V.A.Voskoboinick, V.T.Grinchenko, A.P.Makarenkov Pseudo-sound behind the obstacle on a cylinder in axial flow |
Acoustic bulletin, Vol. 5 ¹ 1, (2002) |
| Pseudo-sonic fluctuations of the wall pressure behind a ring-type obstacle on longitudinally streamlined flexible extended cylinder are experimentally investigated. Integral and spectral statistical characteristics of a fluctuating pressure field behind the obstacle are obtained and its influence on structure of turbulent boundary layer is investigated. Installation of the obstacle in the internal area of the boundary layer changes total structure of the boundary layer. The intensity of the wall pressure fluctuations increases with the increase of diameter of the obstacle. The maximal values of intensity are observed in the near wake of the obstacle. At distances exceeding 100 diameters of the obstacle the turbulent boundary layer becomes restored. An increase of diameter of the obstacle and the flow velocity results in growth of the low-frequency spectral components of the pressure fluctuations and decay of the high-frequency components, when comparing with a boundary layer on hydraulically smooth cylinder. The turbulent boundary layer behind the obstacle is saturated with the large-scale vortical structures. The maximal contribution to energy of the field of pseudo-sonic pressure fluctuations is done by the vortices shedding from the cross-flowed obstacle, which frequencies correspond to the Strouhal number Sh≈0.1. For pre-crisis regime of the separation flows on the ring obstacle the Strouhal number changes inversely to the Reynolds number. |
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KEY WORDS: pseudosound, flow around obstacles, boundary layer, the intensity of fluctuations, scale of vortices |
| TEXT LANGUAGE: Russian |