体积噪声场和界面噪声场中声矢量传感器线阵阵增益分析

Acoustic vector sensor consists of pressure and particle velocity sensors,which measure the three-dimensional acoustic particle velocity,as well as the pressure at one location at the same time.By preserving the amplitude and phase information of the pressure and particle velocity,they possess a number of advantages over traditional scalar sensors.Signal-to-noise ratio (SNR) gain (which is often called array gain) is one of such advantages and is always interested by all of us.But it is not unchangeable if the spatial correlation of the noise field varies.Much more important,it is difficult to be given if the noise becomes complex.In this paper,spatial correlation of the vector field of isotropic volume-noise and surface-generated noise has been introduced briefly.Based on the results,the combined SNR output of a vector linear array is investigated and the maximum gain is given in the specified noise.Computer simulation shows that the output of one array in the same noise is not the same in different gestures.And then we find the best gesture through SNR calculation and obtain the biggest gain,which has important meaning to guide how to deploy an array in practice.We also should use the array with respect to the characteristics of the real ambient noise,especially in anisotropic noise field.     

宽带声矢量场的表征(英文)

Compared to a scalar pressure sensor, a vector sensor can provide a higher signal-to-noise ratio (SNR) signal and more detailed information on the sound field. Study on vector sensors and their applications have become a hot topic. Research on the representation of a vector field is highly relevant for extending the scope of vector sensor technology. This paper discusses the range-frequency distribution of the vector field due to a broadband acoustic source moving in a shallow-water waveguide as the self noise of a surface ship, and the vector extension of the waveguide impulse response measured over a limited frequency range using an active source of known waveform. From theory analysis and numerical simulation, the range-frequency representation of a vector field exhibits an interference structure qualitatively similar to that of the corresponding pressure field but, being quantitatively different, provides additional information on the waveguide, especially through the vertical component. For the range-frequency representation, physical quantities that can better exhibit the interference characteristics of the waveguide are the products of pressure and particle velocity and of the pressure and pressure gradient. An image processing method to effectively detect and isolate the individual striations from an interference structure was reviewed briefly. The representation of the vector impulse response was discussed according to two different measurement systems, also known as particle velocity and pressure gradient. The vector impulse response representation can not only provide additional information from pressure only but even more than that of the range-frequency representation.     

表面噪声矢量场空间相关特性射线声学建模(英文)

Spatial correlation of sound pressure and particle velocity of the surface noise in horizontally stratified media was demonstrated,with directional noise sources uniformly distributed on the ocean surface.In the evaluation of particle velocity,plane wave approximation was applied to each incident ray.Due to the equivalence of the sound source correlation property and its directivity,solutions for the spatial correlation of the field were transformed into the integration of the coherent function generated by a single directional source.As a typical horizontally stratified media,surface noise in a perfect waveguide was investigated.Correlation coefficients given by normal mode and geometric models show satisfactory agreement.Also,the normalized covariance between sound pressure and the vertical component of particle velocity is proportional to acoustic absorption coefficient,while that of the surface noise in semi-infinitely homogeneous space is zero.     

Monolithic coupling of the pressure and rigid body motion equations in computational marine hydrodynamics

In Fluid Structure Interaction(FSI) problems encountered in marine hydrodynamics, the pressure field and the velocity of the rigid body are tightly coupled. This coupling is traditionally resolved in a partitioned manner by solving the rigid body motion equations once per nonlinear correction loop, updating the position of the body and solving the fluid flow equations in the new configuration. The partitioned approach requires a large number of nonlinear iteration loops per time–step. In order to enhance the coupling, a monolithic approach is proposed in Finite Volume(FV) framework,where the pressure equation and the rigid body motion equations are solved in a single linear system. The coupling is resolved by solving the rigid body motion equations once per linear solver iteration of the pressure equation, where updated pressure field is used to calculate new forces acting on the body, and by introducing the updated rigid body boundary velocity in to the pressure equation. In this paper the monolithic coupling is validated on a simple 2D heave decay case. Additionally, the method is compared to the traditional partitioned approach(i.e. "strongly coupled" approach) in terms of computational efficiency and accuracy. The comparison is performed on a seakeeping case in regular head waves, and it shows that the monolithic approach achieves similar accuracy with fewer nonlinear correctors per time–step. Hence, significant savings in computational time can be achieved while retaining the same level of accuracy.     

