はく離せん断層における渦度の消失(流体工学,流体機械)  [in Japanese] Decay of Vorticity in Separated Shear Layer(Fluids Engineering)  [in Japanese]

In this study, process of vorticity decay caused by viscous interaction in a separated shear layer was investigated based on velocity measurements and flow visualization of the separated shear layer in the very vicinity of the separation point of a test body. A right isosceles triangular prism with two 200mm long isosceles sides was used as the test body, and the experiment was carried out at the fixed Reynolds number of 19000. As the results, following aspects were clarified about the vorticity decay. i) A part of the vorticity decay in the separated share layer behind a body was caused by viscous interaction associated with transition of velocity distribution from boundary layer like shape to free shear layer like shape in the very vicinity of the separation point. ii) The Reynolds shear stress associated with turbulent dissipation does not take part in the vorticity decay process in the very vicinity of the separation point. iii) Since the Reynolds shear stress about an intermediate size vortex produced by coalescence of smaller vortices was considerably large, the flow field becomes turbulent and three dimensional by the coalescence of the smaller vortices.