舰船尾流气泡层散射相位函数的计算与分析

利用Mie散射理论及其递推公式并结合舰船尾流气泡的测量结果,得到了舰船尾流中气泡群的散射相位函数。通过对散射相位函数的分析与讨论,得出：尾流存在时间及气泡群分布模型参数的变化对散射相位函数的影响较小,仅当小半径气泡密度增加时其后向散射强度略有减小;尾流气泡相对于海水的折射率变化是影响尾流气泡群散射相位函数的主要因素,相对折射率越大,后向散射越弱。     

水中气泡幕的多体多次声散射模型分析

通过引入水中气泡群分布函数,建立了气幕多体多次声散射模型.与多体一次散射模型相比,多体多次声散射模型能够更加真实地反映出具有较高体积浓度气幕的声散射特性,因此,它是分析声波在气幕介质中反射和透射问题的重要基础.     

实船尾流气泡对太阳光散射特性的影响

由于到达海表面的太阳光的主要能量分布在0.15～4 μm之间,且海水的透过窗口也在此范围内,太阳光在海水中具有一定的穿透能力.在海水中尾流气泡受到太阳光的照射会对其有明显的散射作用.利用尾流气泡太阳光散射特性与海水散射特性的差异可对尾流进行探测.本文利用Mie散射理论对尾流气泡的太阳光散射特性进行了研究,并在真实海洋环境中对海水及实船太阳光散射特性进行了试验研究.研究表明,以太阳光作为光源,在一定深度可以探测到尾流气泡太阳光散射特性.     

尾流气泡声散射规律研究

通过对气泡半径与其所在深度的关系以及单个气泡散射面积的分析,研究了气泡上浮过程中气泡散射的变化规律。研究结果表明,满足散射峰值频率—深度条件时,气泡散射最强。     

大气散射对激光制导武器对抗影响研究

为了避免大气散射给激光制导武器对抗带来的不利影响,利用激光信号在近地大气中传输的Mie散射模型,讨论了气溶胶霾粒子引起的能量衰减和后向散射能量密度的计算方法,数值模拟了激光制导武器最大作用距离与大气能见度之间的关系,定量计算了激光目标指示器与导引头不同距离时的激光大气后向散射能量密度,结合场区条件给出了配置点位的具体要求,为激光制导武器对抗态势构建提供参考依据.     

舰船尾流后向光学检测方法研究

舰船在航行过程中会在尾部产生大量的气泡,通过检测气泡可以有效的跟踪船舶。本文在Monte Carlo模型的基础上研究激光脉冲后向散射特性,并进行后散射信号的特征提取,获得其频域特性。最后进行仿真实验,通过仿真结果可以看出,通过气泡对信号的后沿位置、时域宽度、峰值大小和位置、能量和形状等的影响,可以有效的检测到气泡,确定出船舶的位置。     

基于声散射的鱼雷自噪声场空间特性

基于螺旋桨噪声经声散射形成的自噪声理论模型,利用散射点回波原理,采用散射元时间信号叠加模型进行研究,给出在一定海面和海底反射系数、介质声吸收系数的条件下自噪声场相关系数与接收阵元间距的理论公式,并进行水平横向、水平纵向、垂直方向接收阵列的计算机仿真,从理论上分析散射自噪声场的空间特性。该理论研究为鱼雷自噪声的研究与半实物仿真提供了科学依据和有利支撑。     

船舶尾流气泡幕探测技术进展与应用

本文介绍并比较船舶尾流气泡幕的声学探测和光学探测的异同。以检测参量为主线,讨论光学探测中气泡对散射光强度、频率和偏振特性的影响,重点阐述基于脉冲回波、激光拉曼散射和光学成像等探测方式的应用原理、发展状况和存在的问题。以提高回波信号信噪比为目的,提出一种基于表面等离子激元的气泡尾流探测新思路,并进行相关模拟论证。气泡尾流光学探测法及其应用系统具有实时性好、灵敏度高、探测区域广等优点,在船舶监控、海洋水体污染检测和海洋生物环境监测等方面应用广泛。     

船舶尾流气泡幕探测技术进展与应用

本文介绍并比较船舶尾流气泡幕的声学探测和光学探测的异同。以检测参量为主线,讨论光学探测中气泡对散射光强度、频率和偏振特性的影响,重点阐述基于脉冲回波、激光拉曼散射和光学成像等探测方式的应用原理、发展状况和存在的问题。以提高回波信号信噪比为目的,提出一种基于表面等离子激元的气泡尾流探测新思路,并进行相关模拟论证。气泡尾流光学探测法及其应用系统具有实时性好、灵敏度高、探测区域广等优点,在船舶监控、海洋水体污染检测和海洋生物环境监测等方面应用广泛。     

舰船尾气流泡层散射函数分析

船舶航行过程中,螺旋桨对转动气压、航行震荡引起的水面波浪及空气流中的气体流动,这些综合因素会在船舶尾部形成大量的气泡。这些气泡的形成可能影响海水的温度并造成光学反射现象,对其气泡的形成原理及光学热学等特性分析可以更好的研究海洋环境变化。本文研究船舶尾气泡层的形成机理,利用Mik理论详细分析气泡的光学特性,对气泡散射函数进行数学模型分析,通过动态的数据处理过程模拟气泡层的变化,最后通过实验对理论分析进行验证。     

波斯湾海域基于经验关系的声散射受海面影响研究（英文）

In this paper, sound scattering from the sea surface in the Persian Gulf region is investigated. Chapman-Harris and Ogden-Erskine empirical relations coupled with perturbation theory are implemented. Based on the Ogden and Erskine's experiments, sound scattering from the sea surface has three different regimes in which two mechanisms of surface roughness and subsurface bubble clouds are involved. Ogden-Erskine's scattering relation which consists of perturbation theory and Chapman-Harris' s scattering terms are verified by the experimental data of Critical Sea Tests 7. Subsequently, wind speed in the Persian Gulf is provided based on three data bases of Arzanah station, ERA40, and PERGOS. Accordingly, surface scattering strength in the Persian Gulf region is calculated at different grazing angles, frequencies and provided wind speeds. Based on the resulted values of scattering strength, scattered intensity from the sea surface is also studied. These studies indicate that both scattering strength and scattered intensity generally increase as grazing angle, frequency and wind speed increase.     

