1504 Grazing Flow Effect to Acoustic Impedance of Perforated Surface with Very Small Diameter
Details
Introduction of perforations in the walls of flow surface causes not only significant sound attenuation but also reduction of aerodynamic sound radiation from a rotating wing. In order to enjoy the largest advantage of perforated surface, the optimal distribution of finite impedance should be realized, which means the impedance characteristics of the surface must be predicted under the grazing flow condition. In this paper grazing flow effect on the surface impedance was investigated by conducting a numerical simulation, where the diameter is 1mm and the Reynolds number based on the diameter ranges from 44 to 230. The complex surface impedance ratio marks far larger magnitude than the conventional impedance for larger diameters and higher Reynolds number, which reflects the effect of high viscosity of the flow.
