the last thing that
you would like

675
00:50:07,952 --> 00:50:12,062
to do is to refactor the code from scratch
to reproduce the

676
00:50:12,063 --> 00:50:15,830
same things that you are reproducing. So
when that matters, well,

677
00:50:15,831 --> 00:50:21,103
In my opinion, it does matter when you see
that what I

678
00:50:21,104 --> 00:50:26,376
run with my code in 1000 cores, I can run
it with

679
00:50:26,377 --> 00:50:31,209
one GPU or 500 cores, I can run with one
GPU.

680
00:50:31,210 --> 00:50:36,482
And then the simulation that takes me one
day, I can do

681
00:50:36,483 --> 00:50:41,755
it in three hours in one GPU. So those
numbers are very

682
00:50:41,756 --> 00:50:43,073
intriguing. So then...

683
00:50:43,074 --> 00:50:47,035
you start becoming a little bit alert
about this, so cautious.

684
00:50:47,036 --> 00:50:47,536
So,

685
00:50:47,615 --> 00:50:52,092
okay, this is a game changer for us. So
then you talk

686
00:50:52,093 --> 00:50:56,195
to industry, they say, no, no, I'm happy
with my code.

687
00:50:56,196 --> 00:50:59,926
I I invested five, 10 years ago on my
cluster.

688
00:50:59,927 --> 00:51:04,403
I mean, I'm still taking use of it. I have
spent, I

689
00:51:04,404 --> 00:51:08,133
don't know, 50 years of CFD development in
my code.

690
00:51:08,134 --> 00:51:12,237
So GPU is not a problem to me. So this
is...

691
00:51:12,238 --> 00:51:19,660
2016, 2018, 2020. 2026 is like GPUs are
very powerful.

692
00:51:19,661 --> 00:51:27,161
You start seeing combustion codes running
on GPUs saying goodbye to the

693
00:51:28,568 --> 00:51:34,506
CPU codes, going Mac two across CPU codes.

694
00:51:34,507 --> 00:51:41,929
So now everyone is understanding that this
is a necessity.

695
00:51:42,079 --> 00:51:46,752
Also, from the whole infrastructure point
of view, if you need to

696
00:51:46,753 --> 00:51:51,426
buy a workstation or a cluster, then the
electricity bill always goes

697
00:51:51,427 --> 00:51:56,099
up. I don't know why, but this is
something for another discussion.

698
00:51:56,100 --> 00:52:00,772
You will never pay less for your
electricity bill in the future

699
00:52:00,773 --> 00:52:04,872
than what you pay now. It's always
increasing.

700
00:52:04,873 --> 00:52:10,510
So you can save some money by just running
on GPUs.

701
00:52:10,511 --> 00:52:12,860
because they are more energy efficient.

702
00:52:12,861 --> 00:52:17,561
So now this is where we are. So I think
this mindset

703
00:52:17,562 --> 00:52:22,261
is now changing. And now I think the
combustion community is starting

704
00:52:22,262 --> 00:52:26,178
to see or has started already a few years
ago.

705
00:52:26,179 --> 00:52:27,353
And now you

706
00:52:27,354 --> 00:52:33,363
see quite a lot of codes that are on
combustion running on

707
00:52:33,364 --> 00:52:39,373
GPUs. And when you look at those codes,
you should really, you

708
00:52:39,374 --> 00:52:40,375
should trade.

709
00:52:40,376 --> 00:52:45,359
take this with a lot of respect, whether
you like it or

710
00:52:45,360 --> 00:52:50,342
not, the numerics or what they do, because
the complexity is very

711
00:52:50,343 --> 00:52:55,326
high. I see a lot of codes for Navistokes
that can run

712
00:52:55,327 --> 00:53:00,309
on GPUs. They are very fast. But when you
want to add

713
00:53:00,310 --> 00:53:04,462
thermodynamics or thermochemistry in the
GPU, the dependency of specific

714
00:53:04,463 --> 00:53:09,446
enthalpies, properties that depend on
composition, and all that stuff that is

715
00:53:09,447 --> 00:53:09,862
usually

716
00:53:09,862 --> 00:53:14,847
done with libraries, then you don't need
to adapt your, you know,

717
00:53:14,848 --> 00:53:19,834
your gradient, you compute the divergence
or the, I don't know, the

718
00:53:19,835 --> 00:53:24,820
advection operator, the diffusion operator
is not only that, that is, I

719
00:53:24,821 --> 00:53:29,807
would say easy, you know, nowadays,
especially with the AI tools that

720
00:53:29,808 --> 00:53:33,962
help you with the loops and the pragmas
for GPUs.

