縦渦列と干渉した乱流境界層の構造 : 縦渦列の性質と渦度分布(<小特集>乱流せん断流の制御)

概要

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An experiment study of a turbulent boundary layer that interacts with controlled longitudinal vortex arrays is presented. A row of vortices is produced by thin airfoils placed side by side in free stream. Five cases have been considered in which the spanwise period of vortices and their height are varied. The results show a very strong effect of the spanwise period as well as a notable effect of the height at which vortices are positioned. Namely, the spanwise period controls the vortex path and the vortices interaction with each other. A small period prevents vortices from interacting with the turbulent bounday layer but it also determines an effective vortex/vortex interaction, while a lager period is responsible for the vortices penetrating the inner layer and rebounding near wall and thus strongly interacting with the boundary layer, however, the vortex/vortex interaction is very weak. The vortex path affects the vortex strength: a high path and a small period lead to an abrupt decrement of vortex strength compared to the case when the path is low and the period is large. From the vorticity budget point of view, the small spanwise period leads to high variations of the vorticity flux. The large spanwise period, on the other hand, leads to a steadily decreasing vorticity flux except for a slight variation that is produced by the effect of the vortices axis changing at the rebounding points.
1997-01-25