A Study of Coherent Structure of the Wake of a Flat Plate Blade Generated to the Span Direction : 2nd. Report : Relationship between the Standing Wave and the Aero-acoustic Sources

The coherent structure at high Reynolds number accompanied with the turbulence, which passed across a flat plate blade, was analyzed by the wind tunnel test. The span-wise correlation length related to the aero-acoustic sources has been assumed as a statistical experimental equation based on this structure; also this length has been applied as the scale of the source in the prediction theory of the turbulent noise generated from a fan. This parameter is commonly used in the prediction equation; nevertheless it is still unknown whether the momentum of the coherent structure is conserved at where of the developed boundary layer or the wake. In this paper, the 3-dimensional coherent structure of a flat plate blade in the wake is clarified as the following; the coherent structure to the span direction is formed by a cell of the Reynolds shear stress pv'w', and the pv'w' forms the standing wave in the wake, moreover, the standing wave forms structural aero-acoustic sources at the trailing edge side on the surface of a flat plate blade.
長崎大学工学部研究報告 Vol.33(60) p.9-17, 2003