The Experimental Study Of Water Drop Process And Water Noise

Water is the basic unit of water and discharge water can be regarded as continuous discharge formed by a plurality of discrete droplets of water,all the phenomena of water flowing into the water can be reflected by changing the size and height of the drop.The noise of the water flowing into the water can be analyzed from a single drop of water,clear the water noise mechanism of a single drop,and then the noise law of several water droplets entering the water is studied by the coupling relation of noise,this law is also discharge flow water noise regularity of the hydraulic structures in river.In this paper,the i-SPEED TR high speed camera is used to capture the phenomenon of water dropping process,the experiments are carried out in different conditions by adjusting the drop size and drop height,and the images are processed by Photoshop and CAD software.Then,the qualitative description and quantitative analysis of the falling phenomenon of different droplets are carried out according to the experimental results.This experiment also uses the ZonicBook professional vibration and noise analysis system to collect the time domain signal and the frequency domain signal of the noise signal produced by water dropping process,a waveform diagram of the previous generation of water noise is used as the background noise,after the separation of the background noise,the water noise waveform and the phenomenon of the water droplets collected by the high-speed camera are analyzed to determine the mechanism of water noise.The classification of water noise and the influence factors of noise are determined according to the different mechanism of noise generation,and the frequency range of each noise is determined by the method of vertical and horizontal comparison,this study method on the problem of water noise is rare in previous studies.In order to combine the noise generated by water drop and the noise generated by the water flow,this paper measures the noise of several water droplets entering the water,and gets the universal law and relationship of water into the water based on the internal relationship between water drop and water flow.The main conclusions include:(1)Study on the water dropping processWater dropping process phenomena is divided into:primary cavity,droplet splash,primary cavity retraction,hollow jet,two cavity,two cavity retraction and liquid level oscillation,in addition,there may be random phenomena of underwater primary bubbles and underwater secondary bubbles.There is a power function relation between the We and the dimensionless height Hd when the same water falls into the water at different heights,besides the larger the droplet size,the smaller the curvature of the power function curve;the relationship between We and Re is basically a power function,the larger the droplet size,the larger the curvature of the power function curve;Ca2 and We are basically linear,Fr and We are basically linear,the larger the size of water droplets,the greater the slope of the straight line.In addition the distribution range of different water entry corresponding to Hd,We,Re,Fr and Ca are not the same,the Weber number We and the Reynolds number Re distribution is regular,however the Froude number Fr and the Capillary number Ca and the dimensionless height Hd is distributed.The relationship between We and Re for primary cavity phenomenon shows apparent power function correlation;the relationship between We and Re for hollow jet phenomenon shows not obvious two function correlation;the relationship between We and Re for two cavity phenomenon shows a more apparent power function correlation;the relationship between We and Re for droplet splash phenomenon shows a more obvious two function correlation.(2)Study on water droplet noiseThe mechanism of water noise can be divided into three parts:pulsating radiation noise,primary bubble noise and secondary bubble noise,the primary bubble noise and secondary bubble noise are random phenomena,which are mainly related to whether there are primary bubbles and secondary bubbles.The different particle size of the water droplets in the falling process of the deformation is different,the larger the size of water droplets,the stronger instability of the shape in the process of falling,so the randomness of the noise is also greater.Pulsating radiation noise waveform is disorder,the amplitude is small,and the loudness of noise is small,the frequency range is 50-500Hz,which belongs to the low frequency noise,and the voice of the noise is low.The primary and secondary air bubble noise are attenuation sine wave,the maximum amplitude is large,and the loudness of noise is large,the frequency range is mainly concentrated in the middle and high frequency,and the voice of the noise is high,and the high frequency phenomenon of the primary bubble noise is more obvious,frequency range of primary bubble noise is 8000-20000Hz,while the frequency range of secondary bubble noise is 500-20000Hz.When a number of water droplets into the water at the same time,for pulsating radiation noise,the maximum value of instantaneous sound pressure increases with the increase of the number of falling water droplets;for primary bubble noise,the maximum value of instantaneous sound pressure decreases with the increase of the number of falling water droplets;for secondary bubble noise,the maximum value of instantaneous sound pressure fluctuates greatly with the increase of the number of falling water droplets.