有自由液面的陷落式圆腔流噪声实验研究

Experimental Research on Flow Noise of Circle Cavity with Free Surface

采用基于经验模态分解(EMD)的本征模态函数(IMF)分析法和对比实验法研究了有自由液面的陷落式圆腔的流噪声,实验流速为0.4m/s^2.0m/s,间隔0.2m/s。实验发现当流速为0.4m/s^0.6m/s时,腔内液体有明显的振荡现象,其表现形式为液体沿腔内深度方向的大幅上下运动,称为“活塞(Piston)”现象。当流速大于等于0.8m/s时,腔内无振荡现象出现。通过对背景噪声和腔流噪声的本征模态函数作对比分析,得到了腔内流噪声的特性。

Based on empirical mode decomposition（EMD） the towing tank for investigating the charactarithtic that a complicated data set can be decomposed into functions（IMF）. The acoustic data are collected wit method, a flow noise experiment is performed in of the noise. The key part of the EMD method is a finite and often small number of intrinsic mode h and without the cavity in every condition respectively. After the proceeding of empirical mode decomposition, the IMF of the acoustic data are got, and then the power spectrum density（PSD） spectrum of each IMF is done. Through comparing the difference of each PSD spectrum between the result of with and without cavity, the flow noise which results from the cavity can be got. In this experiment, when the flow velocity is from 0.4m/s to 0.6 m/s, the resonance phenomenon is observed. It shows that the water in the cavity is moved up and down in the deep direction. It is so called ＂Piston＂ phenomenon. When the flow velocity is more than 0.8m/s, there is no piston phenomenon any more. Then the flow noise which results from the shear layer and oscillation of the water can be got with the help of IMF method.