Chapter 941: Battle of Wits and Courage with the Air
Of course, the term "backstabbing" is just Chang Haonan's inner complaint.
If he really said it out loud, it would be a bit of an exaggeration.
Although Dassault has cooperated with Torch Group, it is also one of the important users of TORCH Multiphysics software, and even purchased a supercomputer specially launched by Sugon Group.
But in the field of numerical calculation, it is always just a relationship between manufacturers and customers.
The two parties have not formed any form of business alliance, and the cooperative research and development agreement of Falcon Z does not stipulate in what form the engineering files must be submitted.
However, this kind of "partner abandons himself and chooses similar products from friendly companies" is really too NTR.
Therefore, Chang Haonan still downloaded the engineering file.
In fact, after a certain minor version of TORCH Multiphysics, it can even be compatible with opening and editing cmph files.
At most, some exclusive functions of COMSOL Multiphysics will not be available.
Soon, a wing that has been meshed appeared on Chang Haonan's computer screen.
Moreover, it is already detailed.
If you zoom in, you can even see the flaperon modeling and winglets.
Strictly speaking, it is a wingtip sail.
It should be based on some designs of the Airbus A320.
Of course, this is normal.
Aircraft design, especially civil aircraft design.
Useful elements will soon spread from one person to ten, from ten to a hundred.
"Let me see what you are calculating..."
Chang Haonan began to further check some of the data in the engineering files-
When the first trial version of 1ultiphysics was released, the commonly used and convenient storage media was almost only 3.5-inch floppy disks.
In order to avoid the situation where the engineering files are too large and need to be stored on several disks, Chang Haonan separated the edited and run log files from the engineering files.
Later, this became a common practice for almost all numerical calculation software.
As a result, the boomerang now hits his head.
In the absence of information, Chang Haonan spent about half an hour to figure out what problems the Dassault engineers were studying.
In short, they should be preparing to design a wing with extremely low drag in the transonic range.
Since the low-thrust turbofan modified from the M88 core engine is powerful, as long as the resistance of the fuselage, especially the wing part, meets the standard, the aircraft can achieve economical and quiet navigation at the "quasi-sonic speed" of 0.9 Mach or even 0.95 Mach.
This means that compared with competitors on the market whose speed is generally 0.7-0.8 Mach, the Falcon Z can save about 15% of flight time.
For the customer group targeted by business jets, it is obviously very attractive.
And it is also a very good publicity gimmick.
However, it is impossible for the Falcon Z to make the wing into a delta wing or a swept wing.
To achieve excellent near-sonic performance on a wing that is generally a straight wing, it is hopeless to just optimize the airfoil.
The details of the wing surface must also be paid attention to.
And this engineering document is to calculate the air flow near the wing surface.
It is similar to the nature of the work done by Chang Haonan when he optimized the J-8C wing shape.
But the level of sophistication is much higher.
After all, within the permitted range of the structure, fighter jets do not need to consider the noise and vibration caused by airflow.
In fact, even if only the structure is considered, a straight wing with a large aspect ratio is much more complicated than a delta wing.
Therefore, judging from the content presented in this engineering document, Dassault engineers seem to be still in a relatively early stage of research.
And the switch to COMSOL Multiphysics is probably due to its high computational efficiency in its publicity.
Otherwise, this wing profile is likely to not catch up with the schedule of the Falcon Z.
Of course, passenger aircraft have relatively simple structures.
Many models (such as the Xianzhou 60 of that year) even provide customers with wings of different designs as optional parts.
But if it can catch up with the first launch as standard, it will definitely be better.
However...
Looking at the wing modeling on the screen, Chang Haonan gently put his hand on his chin.
"This calculation result seems... There are some problems?"
Before Samsung Marine Engineering made this wave of things, Chang Haonan had been studying the solution to the problem of high computational weight when solving the viscoelastic constitutive equation using the finite volume method out of interest.
In fact, he has found a constitutive equation that does not involve diffusion terms, but he has not yet found a specific solution.
In that process, Chang Haonan used a large number of existing examples at hand to provide "learning materials" for the high-order data dimensionality reduction process.
Therefore, although he himself cannot give numerical calculation results accurate to a certain number of digits like a computer, he still has some intuition about the characteristics, or trends, of the results.
But the several sets of results calculated by Dassault did not conform to his intuition.
"Professor Liu."
Chang Haonan raised his head and looked at Liu Hongbo, who was sitting on the sofa and had drunk who knows how many cups of tea.
"Hmm?"
The latter was bored and struggling whether to take the initiative to say goodbye, when he heard the voice of his boss:
"Mr. Chang, you say."
"You have version 2.5 of COMSOL Multiphysics, right?"
Chang Haonan asked.
"some."
Liu Hongbo answered with some confusion.
"That's good."
Chang Haonan said, returning his gaze to the screen, and then forwarded the email from Dassault to Liu Hongbo's mailbox:
"I sent you an email containing a COMSOL Multiphysics project file. When you go back, open it with their latest version of the software. Don't change anything and just start the calculation from scratch."
Although Liu Hongbo still didn't know what Chang Haonan wanted to do, he still nodded:
"Okay, I'll send you the results as soon as possible."
However, Chang Haonan shook his head directly:
"No...it turns out I don't need it."
"When the time comes, you can extract the log of this calculation process and send it to my email."
…
Liu Hongbo's movements were quite fast.
Less than two days later, Chang Haonan received the log file he sent.
txt format.
COMSOL Multiphysics was released independently several years earlier than in history, so many software-level details are not good.
For example, typically, logs are stored directly in txt format.
Of course, for a hardcore person like Chang Haonan who checks logs with naked eyes, this is indeed a lot more convenient.
And the results of the inspection...
It also confirmed his guess two days ago.
"It's really fucked..."
Chang Haonan leaned back in his chair and laughed and cursed to himself——
Since nearly two months ago, he began to think about how COMSOL would solve the high computational weight problem of viscoelastic constitutive equations.
And the result is...
Not solved at all...
It can be seen from the log that the calculation process is to directly solve the N-S equation numerically using the grid-centered FVM discretization method according to the general method.
However, situations with these characteristics are indeed quite extreme and are not actually common.
In particular, COMSOL’s past regular customers were generally schools and small and medium-sized enterprises with limited strength and financial resources.
Even less common.
Most of the new customers who started trying to use COMSOL Multiphysics after version 2.5 have not yet fully adapted to it.
Just like Dassault, they have already started using it to start projects, but they are still in a state of exploration.
I don't even know if there is a problem with the results.
So, so far, the Swedes should not have received relevant feedback.
In other words, they probably didn’t know or thought about the problem from beginning to end...
And Chang Haonan...
He has been battling with the air.
Thinking of this, he shook his head with a wry smile, then opened a Word document and prepared to write a memo to inform Dassault of the situation.
After all, Falcon Z is a joint development project.
If something goes wrong in a big job like the wing, it will inevitably affect the progress of the entire project.
By the way, we can legitimately let them use the computing tools of the past.
Thanks to the fact that the finite volume method is not bound, TORCH Multiphysics does not need to face the problem of high calculation weight when calculating the viscoelastic constitutive equation.
The price is that it consumes more computing resources.
But no matter what, it's better than figuring out the problem in the end.
As for the competitor COMSOL...
Chang Haonan already had a rather "evil" idea.