Chapter 946 Chang’s Turbulence


    ??The numerical calculation business department headed by Liu Hongbo and the technical department headed by Wei Yongming are two parallel departments that are not subordinate to each other.


    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 TORC 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 Technology Department.


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


    ? Many small companies, or ordinary universities, saw that Torch Group provided this kind of service, and simply gave up their plans to start simulations from scratch and directly outsourced all related business.


    ?At first, Chang Haonan felt that this was a bit of a delay, so he set a rule to give priority to those users who purchased TORCH Multiphysics.


    However, the business volume has not decreased at all.


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


    Later, they were even able to overtake the profits of the software division from time to time.


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


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


    Logically speaking, for this type of high-impact project, for the sake of safety, you should choose the most proficient computing tool possible, that is, an old version with stable performance.


    But right now, Dassault is pressing too hard.


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


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


    …


    Soon, about a dozen business backbones were pulled into an office on the top floor of Torch Group.


    Chang Haonan was already sitting at the head of the conference table, waiting for everyone.


    In fact, after serving as the chief planner of the Aviation Power Group and a professor at Beijing Hang University, he rarely returned to the Torch Group to work.


    Hence, some new employees may not even have met Chang Haonan himself.


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


    Liu Hongbo arranged the seats for the rest of the people, and then he sat on the left hand side closest to Chang Haonan:


    "Mr. Chang, according to your request, these comrades have either participated in the Ice Flying Group''s helicopter project with me, or they have switched jobs from the Aviation Industry Corporation of China, and they all have aircraft-related design experience. …”


    When the Numerical Computing Business Department was expanded a few years ago, there were still relatively few people who were proficient in this skill throughout China.


    ??Moreover, a considerable number of them are the "disciples" brought out by Chang Haonan in the aviation industry system.


    For example, Lin Shikuan and others from Institute 601.


    ?At that time, Torch Group happened to be named and praised by superiors as a model of "high-tech enterprise".


    Therefore, in order to show support for Chang Haonan and to solve the work problems of some non-staff personnel after the reduction of state-owned enterprise staff, the two parties hit it off and transferred the working 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 parties 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 "enemies".


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


    Otherwise it would just depend on him and Liu Hongbo...


    I’m exhausted and can’t keep up with the deadline.


    “Comrades, I now have a calculation application submitted by the French Dassault Group, which is the airfoil design of a high-speed business jet...”


    “...” ????After everyone sat down, Chang Haonan first introduced the general situation of this project in a few words as quickly as possible.


    Immediately afterwards, the topic shifted to today’s focus:


    “This task has a tight deadline and heavy tasks. The fault tolerance rate based on the current old version of TORC Multiphysics algorithm is quite low, and there are no opportunities for trial and error at all, so some new computing tools are needed to improve efficiency.”


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


    “Fortunately, one of the optimizations related to CFD has been completed and can be applied in the current 1.32 version of the software in the form of a custom function module…”


    …”


    TORCHMultiphysics is welcomed by 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 by themselves and integrate them into the software.


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


    …


    Almost all the people sitting in this conference room have worked in the same R&D team as Chang Haonan in the past.


    So, when he heard that there was a new optimization, everyone took out their notebooks as if they were conditioned reflexes——


    too familiar.


    It seems like we are back to the days when we worked on projects together in the past.


    Chang Haonan, who saw this scene, also smiled knowingly.


    Then he put down the tea cup, just like before, got up and walked to a mobile blackboard:


    “Simply put, turbulence problems are still the main factor restricting engineering fluid simulation at present, and after taking into account efficiency and accuracy requirements, the currently widely used method is still dominated by the Reynolds average equation.”


    “But for complex engineering fluid motions, 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 simulations.”


    “Therefore, I made some improvements to the two-equation model commonly used in the past. Only the turbulent kinetic energy is transported, and other turbulent variables are solved algebraically using high-order dimensionality reduction methods..."


    At this time, someone from below suddenly interjected in a low voice:


    “The new turbulence model... why not just call it Chang’s turbulence?”


    ??The half-joking tone triggered a burst of good-natured laughter, which was just the right amount to relieve the somewhat tense atmosphere in the conference room.


    Amid the laughter and laughter, more than one person actually wrote "Chang''s Turbulence" as a name in his notebook...


    While talking and laughing, Chang Haonan had already written the N-S equation on the blackboard that everyone is familiar with.


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


    ? 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 requires additional processing methods for the density changes of the grid, which is not suitable for direct programming calculations. Therefore, the physical space (x, y, z, t ) into the computational space (ξ, η, ζ, τ)..."


    "From the closedness problems of turbulence simulation that we have often solved in the past, we can find that the solution and determination of the mixing length need to be linked to the turbulence field boundary conditions and flow conditions. There is no universal equation. In order to solve this problem, I will use the method of seeking the mixing length distribution of spatial turbulent structures to establish a universal connection between Reynolds stress and time-averaged flow field..."


    …”


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


    Especially at the level of mathematical theory.


    Fortunately, others have not been idle over the years.


    The accumulation of a large amount of computing experience has somewhat enhanced their understanding of computing models and algorithms.


    Therefore, although we cannot fully understand all the theoretical knowledge used by Chang Haonan, at least everyone can still keep up with the ideas.


    Compared to the situation in the past when I would be interrupted and asked questions every time I spoke, it has improved a lot.


    This is the most precious wealth that Chang Haonan has left since his rebirth...


    (End of this chapter)