深海矢量噪声场声传播特性研究

矢量声压振速联合处理是建立在信号的声压和质点振速相位基础上,海洋环境边界对声传播的影响将改变矢量声场声压和质点振速的幅度和相位特性。文章根据南海环境条件和水下目标辐射噪声测量采用矢量简正波理论估算海面非相干偶极子噪声源和水下点声源矢量场的幅度和相位随深度的变化,并对矢量水听器测量系统获取的南海典型深度上的背景噪声数据进行了分析。结果表明:深海背景噪声声压谱级在500 Hz以下基本上不随深度变化,在500 Hz-3 kHz频段浅深度背景噪声声压谱级略高于较深深度的背景噪声声压谱级;背景噪声的垂直质点振速谱级要小于声压和水平质点振速谱级。     

水锤冲击时管路系统流固耦合响应的特征线分析方法研究

本文以Wiggert 和Hatfield[3]的特征线分析方法为基础,研究管路在水锤冲击下考虑泊松耦合时流体和结构的瞬态响应.推导了分别对应于管中流体压缩波和管壁中纵波的特征关系式和相容方程,并联合采用空间插值和显式时间插值进行数值求解.针对经典的水锤压力冲击的算例,将边界和初始条件离散化,编制了MATLAB程序进行计算,获得管道中流体压力和流速及轴向应力和振动速度的时程曲线,计算结果与理论分析相当吻合.根据计算结果,提出了对于实际管路设计和水锤防护有益的结论.鉴于特征线法本身的优势,有望在管路系统抗冲击设计分析和防护研究中得到进一步的应用.     

基于空间域数据拟合的声矢量阵多目标分辨算法研究

为了提高矢量传感器阵列的方位估计性能,提出了一种基于空间域数据拟合的矢量阵多目标分辨算法,通过利用已知的空间域数据信息,构造出新的声压与振速的接收数据协方差矩阵,在多目标分辨能力上对经典MUSIC算法予以改进。理论分析和计算机仿真表明,在各向同性噪声场中,新算法在提高多目标分辨能力方面比传统方法更有效。     

不规则波对平板冲击作用数值模拟研究

文章采用数值模拟方法,建立了基于FLUENT软件的二维不规则波浪数值模型,探讨了波浪对水平板结构的作用机理.模型中采用RANS方程和标准k-ε方程,采用VOF方法重建自由液面.通过数值模拟复演了波浪冲击水平板结构的过程,将数值模拟结果与实验数据进行比较,验证了模型的可靠性.经过计算和分析,研究了波浪冲击平板过程中的冲击压力和流场特性,得到了冲击压力和流场的分布规律.分析了波陡,净空及板宽等参数对冲击压力和流场的影响.最后,给出了波浪冲击压力与相应水质点垂直速度间的统计关系,并对河海大学原有冲击压力的计算公式进行了改进,提出了新的冲击压力公式.研究结果表明:冲击压力峰值与相应的水质点垂直速度的平方成正比,修正后的冲击压力公式更为合理、可行.论文工作将对准确预测冲击载荷,掌握更多的冲击机理具有重要意义.     

基于DES方法的三维圆柱受迫振动数值模拟

基于OpenFOAM平台对雷诺数3900下的三维固定圆柱绕流和雷诺数30000下的三维圆柱受迫振动进行数值模拟,对湍流的模拟采用SA-DDES离散涡模型.针对三维圆柱绕流问题,采用PISO算法耦合求解速度-压力场,对圆柱绕流的基础参数如St数、平均阻力系数和平均升力系数等与试验进行了比较,结果吻合良好.针对三维圆柱受迫振动问题,采用PIMPLE算法耦合求解速度-压力场,对不同频率下振幅比为0.3的阻力系数、尾涡形态进行了计算,阻力平均系数与实验值相比吻合较好.     

强磁场环境下磁流体数值模拟系统开发与应用

基于强磁场环境下聚变堆包层中液态金属流体的基本物理过程，采用三阶龙格库塔四步投影法求解N_S方程，相容守恒格式计算电流和电势，建立符合该现象的磁流体动力学方程组，设计开发数值模拟系统。由于该文构造的离散模型具有很好的守恒特性和精确度，数值模拟结果表明该系统对研究磁流体MHD效应，揭示磁流体流动压降、流速分布，对提高磁流体动力学系统设计效率及工程应用具有很好的参考价值。     

A characteristic analysis of the dynamic stability of underwater shell-like lattice marine structures

The deformation mechanisms of submerged shell-like lattice marine structures composed of circular arches and membrane are, in principle, of a non-conservative nature as circulatory load system, because the working force is of the follower type, namely hydrostatic pressure. This paper presents the governing equations for the finite deformations of shell-like lattice structures, defined with monoclinic particle coordinates. The governing equations have been developed using the method of disturbed small motions to clarify the stability problem of shell-like lattice structures. Numerical results show that the complex peninsular shaped instability regions are in the excitation force field for arch-lattices under certain loading conditions, and their stability collapses suddenly past a threshold point of dynamic equilibrium, from a heteronomous state to an autonomous state of self-sustained motions. The concept of the existence of an overall dynamic stability threshold for a shell-like lattice underwater structure is presented here.     

