A COMBINED EXPERIMENTAL AND NUMERICAL INVESTIGATION OF ROUGHNESS INDUCED SUPERSONIC BOUNDARY LAYER TRANSITION etc15 Tracking Number 247Presentation: Session: Instability and Transition 2 Room: Room A Session start: 15:00 Tue 25 Aug 2015 Yunfei Zhao zhaoyf08@126.com Affifliation: Department of Areospace Science and Engineering, National University of Defense Technology, Changsha, P. R. China, 410073 Wei Liu fishfather6525@sina.com Affifliation: Department of Areospace Science and Engineering, National University of Defense Technology, Changsha, P. R. China, 410073 Xiaoliang Yang yangxl_nudt@sina.com Affifliation: Department of Areospace Science and Engineering, National University of Defense Technology, Changsha, P. R. China, 410073 Shihe Yi yishihe@nudt.edu.cn Affifliation: Department of Areospace Science and Engineering, National University of Defense Technology, Changsha, P. R. China, 410073 Xiaogang Deng Xgdeng2000@vip.sina.com Affifliation: Department of Areospace Science and Engineering, National University of Defense Technology, Changsha, P. R. China, 410073 Topics: - Instability and transition Abstract: The laminar-turbulent transition of a supersonic flat-plate boundary layer with isolated roughness element is investigated both numerically and experimentally. Experiments are conducted in a Mach 3 low-noise wind tunnel for three different roughness heights of 1mm, 2mm and 4mm respectively. The flow structures in the transitional boundary layer are measured by a nano-based planar laser scattering (NPLS) flow visualization technique. Calculations are implemented in the same wind tunnel conditions using both second-order scheme and fifth-order weighted compact nonlinear scheme (WCNS-E-5) for comparison. Good agreements are achieved between experimental data and high-order solutions, including the turbulent boundary layer structures and quantitative pressure distribution along the plate centerline. However, the second-order scheme is found to be too dissipative to resolve the unsteadiness and small-scale structures in the transitional flow field. It is observed that the shear layer instability appears to be the leading mechanism for transition to turbulence in the wake of roughness element. With increasing height of roughness, the shear layer breaks up earlier and the transition tends to move forward. |