Robust airfoil optimization based on improved particle swarm optimization method

A robust airfoil optimization platform is constructed based on the modified particle swarm optimization method (i.e., the second-order oscillating particle swarm method), which consists of an efficient optimization algorithm, a precise aerodynamic analysis program, a high accuracy surrogate model, and a classical airfoil parametric method. There are two improvements for the modified particle swarm method compared with the standard particle swarm method. First, the particle velocity is represented by the combination of the particle position and the variation of position, which makes the particle swarm algorithm a second-order precision method with respect to the particle position. Second, for the sake of adding diversity to the swarm and enlarging the parameter searching domain to improve the global convergence performance of the algorithm, an oscillating term is introduced to the update formula of the particle velocity. At last, taking two airfoils as examples, the aerodynamic shapes are optimized on this optimization platform. It is shown from the optimization results that the aerodynamic characteristic of the airfoils is greatly improved in a broad design range.     

基于拓扑优化的声学结构材料分布设计

本文针对结构的声学设计问题进行研究,通过优化两种不同的材料在结构设计域内的拓扑分 布来最小化谐振结构所产生的声场中指定参考面/参考域内的声压。在研究中假定结构为线弹性小变 形结构,材料阻尼为Rayleigh阻尼,声学介质为无粘、可压缩、小扰动流体。对结构响应采用有限 元格式进行计算,对声场采用基于Helmholtz积分的边界元格式进行计算,由于声场在无穷远自由边 界的无反射条件在边界积分中能自动得到满足,该格式特别适合于具有开放边界的声场计算。建立 了结构有限元-声场边界元格式的耦合系统拓扑优化模型,导出了耦合系统敏感度分析的一般格式及 伴随格式。数值算例验证了所提出的结构-声学耦合系统优化方法的有效性和可靠性,并揭示了基于 声学准则的拓扑优化结果的有关特性 关键词边界积分,结构声学耦合系统,拓扑优化,敏感度分析,伴随方法     

Aerodynamics of indirect thrust measurement by the impulse method

The aerodynamic aspects of indirect thrust measurement by the impulse method have been studied both experimentally and numerically. The underlying basic aerodynamic principle is outlined, the phenomena in subsonic, supersonic and arc-heated jets are explored, and factors affecting the accuracy of the method are studied and discussed. Results show that the impulse method is reliable for indirect thrust measurement if certain basic requirements are met, and a simple guideline for its proper application is given.     

Investigation on nonlinear thermo-acoustic characteristics of Rijke tube

Based on the energy conservation relationship,nonlinear thermo-acoustic effects of Rijke tube including instability range,saturation processes and higher harmonics modes were investigated.With coupling between the external flow and the inner space of a Rijke tube, the acoustic characteristics of self-excited oscillation were simulated.The experimental study was also carried out and the results were compared with those from simulation.The nonlinear factors which distort the acoustic waveform distortion were analyzed.From the results,it is seen that varying size of the nozzle outlet changes the acoustic impedance in the boundary, and leads to reduction of the nonlinear effects.The results show that the modes of self-excited oscillation could be influenced by the position of higher harmonics.In the large amplitude oscillation,the distortion of pressure wave within Rijke tube could be induced by the acoustic losses due to vortices on nozzle.It is found that the waveform distortion could be avoided by the shrinkage of nozzle.     

柱状分层固体媒质的声散射

本文评述了各向同性和横向各向同性柱状分层固体声散射理论和实验研究进展 ,介绍了描述圆柱状界面薄层特性的弹簧模型 ,也讨论了该领域中有待进一步研究的一些问题。     

《应用声学》征稿简则

《应用声学》是由中国科学院主管,中国科学院声学研究所主办,中国声学学会、《应用声学》编辑委员会编辑出版的学术刊物。1982年创刊,双月刊,国内外公开发行。办刊的宗旨是繁荣应用声学事业,促进新     

风速对空气源热泵翅片管换热器结霜特性影响

针对风速对空气源热泵翅片管室外换热器结霜特性的影响进行了实验研究.实验结果表明,结霜量随风速的增加不是成线形增长,在风速为1.3m/s时结霜量最小.霜层厚度随着风速的增加反而减小,而翅片管换热器的最大换热量随着风速的增加而增加.     

水中空气隔层衰减冲击波性能研究

 根据鱼雷对舰船毁伤的特点,建立了多介质水下爆炸数值模型,提出了交界面处理及广义光滑长度计算方法,编制了多介质水下爆炸计算程序,并对水下爆炸空气隔层衰减冲击波的性能进行了定量分析。结果表明：无论是接触爆炸还是非接触爆炸,空气隔层均可有效衰减冲击波,并且接触爆炸中空气隔层衰减冲击波的效果更好,最大可使冲击压力峰值降低约55%;空气隔层厚度与爆炸厚度之比为1时便可达到较好的衰减冲击波效果,继续增加空气隔层厚度对衰减冲击波效果影响不大。研究结果可为舰船结构防护及防雷舱的结构设计提供参考。     

《声学学报》征稿简则

一、声学学报是中国科学院声学研究所主办,中国声学学会、声学学报编辑委员会编辑出版的学术性刊物,刊载全国具有创造性的声学研究论文、实验性论文和重要应用性论文(包括实验工作、理论和应用研究、仪器研制)。已在公开刊物上发表过或同时投向其他学术刊物的稿件不收。重要成果或部分重要成果可写成快报以便提前发表。评述性的论文以编委会约定者为限。二、凡投送本刊的文章,作者(们)应保证该文不违反中华人民共和国法律,尤其是保密法和著作权法;如违法,责任自负。