水体悬浮颗粒声学测量技术研究

发布时间：2018-01-21 02:48

本文关键词： 悬浮颗粒浓度悬浮颗粒粒径反向散射回波多频反向散射反演方法　出处：《浙江大学》2015年硕士论文　论文类型：学位论文

【摘要】：基于声学的水体悬浮颗粒测量是研究水中悬沙浓度分布、迁移等特征的重要手段。相比于传统的悬浮颗粒观测技术,基于声学的方法是一种非干扰式剖面测量方法,这种方法操作简易、测量数据具有较高的空时分辨力,近年来受到越来越多的关注,但其涉及的声信号处理技术相对复杂。论文针对声学反向散射技术运用在水体悬浮颗粒浓度剖面测量过程中的若干问题开展研究,旨在探索有效的悬浮颗粒浓度声学反演方法。声学反向散射测量方法的基本原理为：发射换能器发射短时声脉冲信号照射水体,水体内悬浮物质散射声能,接收换能器记录沿着发射的反方向传播回来的回波信号；回波信号携带了悬浮物质的物理特征,通过声学反演的方法可以从中获取相关物理特征参数。在声学测量过程中需要特别考虑悬浮颗粒自身对声波造成的衰减,以及悬浮颗粒大小和浓度对散射声能量的联合贡献等问题。论文针对声波散射的衰减特性,分别介绍其几何扩展衰减与吸收衰减,并分别从效声学截面积和散射形式函数两个方向对悬浮颗粒的散射特性进行探讨。在此基础上,论文首先以宽带声学多普勒流速剖面仪(Acoustic Doppler Current Pro-filer,简称ADCP)为例,介绍了一种宽带水体散射回波的构建方法,即通过对宽带ADCP测量过程中的发射信号、声波传播过程的能量变化进行分析,在频率域对各个频率分量分别进行处理,最后利用傅里叶合成重构水体的反向散射回波。通过仿真分析表明该方法构建的散射回波在统计意义的角度与实测环境信号有较好的一致性。论文对基于声学反向散射的悬浮颗粒浓度和粒径的反演方法进行了研究,根据测量频率的使用情况将其划分为单频和多频反演技术,主要探讨单频浓度反演中的衰减修正问题、双频浓度反演方法以及多频的粒径反演方法(能量比算法、差值算法和最近邻算法)。论文同时从多参数优化的角度出发,探讨粒子群优化算法(Particle Swarm Optimization,简称PSO)在悬浮颗粒反演方面的应用。通过对仿真数据进行反演分析,探讨300kHz单频浓度反演算法,200、300、500kHz多频率粒径和浓度反演算法的性能。最后介绍一种专用水体特性剖面测量系统的实现方案,包括系统整体架构、电子硬件模块设计、软件设计等。通过利用宽带ADCP与研制的试验系统进行多次的实际海洋环境数据采集,并对采集数据应用论文所研究的算法进行处理分析,验证了系统方案与算法实现的有效性。
[Abstract]:The measurement of suspended particles in water based on acoustics is an important means to study the characteristics of suspended sediment concentration distribution and transport in water, compared with the traditional suspended particle observation technology. Acoustic-based method is a non-interference profile measurement method, which is easy to operate and has a high space-time resolution. In recent years, more and more attention has been paid to the measurement data. However, the acoustic signal processing technology involved is relatively complex. This paper focuses on the application of acoustic backscattering technology in the measurement of suspended particle concentration profile. The aim of this paper is to explore an effective method for acoustic inversion of suspended particle concentration. The basic principle of acoustic backscatter measurement method is that transmitting transducer emits short-time acoustic pulse signal to water body and scattering sound energy of suspended matter in water body. Receiving the transducer to record the echo signal propagating in the opposite direction of the transmission; Echo signals carry the physical characteristics of suspended matter, and the relevant physical parameters can be obtained by acoustic inversion. In the acoustic measurement process, special consideration should be given to the attenuation of acoustic waves caused by suspended particles themselves. The joint contribution of suspended particle size and concentration to scattering sound energy is also discussed. According to the attenuation characteristics of acoustic scattering, the geometric spread attenuation and absorption attenuation are introduced in this paper. The scattering characteristics of suspended particles are discussed from two directions: the effective acoustic cross section area and the scattering form function. Firstly, the paper takes the broadband acoustic Doppler velocity profiler (ADCP) as an example. In this paper, a method of constructing the scattering echo of wide band water body is introduced, that is, the energy change of the acoustic wave propagation process is analyzed by analyzing the emission signal in the process of broadband ADCP measurement. Each frequency component is processed separately in frequency domain. Finally, the inverse scattering echo of reconstructed water is synthesized by Fourier transform. The simulation results show that the backscattering echo constructed by this method is in good agreement with the measured environmental signal at the angle of statistical significance. In this paper, the inversion method of suspended particle concentration and particle size based on acoustic backscattering is studied, and it is divided into single frequency and multi-frequency inversion technology according to the use of measurement frequency. This paper mainly discusses the problem of attenuation correction in single-frequency concentration inversion, dual-frequency concentration inversion method and multi-frequency particle size inversion method (energy ratio algorithm). The difference algorithm and the nearest neighbor algorithm are discussed in this paper. At the same time, from the point of view of multi-parameter optimization, particle swarm optimization (PSO) algorithm is discussed. The application of PSOs in the inversion of suspended particles is discussed. The inversion algorithm of 300kHz single frequency concentration is discussed through the inversion analysis of the simulation data. Performance of 500 kHz multi-frequency particle size and concentration inversion algorithm. Finally, a special water profile measurement system is introduced, including the whole structure of the system and the design of electronic hardware module. Software design. Through the use of broadband ADCP and the developed experimental system for the actual marine environment data acquisition, and the collection of data application of the algorithm studied in the paper for processing and analysis. The validity of the scheme and algorithm is verified.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P715

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