浪流条件下月池内流体活塞振荡特性实验研究

在浪流实验条件下研究了圆形月池内流体的活塞振荡特性.在浪流的条件下,月池内的流体在不同波浪周期时表现出不同的活塞振荡特性.通过对实验现象及结果的分析,认为在浪流条件下月池内流体的活塞振荡存在着某种分岔现象,当波浪频率相对于月池内流体活塞振荡固有频率为低频时,月池内流体的振荡为强迫振荡,以浪流遭遇频率进行振荡;当浪流遭遇频率不变,波浪频率略有变化,在某一临界值附近时,月池内流体的振荡发生突变,表现出类似于自激振荡的特性,并以活塞振荡固有频率进行振荡.在来流为浪流时,月池内流体的活塞振荡特性由波浪频率和月池内流体活塞振荡固有频率构成的无量纲的Cf所决定,对于该值存在着临界值Cfe,当Cf>Cfe时,月池内流体的活塞振荡类似于自激振荡的特性;当Cf

Experimental research on piston oscillating behavior of fluid in a moonpool with wave-flow

This paper studies the piston oscillation of fluid in a circular moonpool under various states of water-flow.The research was conducted in a towing tank of Harbin Engineering University,a circular moonpool with a diameter of 0.3m and a depth of 0.4 m.The experiment indicated that the oscillation patterns of the water in the moon pool vary greatly.When the frequency of wave is lower than that of the piston oscillation of!fluid,the oscillation resembles a forced vibration with the wave-flow encountering frequency;but when the wave-flow frequency is constant and the wave frequency changes a little,the oscillation of fluid in the moonpool will have an abrupt change at the vicinity of certain critical frequency,showing that the behaviors resemble the self-induced vibration with the natural frequency of piston vibration.When there is wave-flow,the oscillating characteristic of the water in the moon pool is determined by Cf,a dimensionless quantity related to the wave frequency and the natural frequency of piston oscillation.There exists a critical value for Cf,i.e.Cfe. When Cf >Cfe,the oscillation of the water in the moon pool resembles a self-induced oscillation,when Cf