Surface flow visualisation over forward facing steps with varying yaw angle

The Science of Making Torque from Wind 2012

Rowcroft, J.^1 ; Burton, D.^1 ; Blackburn, H.M.^1 ; Sheridan, J.^1

School of Mechanical and Aerospace Engineering, Monash University, Clayton

VIC, Australia^1

关键词: Boundary layer thickness;    Effect of wind direction;    Reattachment length;    Spatial periodicity;    Step height;    Surface flow;    Surface shear stress;    Three-dimensional structure;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/555/1/012086/pdf
DOI  :  10.1088/1742-6596/555/1/012086

来源: IOP

【 摘 要 】

Many Australian wind farms are located near escarpments and cliffs where flow separation occurs. An absence of literature addressing the effect of wind direction over cliffs have motivated surface shear stress visualisations on forward facing steps at yaw angles between 0° and 50°. These visualisations have been conducted in the Monash University 450 kW wind tunnel. Mean reattachment lengths were measured and shown to vary as a function of the boundary layer thickness to step height ratio and the yaw angle. Vortices shed off the crest of the step induced surface shear stresses on the top surface of the step. The orientation of these shear stresses varied linearly with the yaw angle. Three-dimensional structures of different forms were also observed. At zero yaw angle the flow converged at points along the crest. At high yaw angles distinct sections of misaligned flow were observed downstream of the reattachment line, indicating a spatial periodicity in shedding.