1. 제 목 : Effects of High Mach Number on Turbulent Boundary Layers

2. 연 사 : Prof. John Kim (Department of Mechanical and Aerospace Engineering, UCLA)

3. 일 시 : 2013년 6월 7일 (금) 16:30-17:30

4. 장 소 : 301동 105호

5. 내 용
Compressible turbulent boundary layers with free-stream Mach number ranging from 2.5 up to 20 were analyzed by means of direct numerical simulation of the Navier-Stokes equations. For the present study the fluid was assumed to be an ideal gas with constant specific heats. A hybrid numerical scheme, which can capture shocks and shocklets and yet accurately compute turbulent motions in smooth regions was used for simulation of spatially developing compressible turbulent boundary layers. The main objective of this study was to investigate the effects of high Mach number on turbulence statistics and near-wall turbulence structures. It was shown that supersonic/hypersonic boundary layers at zero pressure gradient exhibited close similarities to incompressible boundary layers, and that the main turbulence statistics could be correctly described as variable-density extensions of incompressible results. The probability density function of the velocity dilatation showed significant variations as the Mach number was increased, but it could also be normalized by accounting for the variable-density effect. The compressible boundary layer also showed a similarity to the incompressible boundary layer in the sense that, without the linear coupling term, near-wall turbulence could not be sustained.

6. 약 력
John Kim is Rockwell Collins Distinguished Professor in Department of Mechanical and Aerospace Engineering at UCLA. He received his Ph.D. in Mechanical Engineering from Stanford University in 1978. Prior to joining UCLA he was with NASA Ames Research Center, where he conducted research in the areas of turbulence and transition physics as a research scientist and Chief of Turbulence and Transition Physics Branch. John Kim’s primary research interest is numerical simulation of transitional and turbulent flows, physics and control of turbulent flows, and numerical algorithms for computational science. John Kim has been a pioneer in developing direct numerical simulations (DNS) and large eddy simulations (LES) as a reliable and respected tool for studying physics of turbulence. His current interest includes applying systems control theoretic approach to turbulence control and turbulent physics in hypersonic turbulent boundary layers. John Kim received NASA Medal for Exceptional Scientific Achievement in 1985, Otto Laporte Award from the American Physical Society in 2001, Ho-Am Prize in Engineering from the Ho-Am Foundation in 2002, Distinguished Alumni Award from College of Engineering, Seoul National University in 2009. He is a Fellow of American Physical Society and a member of the U.S. National Academy of Engineering. He has been serving as Editor of Physics of Fluids since 1998.

7. 문 의 : 기계항공공학부 최해천 교수(choi@snu.ac.kr), 민경덕 교수(kdmin@snu.a.kr)