气泡体积分数对沙质沉积物低频声学特性的影响
发布时间：2018-12-14 23:29
【摘要】：由于有机物质分解等原因,实际的海底沉积物中存在气泡,气泡的存在会显著影响沉积物低频段的声学特性,因此研究气泡对沉积物低频段声速的影响机理具有重要意义.考虑到外场环境的不可控性,在室内水池中搭建了大尺度含气非饱和沙质沉积物声学特性获取平台,在有界空间中应用多水听器反演方法首次获取了含气非饱和沙质沉积物300—3000 Hz频段内的声速数据(79—142 m/s),并同时利用双水听器法获取了同一频段的数据(112—121 m/s).在声波频率远低于沉积物中最大气泡的共振频率时,根据等效介质理论,将孔隙水和气泡等效为一种均匀流体,改进了水饱和等效密度流体近似模型.模型揭示了气泡对沉积物低频段声学特性的影响规律,理论上解释了沉积物中声速的降低.通过分析模型预报声速对模型参数的敏感性,根据测量得到的声速分布反演得到了沉积物不同区域的气泡体积分数,气泡体积分数从1.07%变化到2.81%.改进的模型为沉积物中气泡体积分数估计提供了一种新方法.
[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.
【作者单位】： 哈尔滨工程大学水声技术重点实验室;哈尔滨工程大学水声工程学院;
【基金】：国家自然科学基金(批准号:11274078)资助的课题~~
【分类号】：O427
[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.
【作者单位】： 哈尔滨工程大学水声技术重点实验室;哈尔滨工程大学水声工程学院;
【基金】：国家自然科学基金(批准号:11274078)资助的课题~~
【分类号】：O427
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