单矢量传感器目标定向原理

声矢量传感器可以同时获取声波场的声压和振速信息.因振速是一个矢量,因而单个矢量传感器就能够提供声场的方位信息,为小尺度声传感器的设计提供了可能.论文首先对单矢量传感器目标定向的原理进行了研究,在单频信号处理的基础上扩展到实际中的宽带随机信号的处理,并进行了仿真分析研究.     

导边与随边设计对喷水推进泵性能的影响

采用相同的叶片轴面流线载荷分布和叶轮出口环量分布规律,改变导边与随边位置设计出多个喷水推进泵叶轮。基于雷诺时均的N-S方程、SST湍流模型和多重参考坐标系对叶轮内流场进行数值模拟,结果表明：导边向进口适度延伸可减小叶片进口边的载荷,利于提高空化性能,但效率有所降低;随边倾斜参数与叶轮出口的轴面速度分布和叶片表面的压力分布特性关联。     

船用离心泵内部流场数值分析和性能预测

通过对船用离心泵内流场三维不可压湍进行数值模拟，揭示了泵内流道的压力及速度分布规律，根据泵内流道的压力及速度分布规律，对泵进行水力优化设计，同时对船用离心泵的性能进行预测．     

深槽水域垂向二维水沙运动数值模拟

采用网格堵塞技术实现实际地形的模拟,采用有限体积法离散方程,采用SIMPLER算法求解耦合的速度场和压力场,并建立了沿宽度积分的垂向二维水流泥沙数学模型。将计算结果和试验资料进行对比,结果吻合良好。     

复合材料螺旋桨尾流场的数值模拟

为了分析复合材料螺旋桨的变形对桨后尾流场分布的影响,利用商业软件FLUENT和ANSYS有限元建立了一种流固耦合方法,基于此方法分析了桨叶变形对螺旋桨压力分布以及尾流场分布的影响。研究结果表明,变形后桨叶两侧压差增大;在螺旋桨尾流场中,变形对各速度分量周向分布的影响随半径增大而增大;在0.9R(R为螺旋桨半径)处,切向速度在变形后减小约30%,轴向诱导速度减小约20%,径向速度增值在0.1m/s内。变形后轴向速度低速度区域增大,径向速度正速度区域增大,叶根处切向速度增大,叶稍处切向速度减小。     

基于SPH法的径向滑动轴承动压润滑研究

为了研究润滑油膜的粒子性对流体动压润滑的影响,该文提出利用SPH方法（光滑粒子动力学方法）分析径向滑动轴承流体动压润滑,模拟结果通过计算流体动力学（CFD）软件FLUENT分析结果和润滑理论提供的解析解进行了比较验证。同CFD 法一样,SPH法的压力分布结果揭示了润滑理论忽略掉的流体惯性效应。三种方法速度场分析结果略有不同。因此,SPH模型由于反映了流体的粒子性,可成为求解滑动轴承中的复杂流体润滑问题的有效工具。     

带自由面流体运动的拉格朗日有限元分析

介绍了拉格朗日描述下的非定常不可压缩带自由面流体运动的有限元分析.在时间积分中采用速度修正法,采用速度修正分步法不仅可以让速度和压力均采用同阶插值函数,而且可以使算法变得更简单.用四边形单元对所求区域加以划分,并借助于Galerkin加权余量法导出相应的有限元方程组.通过实例计算,阐明了用该方法来分析带自由面流体运动的有效性及其实用性.     

汽车空调箱内空气流动的数值模拟研究

建立了汽车空调箱的数学模型,与换热器的单体吹风实验结合,采用多孔介质模型计算了空气在蒸发器与暖风芯体间的压力降。通过分析换热器内部速度场、压力场,揭示了空气在空调箱内的流动特性。结果表明：由于蒸发器迎风面积较大,蒸发器侧的压力损失不高,而在暖风芯体处,由于通道扩张不充分,芯体处的速度场不均匀,流体在箱体边缘发生了回流,降低了芯体的换热效能。在出口处,存在较强涡流,是空调箱阻力的主要来源。     

舰船用钢的抗弹道冲击性能研究进展

对我国舰船用钢抗弹道冲击性能的研究情况及主要成果进行了总结和评述.概括了舰船在战争中所面临的主要威胁,描述了我国舰船用钢的发展历程,论述了材料的动态本构模型的重要性,提出了获取手段和使用要求.回顾了重要的侵彻深度、弹道极限和剩余速度的经验公式,并指出了它们的局限性和使用方法.详细研究了靶板的破坏模式、特点及尖头弹和钝头弹在侵彻机理上的差异,并提出了建立模型的具体步骤.总结了试验研究的主要方向,指出了其重要意义;分析了各种研究方法间的相互联系.最终提出了在研究舰船用钢的抗侵彻性能和设计舰船装甲防护方案时的五步法.