双向分布水翼周围有势流动时的耗散自由表面解

为浸没于自由表面下部的2维水翼,建立水翼周围作耗散有势流动时的二次积分方程.假设自由表面具有能量的耗散,也就是阻尼的来源.根据耗散Green函数的无旋性近似和水翼表面的双向分布,提出了双向的面元法( doublet panel method).数值计算后得到的结果,与分析解和已有实验数据均吻合得很好.     

基于偏振模式转换的声光陀螺研究

提出一种基于偏振模式转换的声光陀螺,分析其原理与结构并对该陀螺进行实验测试。静态测试结果表明,当声光作用长度为15mm,声表面波输入功率为100mW,频率为168.201MHz时,偏振模式转化效率为80.02%。在偏置条件下进行旋转测试,得到输出电压随陀螺转速呈线性变化的曲线,其灵敏度约为1mV/[(°)/s]。偏振型声光陀螺保留声表面波陀螺体积小、成本低等优点,而在灵敏度上有大幅提高。     

界面剪切力作用下波状液膜流的水动力稳定性

液膜流的水动力稳定性作为保障其高效传热传质性能的重要因素之一,受多种因素的制约和影响. 当气液界面处存在因气流流动而产生剪切力作用时,剪切力将通过改变界面处的边界条件,从而影响液膜流动的稳定性. 基于边界层理论,采用积分法建立了剪切力作用下降液膜表面波演化方程,分析了界面剪切力对水动力稳定性的影响. 研究表明,正向剪切力为不稳定性因素,反向剪切力在较小雷诺数时为不稳定因素,在大雷诺数时为稳定性因素;正向剪切力使临界波数和临界波速增大,反向剪切力使其减小;剪切力对临界波速的影响在不同雷诺数下也有所不同.      

一种新型基于两通道声表面波器件的全光纤调制器

研究了多通道声表面波与光纤中传播的光导波相互作用,推导出其相应的耦合模方程.研制了一种两通道声表面波全光纤声光调制器并进行了实验,理论分析与实验结果相符合.     

声表面波谐振器频率-温度行为分析

声表面波（SAW）器件以其优良的性能广泛应用于雷达、通讯和日常用品等领域。然而,随着器件工作频率的不断升高,温度对器件频率稳定性的影响也越来越严重。因此,研究声表面波器件的温度效应,并在变温情况下保持SAW器件的频率稳定性至关重要。本文采用增量型的拉格朗日方程分析受温度影响的声表面波频率漂移问题。用频率-温度系数（TCF）作为评价频率-温度行为的标准。设计了一个具有温度补偿层的双层SAW谐振器模型,降低了器件的频率-温度系数。通过尺寸优化,LiNbO3-AlN结构的SAW谐振器在25℃（参考温度）下的频率温度系数TCF接近0ppm/℃。SAW谐振器的波长为4μm,谐振频率为1214.9MHz。     

平面液体层碎裂过程实验研究

小宽厚比喷嘴喷射出的平面水膜进入静止空气中,在不同气流流速环境下对水膜碎裂过程进行了实验研究。结果表明,静止空气中的水膜表面波呈现对称波形,射流的碎裂长度随雷诺数的增大而增大,喷射压力对射流碎裂长度没有直接影响。空气助力作用使平面射流表面波的上、下气液交界面出现相位差。水膜的碎裂长度随空气助力气流速度的增大而减小;空气助力对于低雷诺数水膜射流具有很强的促进碎裂作用,所以会极大地改善低雷诺数射流的一次雾化效果。随着水流雷诺数的提高,空气助力作用对水膜碎裂长度的影响大为减弱;即使在高速助力空气的作用下,水膜仍长期保持较稳定的射流流态,没有出现明显的水膜撕裂现象。说明在小宽厚比喷嘴的瑞利(Rayleigh)模式射流中,高雷诺数射流是水膜的稳定因素。与气液流速比、气流马赫数等无量纲参数相比,液体喷射的雷诺数是射流碎裂的主要影响因素。     

带温度补偿、低g-振动灵敏度的小型声表面波微波源

描述了一种采用模拟温度补偿技术用于声表面波微波源 ,其工作频率为 2 .2 GHz,器件在工作温度为 - 35℃～ + 5 5℃范围内 ,频率变化从两百多 ppm改善到小于± 30 ppm之内 ,使器件在90℃的温度范围内频率随温度变化的性能改善约 10倍。其 g-振动灵敏度小于 10 - 1 0 /g。尺寸仅6 0 m m× 2 5 mm× 15 mm。     

带温度补偿,低g—振动灵敏度的小型声表面波微波源

描述了一种采用模拟温度补偿技术用于声表面波微波源 ,其工作频率为 2 .2 GHz,器件在工作温度为 - 35℃～ + 5 5℃范围内 ,频率变化从两百多 ppm改善到小于± 30 ppm之内 ,使器件在90℃的温度范围内频率随温度变化的性能改善约 10倍。其 g-振动灵敏度小于 10 - 1 0 /g。尺寸仅6 0 m m× 2 5 mm× 15 mm。     

A set of Boussinesq-type equations for interfacial internal waves in two-layer stratified fluid

Many new forms of Boussinesq-type equations have been developed to extend the range of applicability of the classical Boussinesq equations to deeper water in the study of the surface waves. One approach was used by Nwogu (1993. J. Wtrw. Port Coastal and Oc. Eng. 119, 618--638) to improve the linear dispersion characteristics of the classical Boussinesq equations by using the velocity at an arbitrary level as the velocity variable in derived equations and obtain a new form of Boussinesq-type equations, in which the dispersion property can be optimized by choosing the velocity variable at an adequate level. In this paper, a set of Boussinesq-type equations describing the motions of the interfacial waves propagating alone the interface between two homogeneous incompressible and inviscid fluids of different densities with a free surface and a variable water depth were derived using a method similar to that used by Nwogu (1993. J. Wtrw. Port Coastal and Oc. Eng. 119, 618--638) for surface waves. The equations were expressed in terms of the displacements of free surface and density-interface, and the velocity vectors at arbitrary vertical locations in the upper layer and the lower layer (or depth-averaged velocity vector across each layer) of a two-layer fluid. As expected, the equations derived in the present work include as special cases those obtained by Nwogu (1993, J. Wtrw. Port Coastal and Oc. Eng. 119, 618-638) and Peregrine (1967, J. Fluid Mech. 27, 815-827) for surface waves when the density of the upper fluid is taken as zero.     

Vibration reduction of floating elastic plates in surface waves

Based on dynamical theories of water waves and dynamics of Mindlin thick plates,the investigation of the wave-induced responses and the vibration reduction of an elastic floating plate are presented using the Wiener-Hopf technique.Without regard to the case of elastic connector,the calculated results obtained by the present method are in good agreement with those from the literature and the experiment.It can be shown that the present method is valid.Relations between the spring stiffness to be used to connect the sea bottom and the floating plate and the parameters of wave-induced responses of floating plates are investigated using the present method.Therefore, these results can be used as theoretical bases for the design stage of super floating platform systems.