水洞中突出矩形腔的流激驻波振荡研究

Study of Flow-Induced Standing Wave Resonance of Rectangular Cavity in Water Tunnel

在水洞中进行了变深度的、不带导流板的突出矩形腔在流激励下的振荡实验.对腔口附近壁面上几个典型点及腔底处测得的均方压力进行了谱分析,得到了许多有意义的结果.对驻波振荡,考虑到腔底的弹性边界作用,文中给出了推算水中腔底面反射系数的方法,得到了腔的驻波振荡频率修正公式.从修正公式得到的结果与其它腔深度的实验值比较,符合尚好.

This paper reports an experiment of flow-induced oscillation of a protruding rectangular cavity in the water tunnel.The spectra of fluctuating pressure on the bottom and test points on the wall are analyzed by HP3S62A Dynamic Signal Analyzer.The spectrum density of pressure, at cavity and at points inside the wall and at the leading edge, represents some line spectra at low Mach number.The relation of reflection coefficient of non-rigid bottom with standing wave resonance frequency is derived.From this relation and calculations, there is no doubt that the spectrum lines are the different order standing wave resonances of cavity with non-rigid bottom.The sound pressure spectrum density levels in cavity are increasing with the speed of water flow and with the depth of cavity.The total square pressure in the range(10-2510)Hz is approaching to 3.5-3.6 power of speed of flow at 3-9m /sec., and increases steeply as the cavitation occurs.The mean square pressure of frequency band(10-2150)Hz at different points on the wall is different in value, their levels are linearly increasing with respect to logarithm of speed.