The noise generated by turbulent boundary layer flow over an axisymmetric body with a flat nose

Abstract

The noise generated by hydrodynamic flow over an axisymmetric body with a flat nose is described quantitatively. Flush‐mounted hydrophones were used to measure that part of the turbulent boundary‐layer pressure fluctuations that propagates as true sound. Power spectra of sound pressure were measured in a 200‐Hz to 150‐kHz frequency range over a wide range of Reynolds numbers (Ux D/ν = 2.52 × 10, where D is the diameter of the body) for the model operating in the China Ship Scientific Research Center 038 water tunnel. The power spectra of the noise measured in the laminar flow regions correspond little to those measured in the transition and fully developed turbulent regions of the flow. Free‐stream turbulence intensity and transition regions of the model were measured by using a laser doppler velocimeter. The transition regions have been compared with the computation results and it was found that they agreed rather well with the experiment. In addition to the experiment, 12 axisymmetric bodies were calculated and compared with the experiment. Results indicate that when the prismatic coefficient and DF/D is fixed, the model has fairly good flow properties. When DF/D is fixed and the prismatic coefficient is decreased, or the prismatic coefficient is fixed and the DF/D is decreased, separation point or transition point is delayed.