Speaker：Yue Yang (Peking University)

Chair Person: Wei Kang (Distinguished research fellow)

Date：October 28, 12:30-13:30

Place：Room 210 COE Building No.1

Report Introduction:

We present a Lagrangian study on the evolution of turbulent coherent structures in the laminar-turbulent transition in incompressible channel flow and weakly compressible boundary layer flow. Based on the Eulerian velocity field from the direct numerical simulation, a backward-particle-tracking method is used to solve the Lagrangian scalar transport equation, and then Lagrangian material surfaces are extracted as isosurfaces of the Lagrangian scalar. As an approximation of the Helmholtz vorticity theorem, a Lagrangian surface, which is initially a vortex surface composed of vortex lines, can be approximately considered as a vortex surface before significant vortex reconnections in temporal evolution. By tracking the evolution of Lagrangian material surfaces in the early transitional phase, the dynamics of coherent structures, e.g., hairpin vortices, can be studied in a Lagrangian framework. The statistical geometry of Lagrangian structures can then be quantified by scalar gradients and the multi-scale, multi-directional geometric analysis.
 

About Speaker:
　　Yue Yang received double BE degrees in Thermal Engineering and Computer Science from Zhejiang University in 2004, MS degree in Fluid mechanics from Institute of Mechanics, Chinese Academy of Sciences in 2007, and PhD degree in Aeronautics from California Institute of Technology in 2011. Sponsored by the Combustion Energy Research Fellowship from CEFRC, Princeton University, Yang’s postdoc research was on advanced simulations of turbulent combustion at Cornell University and Sandia National Laboratories. Yang joined the Department of Mechanics and Engineering Science in College of Engineering, Peking University in 2013. His current research interests include modeling and numerical simulation of turbulence, turbulent combustion, and vortex dynamics.