【摘要】：由于有機(jī)物質(zhì)分解等原因,實際的海底沉積物中存在氣泡,氣泡的存在會顯著影響沉積物低頻段的聲學(xué)特性,因此研究氣泡對沉積物低頻段聲速的影響機(jī)理具有重要意義.考慮到外場環(huán)境的不可控性,在室內(nèi)水池中搭建了大尺度含氣非飽和沙質(zhì)沉積物聲學(xué)特性獲取平臺,在有界空間中應(yīng)用多水聽器反演方法首次獲取了含氣非飽和沙質(zhì)沉積物300—3000 Hz頻段內(nèi)的聲速數(shù)據(jù)(79—142 m/s),并同時利用雙水聽器法獲取了同一頻段的數(shù)據(jù)(112—121 m/s).在聲波頻率遠(yuǎn)低于沉積物中最大氣泡的共振頻率時,根據(jù)等效介質(zhì)理論,將孔隙水和氣泡等效為一種均勻流體,改進(jìn)了水飽和等效密度流體近似模型.模型揭示了氣泡對沉積物低頻段聲學(xué)特性的影響規(guī)律,理論上解釋了沉積物中聲速的降低.通過分析模型預(yù)報聲速對模型參數(shù)的敏感性,根據(jù)測量得到的聲速分布反演得到了沉積物不同區(qū)域的氣泡體積分?jǐn)?shù),氣泡體積分?jǐn)?shù)從1.07%變化到2.81%.改進(jìn)的模型為沉積物中氣泡體積分?jǐn)?shù)估計提供了一種新方法.
[Abstract]:Due to the decomposition of organic matter, there are bubbles in the actual seafloor sediments, and the existence of bubbles will significantly affect the acoustic characteristics of sediments at low frequency. Therefore, it is of great significance to study the influence mechanism of bubbles on the acoustic velocity of sediments at low frequency. Considering the uncontrollability of the field environment, a large-scale platform for obtaining the acoustic characteristics of gas-bearing unsaturated sandy sediments has been built in an indoor pool. The acoustic velocity data (79-142 m / s) in the 300-3000 Hz band of gas-bearing unsaturated sandy sediments were obtained for the first time in bounded space by using the multi-hydrophone inversion method. At the same time, the data of the same frequency band (112-121 m / s) were obtained by double hydrophone method. When the acoustic frequency is far lower than the resonance frequency of the largest bubble in sediment, the pore water and bubble are equivalent to a homogeneous fluid according to the theory of equivalent medium, and the approximate model of water saturated equivalent density fluid is improved. The model reveals the influence of bubbles on the acoustic characteristics of sediments at low frequency and theoretically explains the decrease of sound velocity in sediments. By analyzing the sensitivity of the model prediction velocity to the model parameters, the bubble volume fraction in different areas of sediment was obtained by inversion of the measured sound velocity distribution, and the bubble volume fraction changed from 1.07% to 2.81%. The improved model provides a new method for estimating bubble volume fraction in sediment.
【作者單位】： 哈爾濱工程大學(xué)水聲技術(shù)重點實驗室;哈爾濱工程大學(xué)水聲工程學(xué)院;
【基金】：國家自然科學(xué)基金(批準(zhǔn)號:11274078)資助的課題~~
【分類號】：O427

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