721
00:53:33,963 --> 00:53:36,871
The problem is that your code relies

722
00:53:36,872 --> 00:53:40,621
on certain libraries for computing things,
chemistry, properties, et cetera,

723
00:53:40,622 --> 00:53:45,121
that you need to port those. And those are
usually old or

724
00:53:45,122 --> 00:53:49,621
usually are black box for some users. So
you need to open

725
00:53:49,622 --> 00:53:53,746
this black box and you need to work
directly with that.

726
00:53:53,747 --> 00:53:57,871
And that introduces delays and that also
introduces complexity and reduction

727
00:53:57,872 --> 00:54:01,996
of performance because you can say, no,
this is very difficult.

728
00:54:01,997 --> 00:54:04,621
I will do this in the CPU.

729
00:54:04,622 --> 00:54:09,716
And the rest I will do in the GPU, but
then you

730
00:54:09,717 --> 00:54:13,536
copy things across and then you pay the
price.

731
00:54:13,537 --> 00:54:18,631
So this is something that we initially
explored in one of the

732
00:54:18,632 --> 00:54:22,452
projects that I was coordinating that
ended in 2023.

733
00:54:22,453 --> 00:54:26,273
It was the European Center of Excellence
in Combustion.

734
00:54:26,274 --> 00:54:31,367
And then in this project, we had a list of
European partners

735
00:54:31,368 --> 00:54:33,490
that they developed CFD codes.

736
00:54:33,491 --> 00:54:38,298
for combustion and this was one of the
central topics of the

737
00:54:38,299 --> 00:54:43,105
discussion. How we can develop
functionalities in GPUs for our codes, how

738
00:54:43,106 --> 00:54:47,913
we can run hybrid CPU GPUs executions,
mainly because we cannot pour

739
00:54:47,914 --> 00:54:52,721
the whole code. Maybe we can pour the
chemistry to the GPU.

740
00:54:52,722 --> 00:54:57,529
If the chemistry is 70 % of my total cost
of the

741
00:54:57,530 --> 00:55:02,336
time step, if I accelerate the chemistry,
I will accelerate my code

742
00:55:02,337 --> 00:55:02,837
substantially.

743
00:55:02,859 --> 00:55:08,281
You do things part by part, but then you
realize that doing

744
00:55:08,282 --> 00:55:13,703
things part by part is very hard. Your
code is very large.

745
00:55:13,704 --> 00:55:19,125
You need to refactor many things. So many
people say, okay, stop

746
00:55:19,126 --> 00:55:21,836
refactoring. Let's a code from scratch.

747
00:55:21,837 --> 00:55:25,450
Native for GPU, the data structures are
ready.

748
00:55:25,451 --> 00:55:28,161
Everything will be designed. And then...

749
00:55:28,162 --> 00:55:33,161
This is really for me one of the
discussions that we are

750
00:55:33,162 --> 00:55:37,744
having. We have libraries for adaptive
refinement, for chemistry that are

751
00:55:37,745 --> 00:55:38,577
already available

752
00:55:38,578 --> 00:55:42,886
for GPU. Why don't we take them and we
build a main

753
00:55:42,887 --> 00:55:47,196
of our code with these libraries and then
we only need to

754
00:55:47,197 --> 00:55:51,505
do the PDEs. The PDEs at the end, this is
what we

755
00:55:51,506 --> 00:55:54,737
do. I mean, what we all have done. So.

756
00:55:55,352 --> 00:56:00,382
But the point I was trying to make is
today with coding

757
00:56:00,383 --> 00:56:05,413
agents, you know, from Mistral, OpenAI, or
Anthropic, you can write codes,

758
00:56:05,414 --> 00:56:06,251
right? That's...

759
00:56:06,252 --> 00:56:11,052
Now you can, you know, I think that whole
excuse of, it's

760
00:56:11,053 --> 00:56:15,853
hard for me to write the code or go to
rewrite it.

761
00:56:15,854 --> 00:56:20,654
I think actually these, this AI agents are
pretty good at writing

762
00:56:20,655 --> 00:56:25,456
codes, right? Do you think that is
actually now making this job

763
00:56:25,457 --> 00:56:27,456
a little bit more easier?

