軸対称急拡大管内における乱流中の渦構造と周波数特性に関するラージ・エディ・シミュレーション(流体工学,流体機械)

概要

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The present study performed large eddy simulation of turbulent separated and reattached flow through an axisymmetric sudden expansion, and clarified the relationship between vortex structures and frequency characteristics in the flow field. The separated shear layer stretched from the step becomes unstable, and rolls up into a vortex ring. The vortex ring is periodically shed downstream. This vortex becomes three-dimensional and breaks up into small vortices. As a result, circular transverse vortices are generated around the axis centerline. Downstream of the reattachment point, streamwise vortices also appear near the wall. The low flapping motion of the separated shear layer is observed around the step. On the other hand, the vortex ring is shed at higher frequency than that of the flapping motion. The low flapping motion causes the unsteadiness of the separated shear layer, and influences the shedding of the vortex ring. The shedding frequency of large-scale vortices from the reattachment region is also influenced by the flapping motion. Therefore, it is considered that the low frequency motion contributes to frequency characteristics of flow field. The present results are in good agreement with the previous experimental data.
一般社団法人日本機械学会の論文
2007-03-25