应机械结构强度与振动国家重点实验室、智能飞行器流固耦合力学与仿生技术学科创新引智和陕西省先进飞行器服役环境与控制重点实验室邀请，韩国科学院、工程院两院院士、JFM副主编、韩国首尔大学HAECHEON CHOI教授，将于近期访问西安交通大学航天航空学院并作学术报告。欢迎大家参加。

时 间： 2018年10月15日下午14:30-16:00

地 点： 航天航空学院教一楼第三会议室

报告人：Prof.Haecheon Choi

报告题目: Machine-learning based turbulence prediction and control

摘要：An  accurate but efficient prediction of turbulence is one of the ultimate  goals in fluid mechanics society. To predict turbulence, it is important  to know the correlations among two or more flow variables at different  spatial locations. Understanding these correlations from the  Navier-Stokes equations is quite difficult and sometimes impossible. In  this talk, we apply machine learning (ML) tools (from linear regression  to deep learning) to predict turbulence for two different problems: one  is to model subgrid-scale (SGS) stresses for large eddy simulation, and  the other is to predict near-wall turbulence based on wall variable  sensing. For SGS modeling, we first train the ML model for homogeneous  isotropic turbulence to predict SGS stresses from resolved flow  variables. Results show that the ML model outperforms traditional models  such as the Smagorinsky model for the predictions of SGS dissipation,  energy spectrum, and vortical structures. We also train ML models for  turbulent channel flow to predict near-wall flow based on wall variable  sensing. The near-wall flows predicted are very similar to real ones.  How to visualize (or understand) the ‘black box’ in the process of ML is  also discussed in this talk. Finally, turbulence control based on wall  variable sensing is performed for skin friction reduction in channel  flow, providing a significant amount of drag reduction.

报告人简介：

Professor  Choi received his BS and MS degrees from Seoul National University in  1985 and 1987, respectively, and his Ph.D degree from Stanford  University in 1992. He has been a professor at Seoul National University  since 1993. He is interested in turbulence, flow control, CFD, and  bio-mimetic engineering. He is a fellow of American Physical Society,  and a member of The National Academy of Engineering of Korea and The  Korean Academy of Science and Technology. He is an Associate Editor of  Journal of Fluid Mechanics, and editorial board member for Flow,  Turbulence and Combustion, Int. J. Heat and Fluid Flow, and Int. J.  Multiphase Flow.