Chapter 946 Chang's Turbulence

The numerical calculation business department headed by Liu Hongbo and the technical department headed by Wei Yongming are two independent and equal departments.

In fact, Chang Haonan first decided to let Torch Group take over part of the numerical calculation business. The original intention was to provide after-sales service to TORCH Multiphysics users who had needs for numerical calculations but did not have sufficient capabilities.

From this perspective, he once considered setting up the Numerical Computing Business Department as a second-level department under the Technical Department.

But before he could finalize the matter, this business, which was originally just a supporting business, became a new hot spot.

Seeing that Torch Group provides this kind of service, many small companies or general universities simply gave up their plans to start simulation from scratch and directly outsourced all related businesses.

At first, Chang Haonan felt that this would be a bit of a waste of time, so he set a rule to give priority to those users who had purchased TORCH Multiphysics.

However, the volume of business has not decreased at all.

In the end, there was no choice but to continuously expand the scale of the numerical calculation business department and then officially list it as one of the company's main businesses.

Later, they were even able to surpass the software division's profits from time to time.

Therefore, although there is cooperation between the two, most of the time they are still responsible for their own little piece of land.

As for the "secret trump card", since it was prepared for the 2.0 version of TORCH Multiphysics, and Liu Hongbo had not used it yet, he naturally knew nothing about it.

Logically speaking, for projects with such a large impact, for the sake of safety, one should choose the most proficient computing tools possible, that is, old versions with stable performance to complete them.

But right now, Dassault is pushing us too hard.

In addition, from what Chang Haonan said, this trump card was developed by him himself.

Then, Liu Hongbo is also willing to give it a try...

……

Soon, about a dozen key business personnel were brought to an office on the top floor of Torch Group.

Chang Haonan had already sat at the head of the conference table, waiting for everyone.

In fact, after serving as the chief planner of Aviation Power Corporation of China and professor of Beijing University of Aeronautics and Astronautics, he rarely returned to Torch Group to work.

Therefore, some new employees may not even have met Chang Haonan in person.

Fortunately, the people who just walked in looked familiar. They should be the earliest members of Torch Group.

Liu Hongbo arranged seats for the other people, and then sat down on the left side, closest to Chang Haonan:

"Boss Chang, according to your request, these comrades have either worked with me on the helicopter project of Bingfei Group, or have jumped from the Aviation Industry Corporation of China. They all have experience in aircraft design..."

When we expanded the numerical computing business department a few years ago, there were relatively few people in the whole of China who could master this skill.

Moreover, a considerable number of them are Chang Haonan’s “apprentices” in the aviation industry system.

For example, Lin Shikuan and others from Institute 601.

During that period, Torch Group happened to be singled out by its superiors as a typical "high-tech enterprise" and praised by them.

Therefore, in order to show support for Chang Haonan and to solve the work problems of some non-staff personnel after the reduction of the establishment of state-owned enterprises, the two parties hit it off and transferred the work relationship of some of them to Torch Group.

At that time, the latter was still an enterprise under the Academy of Sciences system, and both sides were happy.

Who would have thought that within two years, Torch Group would become a wholly-owned subsidiary of Aviation Power Group...

Now it becomes "aiding the enemy".

However, it was precisely because of these people that Chang Haonan had the confidence to take on the wing design task alone two days ago.

Otherwise, relying on him and Liu Hongbo alone...

You can't catch up with the deadline even if you work yourself to death.

"Comrades, I have a calculation application submitted by the French Dassault Group. It is a wing design for a high-speed business jet..."

"..."

After everyone was seated, Chang Haonan first introduced the general situation of the project in a few words as quickly as possible.

Then, the topic shifted to today's focus:

"This is a time-sensitive and demanding job. The old version of TORCH Multiphysics has a very low error tolerance rate and there is no chance for trial and error. So we need some new computing tools to improve efficiency."

"Originally, the new software version 2.0 was optimized for this kind of external flow field simulation calculation task, but the software itself has not been tested and packaged yet, so it cannot be used directly."

"Fortunately, an optimization related to CFD has been completed and can be applied in the current version 1.32 of the software in the form of a custom function module..."

"..."

TORCH Multiphysics is popular among many top research institutions. In addition to its excellent performance, this highly free custom module is also a major reason.

It allows advanced users to edit models or algorithms themselves and integrate them into the software.

Although there are still some limitations, for the software industry in 1997, it was almost like unlimited imagination.

……

Almost everyone sitting in this conference room had worked in the same R&D team as Chang Haonan in the past.

So, when he mentioned a new optimization, everyone took out their notebooks as if by reflex.

too familiar.

It's like going back to the days when we worked on projects together.

Chang Haonan, who saw this scene, smiled knowingly.

Then he put down his teacup, and just like before, he stood up and walked to a mobile blackboard:

"In short, turbulence is still the main factor restricting engineering fluid simulation. After taking into account the requirements of efficiency and accuracy, the widely used method is still mainly based on the Reynolds average equation."

"But for complex engineering fluid motion, such as flow separation and transition prediction, a turbulence model that takes into account different flow states is needed, which will inevitably greatly improve the efficiency and accuracy of engineering fluid simulation."

"Therefore, I made some improvements to the two-equation model that was commonly used in the past. I only transported the turbulent kinetic energy, and used a high-order dimensionality reduction method to algebraically solve other turbulent variables..."

At this time, someone suddenly interrupted quietly:

"The new turbulence model... why not just call it Chang's turbulence?"

The half-joking tone triggered a good-natured laugh and just enough to ease the somewhat tense atmosphere in the meeting room.

Amidst the laughter and joy, more than one person actually wrote "Chang's Turbulence" as the name in their notebooks...

While chatting and laughing, Chang Haonan had already written the NS equation that everyone is familiar with on the blackboard.

Of course, for the speed range of the Falcon Z project, there is no need to consider body forces and additional heating.

Q/t+(F-Fv)/x+(G-Gv)/y+(H-Hv)/z=0.

"The Cartesian coordinate system directly coincides with the physical position of the computational domain, but additional processing methods are required for the density change of the grid, which is not suitable for direct programming calculations. Therefore, it is necessary to first convert the physical space (x, y, z, t) into the computational space (ξ, h, z, t)..."

"From the closure problems of turbulence simulation that we have often solved in the past, we can find that the solution and determination of the mixing length needs to be linked to the boundary conditions and flow conditions of the turbulent field, and there is no universal equation. In order to solve this problem, I will seek the mixing length distribution of the spatial turbulence structure as a means to establish a universal connection between the Reynolds stress and the time-averaged flow field..."

"..."

The difficulty of the content introduced by Chang Haonan has made a qualitative leap compared to the original one.

Especially at the level of mathematical theory.

Fortunately, other people have not been idle over the years.

The accumulation of a large amount of computing experience has also enhanced their understanding of computing models and algorithms to some extent.

Therefore, although we could not fully understand all the theoretical knowledge used by Chang Haonan, at least everyone could follow his ideas.

Compared to the situation in the past where people would interrupt me and ask questions every time I spoke, it is much better now.

And this is the most precious treasure that Chang Haonan has left behind since his rebirth...