Research on 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 (U∞D/ν 2.52×10, where D is the diameter of the body) for the model operating in the China Ship Scientific Research Center 03B 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 on the model were measured by using a laser-Doppler velocimeter. The transition regions have been compared with the computation results and found to agree rather well with experiment. In addition to the experiment, 12 axisymmetric bodies are calculated and compared with the experiment. Results indicate that when the prismatic coefficient and DF/D are fixed, the model has fairly good flow properties. When DF/D is fixed and the prismatic coefficient is decreased, or the prismatic is fixed and the DF/D is decreased, the separation point or transition point is delayed.