Reynolds Stress Anisotropy in Self-Preserving Turbulent Shear Flows

Kurzfassung

It is theoretically shown that all turbulent shear flows governed by the boundary layer equations that exhibit self-preserving properties contain a layer, in which the Reynolds stress anisotropies are constant. Experimental data of several such flows are analysed, proving the existence of such a layer. The corresponding Reynolds stress anisotropies are inferred, deviating between the different flows. In particular, the shear stress anisotropy differs from the value in boundary layers according to the Bradshaw hypothesis, explaining the ``round-jet/plane-jet anomaly'' as well as the prediction of delayed re-attachment by models that are calibrated to boundary layer conditions. Requirements for the improvement of current RANS models are derived.