F301 VORTICAL STRUCTURES AND TURBULENCE STATISTICS OF THE PERIODICALLY PERTURBED SEPARATED FLOW OVER THE BACKWARD-FACING STEP(Control of turbulent mixing process)

概要

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The perturbation-frequency characteristics of the momentum transfer enhancement were experimentally investigated. The periodically perturbed turbulent separated flow over a backward-facing step was chosen for the test case. A particle imaging velocimeter (PIV) was applied to the flow field measurement. The obtained velocity data were phase-averaged, synchronized with the perturbation, so that the periodic motion associated with the perturbation can be extracted. The phase-averaged flow structure showed the successive evolution of spanwise large-scale vortical structure in the separated shear layer. When perturbed with the most effective frequency on the reattachment promotion, 2 or 3 vortical structures were introduced into the recirculating region, increasing the Reynolds stress there, enabling the enhancement of the reattachment promotion. This perturbation assisted naturally existing vortical structures in growing their size. On the other hand, the lower and higher frequency perturbations had less effect because they introduced lower number of vortical structures into the separated shear layer.
一般社団法人日本機械学会の論文
2000-10-01