水滴入水过程及其水噪声试验研究

发布时间：2018-06-15 04:32

本文选题：水滴 + 无量纲数　；参考：《沈阳农业大学》2017年硕士论文

【摘要】：水滴是组成水流的基本单元,下泄的水流可以近似看成是由多个离散的水滴形成的连续下泄的水体。水流入水时产生的所有现象均可以通过改变单个水滴下落时的粒径及高度进行体现,而水流入水的噪声可以从单个水滴入手进行分析,明确单个水滴入水时的水噪声产生机理,然后通过噪声的耦合关系对多个水滴入水水噪声规律进行研究,而此规律也是河道内水工建筑物下泄水流的水噪声规律。本文借助光学测试方法,利用i-SPEEDTR高速摄像机采集水滴入水过程的图片,通过调整水滴大小及水滴下落高度进行不同工况的试验,用Photoshop图像处理软件和CAD制图软件对采集的图像进行后期处理和尺寸标定,根据试验结果对不同水滴入水现象进行定性描述和定量分析。然后用ZonicBook专业振动噪声分析系统对水滴入水产生的噪声进行时域信号和频域信号采集,采用将产生水噪声前一个周期波形图作为背景噪声波形图,在对背景噪声分离后将水噪声的波形图与高速摄像机采集到的水滴入水的现象相结合进行分析,以确定水噪声的产生机理,根据噪声产生机理的不同对水噪声进行分类、噪声影响因素进行确定,通过纵向和横向同时对比的方法确定各噪声的频域范围,这在以往有关水噪声问题的研究中是不多见的。为将水滴入水产生的噪声与水流下泄水噪声结合,根据水滴与水流的内在关系,本文对多个水滴同时入水的噪声进行了测量,得到了水滴入水的普遍规律及相关关系。主要研究结论包括:(1)在水滴入水过程方面水滴入水现象分为:一次空腔、液滴飞溅、一次空腔回缩、中空射流、二次空腔、二次空腔回缩和液面振荡现象,此外有时可能会出现水下初生气泡和水下次生气泡的随机现象。对于同一个粒径,在不同高度下落入水时We和无量纲高度Hd之间基本成幂函数关系,水滴粒径越大,幂函数曲线的曲率越小;We和Re基本成幂函数关系,水滴粒径越大,幂函数曲线的曲率越大;Ca2和We基本成线性关系,Fr和We基本成线性关系,水滴粒径越大时该直线的斜率越大。此外不同入水现象对应的Hd、We、Re、Fr和Ca的分布范围也不尽相同,韦伯数We和雷诺数Re分布范围比较有规律,而弗汝德数Fr、毛细数Ca和无量纲高度Hd的分布范围比较分散。对于一次空腔现象We和Re呈现明显的幂函数的相关关系,中空射流现象We和Re二次函数相关关系不明显,二次空腔现象We和Re呈现较为明显的幂函数相关关系,液滴飞溅现象We和Re呈现较明显的二次函数相关关系。(2)在水滴水噪声方面水噪声的产生机理主要分为:脉动辐射噪声、初生气泡噪声和次生气泡噪声,初生气泡噪声和次生气泡噪声是一种随机现象,主要与水滴入水时否有初生气泡和次生气泡产生有关。不同粒径的水滴在下落过程中的形变不同,粒径越大,下落高度越高,下落过程中的水滴形状不稳定性越强,所以噪声产生的随机性也越大。脉动辐射噪声波形图较紊乱,且振幅较小,噪声响度较小,频率范围为50-500Hz,属于低频噪声,噪声音调较低;初生气泡噪声和次生气泡噪声为衰减的正弦波,最大振幅较大,噪声响度较大,频率范围主要集中在中高频,音调较高,且初生气泡噪声高频现象更为明显,频率范围为8000-20000Hz,次生气泡噪声的频率范围为500-20000Hz。当多个水滴同时入水时,对于脉动辐射噪声,瞬时声压最大值随着入水水滴个数的增加呈现递增趋势;初生气泡噪声,瞬时声压最大值随着入水水滴个数的增加呈现递减趋势;次生气泡噪声,随着入水水滴个数的增加,次生气泡噪声瞬时声压最大值波动较大。
[Abstract]:The water drop is the basic unit of the flow of water. The flow of water can be regarded as a continuous discharge water body formed by a number of discrete drops. All the phenomena produced by the flow of water can be reflected by the change of the size and height of the drop of a single water drop, and the noise of the water flowing into the water can be divided into a single water drop. An analysis is made of the mechanism of water noise generated by a single drop of water, and then the noise law of water drops into water is studied by the coupling relationship of noise. This law is also the law of water noise in the discharge of water in a watercourse. In this paper, a i-SPEEDTR high speed camera is used to collect water drop into the water. By adjusting the size of water droplets and the drop height of water droplets for different working conditions, the images are processed and calibrated by Photoshop image processing software and CAD drawing software. According to the test results, the water droplet entry phenomenon is qualitatively described and determined. Then the professional vibration and noise of ZonicBook is divided. The noise of water drop into water is collected in time domain signal and frequency domain signal. A periodic wave pattern before the production of water noise is used as the background noise waveform. The analysis of the wave pattern of water noise and the phenomenon of water drop collected by high speed camera after the background noise separation is combined to determine the water noise. The water noise is classified according to the difference of the noise generation mechanism, the influence factors of the noise are determined, and the frequency range of the noise is determined by the simultaneous comparison between the vertical and the horizontal. This is not much in the previous research on the water noise problem. According to the internal relationship