764
00:56:27,457 --> 00:56:33,235
Yes, that is exactly my point. you have to
reconsider to write

765
00:56:33,236 --> 00:56:38,051
the code because now you have a lot of
help.

766
00:56:38,052 --> 00:56:43,830
Before there was no help. So you could do
some scripts that

767
00:56:43,831 --> 00:56:49,610
substitute bloops. But now I think you can
really do a lot

768
00:56:49,611 --> 00:56:55,389
of things. What happens is again, this is
why combustion again is

769
00:56:55,390 --> 00:56:56,352
special because

770
00:56:56,353 --> 00:57:03,853
To get a combustion code working takes
time and people in academia

771
00:57:04,380 --> 00:57:08,394
mainly, yeah, they are rushing sometimes.

772
00:57:08,395 --> 00:57:09,063
Yes,

773
00:57:09,083 --> 00:57:14,020
so you take a code that works, it gives me
closer to

774
00:57:14,021 --> 00:57:18,957
the paper. But maybe for the long run,
investing on developing your

775
00:57:18,958 --> 00:57:23,894
own codes, maybe at low speed, it can give
you an advantage

776
00:57:23,895 --> 00:57:25,128
in the future.

777
00:57:25,129 --> 00:57:29,518
If you are able to manage well with these
agents and all

778
00:57:29,519 --> 00:57:33,908
these AI tools that are extremely helpful
for this, you just need

779
00:57:33,909 --> 00:57:38,298
to have very clear what you want. The
problem is that people

780
00:57:38,299 --> 00:57:42,687
don't have clear what they want. So when
they enter and interacting

781
00:57:42,688 --> 00:57:47,077
with this, then they get very lost
because, but if you know

782
00:57:47,078 --> 00:57:51,467
how your code should look like, because
you did it in the

783
00:57:51,468 --> 00:57:53,662
past for CPUs and you know,

784
00:57:53,663 --> 00:57:59,800
what works and what doesn't work, I mean,
I don't see that

785
00:57:59,801 --> 00:58:05,939
it will take that long. And yeah, I think
this is something

786
00:58:05,940 --> 00:58:10,031
that we will see more and more nowadays.

787
00:58:10,032 --> 00:58:16,169
I've seen in these journals that they give
you also like the

788
00:58:16,170 --> 00:58:21,796
GitLab for their computational models. You
can see that there are...

789
00:58:21,931 --> 00:58:26,671
more and more CFD codes that are just
created nowadays.

790
00:58:26,672 --> 00:58:32,359
And I think it's because of this. You can
really create things

791
00:58:32,360 --> 00:58:38,046
faster. The problem of combustion is again
that you need a lot

792
00:58:38,047 --> 00:58:42,312
of dependency and you need a lot of
thermodynamics.

793
00:58:42,313 --> 00:58:47,526
So CP is not constant. And then gamma is
not constant.

794
00:58:47,527 --> 00:58:48,948
Then this is...

795
00:58:48,949 --> 00:58:53,085
I mean, people working in combustion will
understand very well what I

796
00:58:53,086 --> 00:58:55,498
mean, because making all those quantities
temperature-dependent,

797
00:58:55,499 --> 00:58:58,601
composition-dependent creates a lot of
dependencies in the code.

798
00:58:58,602 --> 00:59:02,738
But I think this should not stop people
developing their codes and

799
00:59:02,739 --> 00:59:06,530
learning from this, because you really
learn a lot of things.

800
00:59:06,531 --> 00:59:10,667
Maybe you don't get your paper that fast,
but maybe you can

801
00:59:10,668 --> 00:59:12,736
get more papers in the future.

802
00:59:12,737 --> 00:59:17,997
Yeah, so maybe a final question for you,
which is more of

803
00:59:17,998 --> 00:59:23,258
a slightly forward looking question a
little bit, but also now is

804
00:59:23,259 --> 00:59:28,519
AI. So we just talked about agents. So
leaving that aside, maybe

805
00:59:28,520 --> 00:59:33,780
in the aerospace and automotive world,
when it comes to external aerodynamic

806
00:59:33,781 --> 00:59:38,164
surrogate models have become, you know, a
really hot topic.

