Manipulation of uniformly sheared turbulence using curvature and thin ribbons.

Abstract

A nearly homogeneous uniformly sheared turbulent flow was subjected to curvature in the same direction as the mean shear and then to curvature reversal. The adjustment of the turbulence structure to a change of the value of the curvature parameter, $S={{\overline{U}\sb{c}\over R\sb{c}}\over{\partial\overline {U}\over\partial\sb{n}}}$, is investigated. The structural parameter, $K\sb{uv}={\overline{uv}\over{q\sp2}}$, adjusts faster when the effects of curvature are stronger. For the small values of S obtained in the present investigation the adjustment of $K\sb{uv}$ depends on both the original and new values of S as the flow is subjected to curvature reversal. Qualitative and quantitative similarities between the present flow and curved turbulent boundary layers are identified. A thin ribbon is placed in rectilinear and curved nearly homogeneous uniformly sheared flows. The development of the wake of the thin ribbon is investigated. The mean flow characteristics of the wake of the thin ribbon developing in rectilinear shear flow present a certain degree of self similarity and some resemblance to the characteristics of the wake of a LEBU in the outer part of turbulent boundary layers.