Wall-Turbulence Structure with Pressure Gradient Around 2D Hump

Abstract

Direct numerical simulation around a two-dimensional hump shape is conducted at the Reynolds number $Re_{h} = 16,000$, based on the hump height. We investigate wall-turbulence structures around the hump in order to predict and control them to suppress separation. At this Reynolds number, specific striped wall-turbulence structure appears at the leading-edge near the wall surface. Its spanwise length-scale is close to that of the streak in a fully-developed turbulent channel flow. That is $\lambda _{y} = 0.08$ scaled with the hump height, which corresponds to $\lambda _{y}^{+} = 150$ in the local viscous unit. We identify two more different spanwise-correlated scales, $\lambda _{y} = 0.40$ and 0.13 around the hump. Spanwise length-scale of $\lambda _{y} = 0.40$ is around $\lambda _{y}^{+} = 600$. On the other hand, the other scale $\lambda _{y} = 0.13$ is not dependent on the local viscous scale.