The effect of sweep-angle variation on the turbulence structure in a separated, three-dimensional flow

A three-dimensional separated flow behind a swept, backward-facing step is investigated by means of DNS for ReH = C∞H/v = 3000 with the purpose to identify changes in the statistical turbulence structure due to a variation of the sweep angle α from 0° up to 60°. With increasing sweep angle, the near-wall turbulence structure inside the separation bubble and downstream of reattachment changes due to the presence of an edge-parallel mean flow component W. Turbulence production due to the spanwise shear ∂W/∂y at the wall becomes significant and competes with the processes caused by impingement of the separated shear-layer. Changes due to a sweep angle variation can be interpreted in terms of two competing velocity scales which control the global budget of turbulent kinetic energy: the step-normal component U∞ = C∞ cos α throughout the separated flow region and the velocity difference C∞ across the entire shear-layer downstream of reattachment. As a consequence, the significance of history effects for the development into a two-dimensional boundary layer decreases with increasing sweep angle. For α ≥ 50°, near-wall streaks tend to form inside the separated flow region.     «

A three-dimensional separated flow behind a swept, backward-facing step is investigated by means of DNS for ReH = C∞H/v = 3000 with the purpose to identify changes in the statistical turbulence structure due to a variation of the sweep angle α from 0° up to 60°. With increasing sweep angle, the near-wall turbulence structure inside the separation bubble and downstream of reattachment changes due to the presence of an edge-parallel mean flow component W. Turbulence production due to the spanwise...     »