between water drop and water flow, the noise of multiple water drops at the same time is measured, and the universal law and correlation of water drop into water are obtained. The main conclusions are as follows: (1) the water droplet entry phenomenon is divided into one space cavity, droplet splash, one cavity retracting, hollow jet, two space The cavity, the two cavity retracting and the liquid surface oscillation phenomenon, and sometimes the random phenomena of the underwater primary bubble and the next gas bubble may occur. For the same particle size, the relationship between the We and the dimensionless height Hd is basically a power function relationship, the larger the diameter of the water droplets, the smaller the curvature of the power function curve, and the basic formation of We and Re. The larger the power function relation, the larger the droplet diameter, the greater the curvature of the power function curve, the linear relationship between Ca2 and We, the linear relationship between Fr and We, the greater the slope of the line when the water droplet size is bigger. Besides, the distribution range of the corresponding Hd, We, Re, Fr and Ca is also different, and the Weber number We and the Re distribution range of Reynolds number are compared. The distribution of the freoude number Fr, the number of capillary number Ca and the dimensionless height Hd are scattered. For the primary cavity, the correlation between We and Re is obvious, the correlation of the hollow jets We and Re two functions is not obvious, the two cavity phenomenon We and Re show a more obvious power function correlation, and the droplet splashing is present. The relationship between We and Re shows a more obvious two function correlation. (2) the mechanism of water noise in water drop water noise is mainly divided into pulsating radiation noise, primary bubble noise and secondary bubble noise, primary bubble noise and secondary bubble noise are a random phenomenon, and the primary bubble and secondary bubble production are mainly produced when water drops into water. The higher the particle size, the higher the drop height, the stronger the drop shape in the falling process, the more random the noise produced, the more chaotic, the smaller amplitude, the smaller noise and the frequency range of 50-500Hz, which belongs to the low frequency noise. The noise of sound and noise is lower, the noise of primary bubble and secondary bubble is a sinusoidal wave, the maximum amplitude is larger, the noise loudness is larger, the frequency range is mainly concentrated in the middle and high frequency, the tone is high, and the frequency range of primary bubble noise is more obvious, the frequency range is 8000-20000Hz, the frequency range of secondary bubble noise is 500-20000Hz. when it is used. The maximum value of instantaneous sound pressure increases with the increase of the number of water droplets, the maximum value of the initial bubble noise and the instantaneous sound pressure decrease with the increase of the number of water droplets, and the secondary bubble noise, with the increase of the number of water droplets, the secondary bubble noise instantaneous sound, the maximum value of instantaneous sound pressure increases with the increase of the number of water drops. The maximum pressure fluctuates greatly.
【学位授予单位】：沈阳农业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O352;TB53

【相似文献】