粒子图像测速技术在拖曳水池中的应用

粒子图像测速技术（PIV）在大型拖曳水池中的应用面临着很多困难，诸如：水下激光片光照明、粒子图像捕捉、船舶流动的复杂程度、测量面积较大、粒子示踪，水下支架振动等。文章介绍了近十年来国内外PIV技术在拖曳水池中的应用和发展，对岸基式PIV和随车式PIV的优缺点做了比较与分析。还介绍了几个典型应用，即6：1椭球周围的速度及涡量分布的测量；不同尾附体连接形式的水下回转体伴流场测量；水面船首波流动结构的研究。文章还介绍了Iowa大学对拖曳水池PIV测量不确定度的评估研究。分析表明，国际水池PIV技术已经相当成熟并具备广阔的应用前景。     

Investigation of turbulent flows in a waterjet intake duct using stereoscopic PIV measurements

Stereoscopic particle image velocimetry measurements were made in a wind tunnel using a prototype waterjet model. The main wind tunnel provided the vehicle velocity and a secondary wind tunnel was set up as the waterjet propulsion model. Pressure distributions along the ramp and lip sides inside the duct were measured for three jet velocity to vehicle velocity ratios. Three-dimensional velocity fields were obtained at the intake entrance and the nozzle exit of the waterjet system. The flow into the duct was faster in the lip region than on the ramp side. Because of the variation in intake geometry from a rectangular to a circular section and because of the sudden curvature change on the lip side, a pair of counter-rotating vortices was observed in the mean velocity field at the nozzle exit. In addition, the turbulent kinetic energy correlated with the vortex pair was stronger on the lip side than in other areas. Dominant large-scale structures were extracted by using a snapshot proper orthogonal decomposition analysis. It was found that most of the turbulent kinetic energy was attributed to at least three vortices near the nozzle exit. This detailed three-dimensional velocity field will be useful for the verification of CFD simulations applied to the waterjet system.     

PIV基准流场的评估分析

PIV基准流场是规范PIV流场测试技术和校验流场测试数据的统一标准。文章通过分析PIV流场测试技术的发展及其基准流场技术的发展状况,对PIV基准流场建设方法进行初步研究。应用CFD方法初步评估了HTA及ITTC的建议模型,给出了基准模型周围流场结果,并与HTA提供的SPIV试验测试结果进行比较分析,对PIV基准流场的方案设计和不确定度分析进行了进一步思考。分析结果为模型标准与测试标准的建设提供了基础。     

分层流体中拖曳球体尾流及辐射内波试验研究

在大型分层流水池中采用 PIV 方法对跃变分层流体中小球尾流场进行了测量,获得了不同拖曳速度工况下跃层处的尾流及内波流场,对体效应稳态内波和尾流效应非稳态内波的特征有了形象直观的了解,获得了内波流场速度大小随内傅氏数的变化规律。     

PIV在柴油喷雾测试中的应用

介绍了可用于喷雾测试的几种激光技术的原理,讨论了PIV的测试原理及应用要求,并以TSI公司开发的PIV系统为例对DPIV系统的构成作了概括,最后对一些运用PIV进行喷雾测试的成果进行了简述。     

刚性摆动翼翼形与其尾部流场关系的实验研究

文章为研究刚性摆动翼翼形与其尾部流场关系,制定出一套完整的实验方案,并按实验要求制作了两种形状不同的刚性翼。通过PIV测量,实验记录了摆动翼尾部流场相关数据,并分析了翼形参数对其水动力性能的影响。该实验结果为进一步推导翼形参数、运动模式和推进效率三者间数学关系提供了实验数据支持。     

Visualization of periodic flows over a sunroof opening by using a phase-marked PIV measurement

Flows over cavity openings are known to be highly structured and periodic due to the strong sound pressures emitted by the cavities. This article is concerned with the measurement of flow fields over the sunroof opening of an SUV. Since the PIV system used in the present work is not capable of taking phase-locked velocity fields during the measurement stage, phase-marked PIV measurements are performed and the phase-locked velocity fields are retrieved during a post-processing stage. The new PIV measurement method is shown to yield fairly accurate results with a proper choice of a phase-bandwidth. By using the phase-marked PIV measurement method, the evolution of large-scale structures in shear flow over the sunroof opening as phase changes is revealed. The detached shear layer is shown to fluctuate and then form a discrete large vortex convecting and impinging on the rear roof edge of the SUV. The average convection velocity of the vortex is calculated to be 0.45 of the nominal free stream flow velocity. Flow fields are compared for four different cases of deflector protrusion and a case without a deflector. Installation of a deflector can significantly change the flow field. For a deflector that reduces the buffeting noise by more than 10 dB, it is shown that turbulent fluctuations are initiated by the deflector but do not grow in amplitude as they convect downstream. As the deflector protrusion is increased, the amount of flow under the deflector increases in general. The flow exiting from the channel formed by the deflector and an A-frame is shown to increase the thickness of the shear layer near the leading edge of the sunroof opening.     

近破波对直立建筑物的作用力及冲击流场研究

作用在直墙上的近破波对建筑物具有极大的破坏力,其作用机理非常复杂,至今尚无统一认识。利用粒子图像测速(PIV)技术与高精度压力传感器对直墙前的近破波流场和破波压力进行了同步测试,通过流场结构与破波压力的同步对比分析,探讨了近破波对直立建筑物的作用机理。     

基于多尺度的光流算法在PIV中的应用

提出一种基于多尺度分析的光流算法,此算法可以应用于PIV技术中。该方法针对数字图像建立整体光流模型,计算出全场象素点的速度矢量,可以修正原有的互相关算法计算所得结果中的错误矢量,能体现出互相关算法结果所体现不出的图像信息,对于PIV技术的发展有着重要的意义。文章介绍了光流模型的建立,并与传统互相关算法的结果进行了比较,验证了新方法得到的结果比原有算法所得到的结果有着明显的改进。