本文選題：水滴 + 無量綱數(shù)　； 參考：《沈陽農(nóng)業(yè)大學(xué)》2017年碩士論文

【摘要】：水滴是組成水流的基本單元,下泄的水流可以近似看成是由多個離散的水滴形成的連續(xù)下泄的水體。水流入水時產(chǎn)生的所有現(xiàn)象均可以通過改變單個水滴下落時的粒徑及高度進(jìn)行體現(xiàn),而水流入水的噪聲可以從單個水滴入手進(jìn)行分析,明確單個水滴入水時的水噪聲產(chǎn)生機(jī)理,然后通過噪聲的耦合關(guān)系對多個水滴入水水噪聲規(guī)律進(jìn)行研究,而此規(guī)律也是河道內(nèi)水工建筑物下泄水流的水噪聲規(guī)律。本文借助光學(xué)測試方法,利用i-SPEEDTR高速攝像機(jī)采集水滴入水過程的圖片,通過調(diào)整水滴大小及水滴下落高度進(jìn)行不同工況的試驗,用Photoshop圖像處理軟件和CAD制圖軟件對采集的圖像進(jìn)行后期處理和尺寸標(biāo)定,根據(jù)試驗結(jié)果對不同水滴入水現(xiàn)象進(jìn)行定性描述和定量分析。然后用ZonicBook專業(yè)振動噪聲分析系統(tǒng)對水滴入水產(chǎn)生的噪聲進(jìn)行時域信號和頻域信號采集,采用將產(chǎn)生水噪聲前一個周期波形圖作為背景噪聲波形圖,在對背景噪聲分離后將水噪聲的波形圖與高速攝像機(jī)采集到的水滴入水的現(xiàn)象相結(jié)合進(jìn)行分析,以確定水噪聲的產(chǎn)生機(jī)理,根據(jù)噪聲產(chǎn)生機(jī)理的不同對水噪聲進(jìn)行分類、噪聲影響因素進(jìn)行確定,通過縱向和橫向同時對比的方法確定各噪聲的頻域范圍,這在以往有關(guān)水噪聲問題的研究中是不多見的。為將水滴入水產(chǎn)生的噪聲與水流下泄水噪聲結(jié)合,根據(jù)水滴與水流的內(nèi)在關(guān)系,本文對多個水滴同時入水的噪聲進(jìn)行了測量,得到了水滴入水的普遍規(guī)律及相關(guān)關(guān)系。主要研究結(jié)論包括:(1)在水滴入水過程方面水滴入水現(xiàn)象分為:一次空腔、液滴飛濺、一次空腔回縮、中空射流、二次空腔、二次空腔回縮和液面振蕩現(xiàn)象,此外有時可能會出現(xiàn)水下初生氣泡和水下次生氣泡的隨機(jī)現(xiàn)象。對于同一個粒徑,在不同高度下落入水時We和無量綱高度Hd之間基本成冪函數(shù)關(guān)系,水滴粒徑越大,冪函數(shù)曲線的曲率越小;We和Re基本成冪函數(shù)關(guān)系,水滴粒徑越大,冪函數(shù)曲線的曲率越大;Ca2和We基本成線性關(guān)系,Fr和We基本成線性關(guān)系,水滴粒徑越大時該直線的斜率越大。此外不同入水現(xiàn)象對應(yīng)的Hd、We、Re、Fr和Ca的分布范圍也不盡相同,韋伯?dāng)?shù)We和雷諾數(shù)Re分布范圍比較有規(guī)律,而弗汝德數(shù)Fr、毛細(xì)數(shù)Ca和無量綱高度Hd的分布范圍比較分散。對于一次空腔現(xiàn)象We和Re呈現(xiàn)明顯的冪函數(shù)的相關(guān)關(guān)系,中空射流現(xiàn)象We和Re二次函數(shù)相關(guān)關(guān)系不明顯,二次空腔現(xiàn)象We和Re呈現(xiàn)較為明顯的冪函數(shù)相關(guān)關(guān)系,液滴飛濺現(xiàn)象We和Re呈現(xiàn)較明顯的二次函數(shù)相關(guān)關(guān)系。(2)在水滴水噪聲方面水噪聲的產(chǎn)生機(jī)理主要分為:脈動輻射噪聲、初生氣泡噪聲和次生氣泡噪聲,初生氣泡噪聲和次生氣泡噪聲是一種隨機(jī)現(xiàn)象,主要與水滴入水時否有初生氣泡和次生氣泡產(chǎn)生有關(guān)。不同粒徑的水滴在下落過程中的形變不同,粒徑越大,下落高度越高,下落過程中的水滴形狀不穩(wěn)定性越強(qiáng),所以噪聲產(chǎn)生的隨機(jī)性也越大。脈動輻射噪聲波形圖較紊亂,且振幅較小,噪聲響度較小,頻率范圍為50-500Hz,屬于低頻噪聲,噪聲音調(diào)較低;初生氣泡噪聲和次生氣泡噪聲為衰減的正弦波,最大振幅較大,噪聲響度較大,頻率范圍主要集中在中高頻,音調(diào)較高,且初生氣泡噪聲高頻現(xiàn)象更為明顯,頻率范圍為8000-20000Hz,次生氣泡噪聲的頻率范圍為500-20000Hz。當(dāng)多個水滴同時入水時,對于脈動輻射噪聲,瞬時聲壓最大值隨著入水水滴個數(shù)的增加呈現(xiàn)遞增趨勢;初生氣泡噪聲,瞬時聲壓最大值隨著入水水滴個數(shù)的增加呈現(xiàn)遞減趨勢;次生氣泡噪聲,隨著入水水滴個數(shù)的增加,次生氣泡噪聲瞬時聲壓最大值波動較大。
[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.
【學(xué)位授予單位】：沈陽農(nóng)業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O352;TB53

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1 田茹妍;水滴入水過程及其水噪聲試驗研究[D];沈陽農(nóng)業(yè)大學(xué);2017年

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本文編號：2020674