Abstract
When a viscous fluid flows over the surface of an object, different regions of the wall form different boundary layers. Fluctuating pressure in this boundary layer acts on the surface of the structure, causing it to vibrate and radiate noise; simultaneously, structural deformations will also have an impact on the flow field, and boundary layer pressure fluctuation is the most important component of flow noise. The characteristic parameters of a model, such as its wall thickness and the length of its parallel body section, will affect the pressure fluctuations it experiences. However, most studies treat the structure of the model as a rigid body. Therefore, this paper conducted experiments to examine the influences of the wall thickness and the parallel body length of a model on the pressure fluctuations it experiences. It was found that the fluctuating pressure at a given measuring position increases with decreasing wall thickness, and it decreases with increasing parallel body length. Then, this study demonstrated through comparative experiments that elastic and scale effects are important factors that cannot be ignored in calculations and experiments relating to pressure fluctuations. In addition, according to the characteristics of pressure fluctuation test values in different regions, the pressure-fluctuation prediction empirical formulas for different regions of the boundary layer were established or improved on the basis of previous research on pressure fluctuation in different regions of the boundary layer. Finally, by pasting a flow exciter at the transition position in the boundary layer of the model can keep its flow noise down, the experimental results show that rough particles can split the large vortex into smaller vortices and reduce flow noise by more than 5 dB. These results and empirical formulas provide references for numerical and experimental research examining pressure fluctuations.
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