807
00:59:38,165 --> 00:59:39,918
And, and there's been

808
00:59:39,919 --> 00:59:44,449
you know, I would say reasonably good
proof that they are getting

809
00:59:44,450 --> 00:59:48,980
much closer now to being a sort of
technology readiness level to

810
00:59:48,981 --> 00:59:53,512
give a legitimate tool for people to use
within the design process,

811
00:59:53,513 --> 00:59:58,043
not a replacement to, you know,
traditional sort of PDE solvers, but

812
00:59:58,044 --> 01:00:02,574
certainly something, you know, that can
help, particularly as a designer, you

813
01:00:02,575 --> 01:00:07,105
say, know, it's shifting through. Where do
you see that, you know,

814
01:00:07,106 --> 01:00:10,126
sort of surrogate modeling technology in
the combustion?

815
01:00:10,127 --> 01:00:17,530
If that's something that is being tested,
embraced, rejected, where's your

816
01:00:17,531 --> 01:00:20,222
community seeing those approaches?

817
01:00:20,223 --> 01:00:27,004
Yes, I would say it has been quite a big
acceleration

818
01:00:27,005 --> 01:00:32,557
of the development of these of surrogate
models for combustion systems.

819
01:00:32,558 --> 01:00:38,615
I think over the last, I mean it started
many years ago,

820
01:00:38,616 --> 01:00:44,673
but it has been especially growing over
the last five to six

821
01:00:44,674 --> 01:00:50,731
years. So I think they are going to have a
play, they

822
01:00:50,732 --> 01:00:53,760
are going to have a role.

823
01:00:53,761 --> 01:00:59,740
However, what I see a bit less is how
these tools are

824
01:00:59,741 --> 01:01:05,719
currently integrated into the design.
there has been, what I see is

825
01:01:05,720 --> 01:01:11,699
that there is a lot of research on this,
which has, which

826
01:01:11,700 --> 01:01:17,678
I see is ending at the research level and
not being taken

827
01:01:17,679 --> 01:01:23,658
yet by the industry. So I think this is
more or less

828
01:01:23,659 --> 01:01:27,671
this threshold situation that I see, there
will be a moment, and

829
01:01:27,672 --> 01:01:31,014
I think this happens in all areas of the
technology.

830
01:01:31,015 --> 01:01:35,027
So you accumulate knowledge and confidence
in something, and then suddenly you

831
01:01:35,028 --> 01:01:39,040
start integrating things. You don't
integrate things that are very new, and

832
01:01:39,041 --> 01:01:43,052
people are a bit skeptical about them,
especially companies that, you know,

833
01:01:43,053 --> 01:01:45,727
if everything works, I don't touch it, no?

834
01:01:45,728 --> 01:01:48,068
I think this is more or less...

835
01:01:48,180 --> 01:01:52,603
What I see, most of the companies have
their thinking, of course,

836
01:01:52,604 --> 01:01:57,027
they think for future, but if something is
working, you can do

837
01:01:57,028 --> 01:02:01,450
research, you can be ready to change it,
but don't change it

838
01:02:01,451 --> 01:02:01,820
yet.

839
01:02:01,820 --> 01:02:08,613
And I believe that over the next years, we
will start seeing

840
01:02:08,614 --> 01:02:14,275
this because the companies have started
integrating these digital workflows

841
01:02:14,276 --> 01:02:21,069
more into their systems. they initially
relied on control systems or design

842
01:02:21,070 --> 01:02:27,297
systems, very guided by specific companies
that they develop a specific

843
01:02:27,298 --> 01:02:28,996
software. And now...

844
01:02:29,184 --> 01:02:33,266
this has opened up substantially with the
AI tools.

845
01:02:33,267 --> 01:02:38,709
And now you don't really need to buy a
specific software to

846
01:02:38,710 --> 01:02:44,152
do an optimization. You can do that with
AI in a Python

847
01:02:44,153 --> 01:02:49,555
Jupyter Notebook nowadays, connected to a
cluster that has some execution.

848
01:02:50,035 --> 01:02:52,460
So it's a matter of time.

849
01:02:52,461 --> 01:02:56,995
I've been, in fact, just to be very
precise, mean, I've been

850
01:02:56,996 --> 01:03:01,530
in a conference back in Italy, European,
Italian, and Spanish sections, and

851
01:03:01,531 --> 01:03:05,687
there were some companies that
participated in this discussion, and this

852
01:03:05,688 --> 01:03:10,222
question was answered. very, I mean, there
were some companies that were

853
01:03:10,223 --> 01:03:13,624
saying, yes, we recognize that these tools
are available.