喷射航行体辐射噪声机理分析

喷射航行体具有很高的速度,其辐射噪声主要含结构振动噪声和气泡脉动噪声。实测信号分析表明,低频分量基本无多普勒效应,以气泡脉动噪声为主;高频分量的空间位移速度大,以推进器壳体振动噪声为主。两类噪声对信号处理产生不同影响,表现在目标深度测量时效果各异,以气泡噪声的平滑效果为佳。     

单壳体潜艇在气泡脉动载荷作用下的响应规律研究

基于Geers与Hunter提出的自由场气泡脉动载荷计算方法,利用开尔文冲量法分析气泡自由场假设成立的条件,并将简单结构的计算结果同试验值进行对比,验证了所用算法的有效性。通过对简化的单壳体潜艇结构在不同气泡工况下响应的求解分析,得出如下结论:当气泡与边界距离大于其半径的3倍时,可忽略结构对气泡运动的影响;声固耦合法可有效求解结构在气泡脉动下的响应;在低频气泡脉动载荷激励下,结构的一阶及三阶垂向运动被激起,且以一阶运动为主;结构一阶垂向湿频率与气泡脉动的频率相差一定时,结构频率与其鞭状运动幅度呈负相关趋势;当气泡脉动频率与结构湿频率接近时,结构的响应出现峰值。     

水下爆炸压力时频分布的小波包分析

为了对舰船结构和设备的冲击环境进行研究,提出了基于小波包分析的水下爆炸压力时频分析方法.研究了短时非平稳水下爆炸压力实验测试信号的时频分布和能量分布规律,从水下爆炸压力时域信号中提取出冲击波,首次和二次气泡脉动压力信号,分析了它们在不同频带的能量分布规律.结果表明,基于小波包的时频分析方法可以提取水下爆炸压力不同时段的信号进行能量和频率分析,水下爆炸压力中以低频成分为主的气泡脉动压力产生的能量接近总能量的一半,是使安装频率为数十赫兹的舰船设备产生冲击振动的主要能源.     

A numerical investigation of bubble dynamics based on the potential-flow theory

1 Introduction1 In the past, people researched into the underwater bubble dynamics by combining the theoretical analysis and experimental study, however, theoretical analysis is limited to simple and regular cases and the repeatability and alterability of…     

水下目标几何声散射形态学特征的时频域盲分离（英文）

Separation of the components of rigid acoustic scattering by underwater objects is essential in obtaining the structural characteristics of such objects. To overcome the problem of rigid structures appearing to have the same spectral structure in the time domain, time-frequency Blind Source Separation(BSS) can be used in combination with image morphology to separate the rigid scattering components of different objects. Based on a highlight model, the separation of the rigid scattering structure of objects with time-frequency distribution is deduced. Using a morphological filter, different characteristics in a Wigner-Ville Distribution(WVD) observed for single auto term and cross terms can be simplified to remove any cross-term interference. By selecting time and frequency points of the auto terms signal, the accuracy of BSS can be improved. A simulation experimental has been used to analyze the feasibility of the new method, with changing the pulse width of the transmitted signal, the relative amplitude and the time delay parameter. And simulation results show that the new method can not only separate rigid scattering components, but can also separate the components when elastic scattering and rigid scattering exist at the same time. Experimental results confirm that the new method can be used in separating the rigid scattering structure of underwater objects.     

Blind source separation based on time–frequency morphological characteristics for rigid acoustic scattering by underwater objects

Separation of the components of rigid acoustic scattering by underwater objects is essential in obtaining the structural characteristics of such objects. To overcome the problem of rigid structures appearing to have the same spectral structure in the time domain, time–frequency Blind Source Separation (BSS) can be used in combination with image morphology to separate the rigid scattering components of different objects. Based on a highlight model, the separation of the rigid scattering structure of objects with time–frequency distribution is deduced. Using a morphological filter, different characteristics in a Wigner–Ville Distribution (WVD) observed for single auto term and cross terms can be simplified to remove any cross-term interference. By selecting time and frequency points of the auto terms signal, the accuracy of BSS can be improved. An experimental simulation has been used, with changes in the pulse width of the transmitted signal, the relative amplitude and the time delay parameter, in order to analyzing the feasibility of this new method. Simulation results show that the new method is not only able to separate rigid scattering components, but can also separate the components when elastic scattering and rigid scattering exist at the same time. Experimental results confirm that the new method can be used in separating the rigid scattering structure of underwater objects.     

水中目标回波脉冲包络起伏特征研究

水中目标散射声信号中蕴含了目标外形、结构、材质等物理属性信息,如何表征和提取这些属性信息一直是水中目标散射声信号分类与识别研究关注的焦点之一。为此,文章提出并研究了与水中目标属性信息相关联的散射声信号包络起伏特征,分析了该特征与目标外形、结构等物理属性间的内在关联及其形成机理,建立了相应的特征表征模型,并开展了理论仿真分析和模型实验验证研究。研究结果表明:体目标回波的脉冲包络起伏极值频率随入射声波的载频增加而增加,这体现了体目标的属性;Bench Mark模型的回波脉冲包络起伏频率与目标方位角密切相关,其中艏艉方向最大,正横方位最小。