Experiments in bypass boundary layer transition under a stream with and without shear

15th Asian Congress of Fluid Mechanics

物理学;力学

Balamurugan, G.^1 ; Mandal, Alakesh C.^1

Department of Aerospace Engineering, Indian Institute of Technology, Kanpur, India^1

关键词: Boundary layer transitions;    Freestream turbulence;    Instability characteristics;    Low-speed wind tunnel;    Mean velocity profiles;    Non-uniform grids;    Particle image velocimetries;    Turbulence productions;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/822/1/012015/pdf
DOI  :  10.1088/1742-6596/822/1/012015

学科分类：力学，机械学

来源: IOP

【 摘 要 】

Effect of mean flow shear on bypass boundary layer transition is investigated experimentally in a low-speed wind tunnel. To initiate bypass transition on a flat plate, the level of freestream turbulence is intensionally enhanced using a uniform parallel rod grid and a non-uniform parallel rod grid. The non-uniform grid produces a mean velocity profile with shear, and therefore, turbulence production due to this shear will be non-zero compared to a uniform grid which produces a mean velocity profile without shear. The growth rate of the disturbance energy for the non-uniform grid is found to be higher compared to the uniform grid. The intermittency values are also found to be higher for the non-uniform grid under same flow conditions. Particle Image Velocimetry (PIV) measurements in the spanwise plane reveal instability characteristics similar to the one reported in the literature.