Effect of Yaw Angle on the Flow Structure of Low Aspect Ratio Elliptical Cavities

摘要

The flow regimes associated with a 2:1 aspect ratio, elliptical planform cavity in a turbulent flat-plate boundary layer have been systematically examined for various depth/width ratios (0.1-1.0) and yaw angles (0-90 degrees), using a combination of wind tunnel experiments (including particle image velocimetry) and computational fluid-dynamics (CFD) simulations. For each of the three categories specified according to yaw angle, which include the symmetric flow regime (yaw angle = 0 degrees), straight vortex regime (yaw angle = 90 degrees), and asymmetric flow regime (15 degrees = yaw angle = 60 degrees), different flow structures are found to exist depending on cavity depth. For each combination of yaw angle and depth, the flow has been analyzed through investigation of shear layer parameters, three-dimensional (3D) vortex structure, pressure distribution and drag, and wake flow. While the elliptical cavity flows have been found to have some similarities with those of nominally two-dimensional and rectangular cavities, the 3D effects due to the low aspect ratio and curvature of the walls give rise to features exclusive to low-aspect ratio elliptical cavities, including formation of cellular structures at intermediate depths and distinct vortex structures within and downstream of the cavity. The 3D structure of the flow is most pronounced in the asymmetric regimes with large yaw angles (45 and 60 degrees). The dominant feature in this regime is the formation of a trailing vortex that is associated with high drag. (C) 2017 American Society of Civil Engineers.