854
01:03:13,625 --> 01:03:18,159
We are at the process of integrating them
or thinking about how

855
01:03:18,160 --> 01:03:21,938
to integrate in them. they were companies
were saying, no.

856
01:03:21,939 --> 01:03:25,045
I don't see the value.

857
01:03:25,233 --> 01:03:31,560
I could also see something which is also
related to generations.

858
01:03:31,561 --> 01:03:37,888
I think the new generations are accepting
this digitalization and integrating

859
01:03:37,889 --> 01:03:43,065
the digitalization as part of their basis
in the...

860
01:03:43,187 --> 01:03:45,739
I don't know, in their life, in their
normal life, but

861
01:03:45,740 --> 01:03:52,806
also in the work environment. So in the
past, doing something with

862
01:03:52,807 --> 01:03:56,929
computers, they call you informatics. And
I

863
01:03:56,930 --> 01:04:00,278
don't know anything about informatics. No,
no, no, I switch on the

864
01:04:00,279 --> 01:04:01,673
computer and I click the

865
01:04:01,674 --> 01:04:06,856
button. And that is a mindset that...

866
01:04:06,857 --> 01:04:12,641
it is changing dramatically nowadays
because everyone is has in the phone,

867
01:04:12,642 --> 01:04:15,533
ChatGPT or whatever of these things.

868
01:04:15,813 --> 01:04:20,829
And now, you know, they are going to start
relying more in

869
01:04:20,830 --> 01:04:25,845
these things as soon as they become, they
can see them more

870
01:04:25,846 --> 01:04:28,771
available in other aspects of their life.

871
01:04:28,772 --> 01:04:33,787
And one of the things, in my opinion, that
could be limiting

872
01:04:33,788 --> 01:04:36,713
is that when you pay for something,

873
01:04:36,714 --> 01:04:40,475
you have a guarantee that something is
working.

874
01:04:40,476 --> 01:04:45,647
And this is something that we don't have
the maturity today.

875
01:04:45,648 --> 01:04:51,289
In, I said this, it will give me trouble
if somebody reads

876
01:04:51,290 --> 01:04:56,932
this, in CFD codes, in academic CFD codes,
we're working extremely hard

877
01:04:56,933 --> 01:05:02,574
on this. All people like us, like me and
the people I

878
01:05:02,575 --> 01:05:04,925
work with developing codes, we...

879
01:05:05,065 --> 01:05:10,984
put so much effort on this aspect and
until we reach certain

880
01:05:10,985 --> 01:05:16,410
maturity that people paying a license for
another commercial software might

881
01:05:16,411 --> 01:05:20,355
think their software is more reliable than
us.

882
01:05:20,356 --> 01:05:26,274
So I think in terms of digitalization, let
me call it that

883
01:05:26,275 --> 01:05:32,193
way, people still think that they're
paying a license, they give you

884
01:05:32,194 --> 01:05:33,673
more efficient and...

885
01:05:33,674 --> 01:05:37,734
more reliable tools for their design
activities or their engineering

886
01:05:37,735 --> 01:05:41,796
activities. But they will realize in few
years, they're not.

887
01:05:41,797 --> 01:05:46,669
This is not the case because you can build
your own models,

888
01:05:46,670 --> 01:05:49,512
you can build your own tests, and

889
01:05:49,513 --> 01:05:54,612
it's not that difficult because you have
all the surroundings around.

890
01:05:54,613 --> 01:05:59,249
Research centers, you have AI tools,
everything is open source.

891
01:05:59,250 --> 01:06:01,567
It's an open source environment.

892
01:06:01,568 --> 01:06:06,495
But it's also, I can understand that it's
also overwhelming for some

893
01:06:06,496 --> 01:06:09,780
people to get into this because it's
endless.

894
01:06:10,908 --> 01:06:14,424
Cool, thanks Danny. Really appreciate
taking the time to chat.

895
01:06:14,425 --> 01:06:18,644
I learned a lot actually all about the
hydrogen and the aircraft

896
01:06:18,645 --> 01:06:22,864
industry and combustion. yeah, look
forward to catching up in person soon.

897
01:06:22,865 --> 01:06:25,384
Thank you, Anil. Thank you. It was my
pleasure.