Abstract
When the wake characteristics of a flat plate blade supported by the wall were measured in a wind tunnel experiment in a uniform flow, the cell such an element of the coherent structure of the wake to the span direction will be maintained at a certain size. In this study, authors analyzed the generating mechanism and the steady characteristics of the coherent structure in the wake. According to the flow field visualized by a 3-dimensional numerical solver with the streamline and the normalized helicity, it was clarified that the streamwise vortices were generated in the wake. Then the vorticities Ωx formed regularly ten cells rotating alternately to the span direction. On the limiting stremline inside of the boundary layer on the blade surface, the same distribution as the vorticities Ωx in the wake occurred at the trailing edge, however, the regularity distribution did not exist at the leading edge or the almost inside region of the boundary layer. Moreover, when the vortex motion to the span direction was estimated by each production terms of the vorticity transport equation, the production of the vorticity Ωx by the Reynolds share stress ρv'w' was the largest among the production terms by turbulent flow, and it distributed structurally to the span direction. When it was summarized as if the motion of the Reynolds share stress ρv'w' formed a standing wave, authors pointed out that the condition which satisfied motion by the standing wave existed in the coherent structure at the far wake.
