Three-dimensional effects in turbulent shear layers*

Canonical turbulent boundary layers are known to be affected by introducing a skew in the mean flow, with some observations including reduction in turbulent shear stress and drag in the initial transient. However, similar insights are lacking for turbulent shear layers. We are using direct numerical simulations (DNS) to study the qualitative and quantitative effects of three-dimensionality in shear layers. We consider an idealized version of the problem where two turbulent boundary layers with different freestream velocity vectors, say developing on either side of a splitter plate, come together to create a turbulent shear layer. In the long-time limit, the skewed shear layer behaves like its planar counterpart, albeit in a different frame of reference. This suggests that the three-dimensional effects, if any, are limited to the initial transient. Therefore, the current work is aimed at quantifying the extent and timescale of these transient three-dimensional effects.