水流引起突出流线型柱腔共振的实验研究

在我国梅山水库试验水洞中,进行了流线型柱形腔的流激振荡实验研究.记录了不同流速情况下,腔中和腔土方的水听器输出噪声信号,同时记录了水洞试验段不同部位和腔壁上的加速度计输出振动信号.经过分析,发现突出试验段壁上的流线型腔与突出的矩形腔在气流中被激振荡相似,存在着其频率与流速无关的腔中液体声共振谱峰;同时,还发现其频率值与流速值成正比变化的流体动力共振谱峰.文章给出长140mm、宽28mm的流线型柱腔在腔深60mm和40mm两种情况下,其水流速度3～15m/s时,均方压力谱密度特征;给出前三阶液腔共振谱峰和前四阶流体动力共振谱峰的频率和谱级随流速变化的关系.

Experimental Investigation of Induced Resonant Oscillations of a Protruding Streamlined Cavity by Water Flow

In a water tunnel at Mei-Mountain reservoir, Anhui Province, the experiment of induced vibration of a protruding stream-lined cavity by water flow was carried out.The cavity is of 140mm.in length, 28mm.in width and 60mm.or 40mm.in depth.The velocity of water flow may vary from 3 to 15m/s.By spectrum anaiysis of the signals, out-put from hydrophones set on the bottom of cavity and above the opening of cavity, and out-put from accelerators stuck on the shell of cavity and wall of test-section of tunnel,it is found that there are two kinds vibrational resonance.One of them is the sound standing wave resonance of fluid in cavity, the frequencies of which are invariable as velocity of flow is increasing.The other is the fluid dynamic self-sustaining oscillation, the frequencies of which increase as velocity of flow is increasing.This phenomeon is similar to that we have found in case the cavity was put in wind tunnel.The mean square value of pressure of sound standing wave resonance in cavity varies with velocity of about 5-6 power.The Strouhal number/Characteristic length ratio is approximate to a constant, for definite depth of cavity and for certain order of self-sustaining oscillation.