粒子成像测速

采用LaVision公司独特研发的抑制像素锁定偏差滤光片可以有效降低粒子成像测速实验中的本底偏差。同时还发展了一种降低像素锁定偏差的后处理滤波器。

采用德国LaVision公司的DaVis软件平台和四台高速相机，构建了时间分辨层析3D3C速度矢量场测量系统，对风洞中的空气流场进行了测量，并使用层析成像重建和三角测量的组合进行双帧粒子跟踪三维测速。

采用LaVision公司特色的以DaVis软件平台为基础构成的粒子成像测速（PIV）系统对气缸内流动结构在一段大范围的实际发动机转速区间内的速度场进行了测量和分析。

采用LaVision的显微粒子成像测速系统，对二尖瓣机械心脏瓣膜铰链区模型的铰链区的流场进行了测量和分析。

采用LaVision公司独有的可以应用到大体积空间的时间分辨层析粒子成像测速技术（Time-resolved Tomographyic PIV)对沙漠蝗虫在风洞环境下的复杂空气动力学行为进行了研究。

采用LaVision的sCMOS型CCD相机和200毫焦的PIV激光器，采用水下潜望镜形式拍照，采用荧光示踪粒子成像测速（PIV )方法跟踪掠过水体表面薄膜流场的涡核。

采用12台Lavision公司的Imager LX 2MP型PIV相机，在图像采集和控制软件平台DaVis构成了一套高空间分辨率体视层析3D3C速度场测量系统，并利用开系统实现了四脉冲层析粒子成像测速（Tomo-PIV）确定跨音速基流中的瞬时压力的研究。

可同时测量温度场分布和速度场分布。用于空气对流和热交换研究等应用领域。所采用的技术是使用既可以显示提供速度信息又可以提供温度信息的特种热敏感颗粒作为示踪粒子并应用粒子成像测速原理。成像数据的采集为高重复频率具有时间分辨本领。可以研究速度和温度的动态变化过程。

采用LaVision的DaVis 10.0图像采集和处理软件平台，加上一台Nd-YLF 激光器 (Continuum Terra-PIV, l = 527 nm)以及四台高速相机(Phantom Miro)构成了一套4D3C抖盒子流场测量系统。并利用这套系统进行了患者特异性脑动脉瘤血流动力学研究，分析比较了 体外体视粒子成像测速，计算流体动力学（CFD）和体内4D流动磁共振成像（MRI）等方法。

利用脉冲Nd:YAG激光器作光源，采用三台CMOS相机做成像器件，用组合的粒子图像PIV和跟踪测速PTV技术研究了砂砾动力学。

采用LaVision的Davis 8.3.0软件平台，IagerHS4M高速相机，以及LDY300高重频激光器，构成一套时间分辨粒子成像测速系统（TR-PIV),并利用该系统对低速非常规蒸汽流流场进行了实验测量和理论分析。

采用LaVision公司的双线平面激光诱导荧光（2-line-PLIF)和粒子成像以及粒子跟踪测速技术（PIV/PTV)，研究了水平管道中，油-水两种液体的流动特性。

采用LaVision公司由DaVis软件平台和ImagerPro型相机构成的粒子成像测速系统，对于水洞中的含有粗糙表面的流体的流场进行了测量并利用本征正交分解等数学工聚，对流动结构和水洞壁面表面粗糙度的相关性进行了实验研究。

采用新一代的抖盒子（‘Shake The Box’)这种利用粒子位置预判方法的高效精确的层析粒子跟踪测速（Tomo-PTV）方法，对空气，液体流动的时间分辨速度矢量场进行测量。可以得到拉格朗日视角的流场中示踪粒子随时间演化的精确粒子轨迹，并从粒子轨迹的演变过程，得到速度场和加速度场。并由此求出更多的流体力学参量，如压力场等。

采用英国Litron公司Nano系列200毫焦532nm双腔激光器，两台4百万像素相机从两个相对的方向，拍摄大视场和小视场的粒子图像。用LaVision的DaVis8.0数据采集和分析软件，分析用分形格栅生成的湍流场。

采用LaVision公司的Imager pro X 4 M相机构成层析流场测量系统，对稀疏重构的粒子跟踪，和高浓度粒子的层析PIV测量进行了比较分析。

采用LaVision公司DaVis8.4图像采集和分析软件平台，可编程时间控制器PTU和高速相机，红外相机，构成一套可以用双色法，红外法测温，以及粒子图像测速系统，测量了水池沸腾过程的温度和速度场。

动态成像粒子分析（DIPA）系统为您提供FDA推荐的蛋白质制剂中颗粒的深入表征。 在探索使用此原理的仪器时，应考虑以下五个重要特征。图像质量适用性仪器的灵敏度样品量的要求易于分析和数据处理

在过去几十年中，已经发展出了多种基于粒子图像的体积流场测量技术，这些技术已经在流体力学的各种实验应用中展示了它们量化评估非定常流动性质的潜力。在这篇综述中，我们专注于3D基于粒子的测量的物理特性和环境，以及可以用于提高重建精度、空间和时间分辨率以及完整性的知识。我们关注的自然候选者是3D拉格朗日粒子跟踪（LPT），它允许在所研究的体积中确定位置、速度和加速度以及大量单个粒子轨迹。过去十年中，密集的3D LPT技术“Shake-The-Box”的出现开辟了更多的可能性，通过提供用于使用Navier-Stokes约束的强大数据同化技术的输入数据来表征非定常流动。因此，可以获得高分辨率的拉格朗日和欧拉数据，包括嵌入时间分辨的3D速度和压力场中的长粒子轨迹。

PIV systems rely on a combination of seed particles, laser light intensity, and camerapositioning to collected velocity data. Careful attention is needed when selecting the ap-propriate setup conguration for PIV systems. This paper focuses on several areas forimprovement in PIV data collection for a compressible turbulent boundary layer studyon a at plate using MVG's. The topics include determining the seed particle surfacepreparation for a at plate, and PIV system conguration.

This paper describes the principles of anovel 3D PIV system based on the illumination,recording and reconstruction of tracer particles withina 3D measurement volume. The technique makes useof several simultaneous views of the illuminated particlesand their 3D reconstruction as a light intensitydistribution by means of optical tomography. Thetechnique is therefore referred to as tomographicparticle image velocimetry (tomographic-PIV). Thereconstruction is performed with the MART algorithm,yielding a 3D array of light intensity discretizedover voxels. The reconstructed tomogram pair is thenanalyzed by means of 3D cross-correlation with aniterative multigrid volume deformation technique,returning the three-component velocity vector distributionover the measurement volume. The principlesand details of the tomographic algorithm are discussedand a parametric study is carried out by means of acomputer-simulated tomographic-PIV procedure. Thestudy focuses on the accuracy of the light intensity fieldreconstruction process. The simulation also identifiesthe most important parameters governing the experimentalmethod and the tomographic algorithmparameters, showing their effect on the reconstructionaccuracy. A computer simulated experiment of a 3Dparticle motion field describing a vortex ring demonstratesthe capability and potential of the proposedsystem with four cameras. The capability of the techniquein real experimental conditions is assessed withthe measurement of the turbulent flow in the nearwake of a circular cylinder at Reynolds 2,700.

The emission of oxides of nitrogen, or NOx, by aircraft is an international concern. NOxcontributes to smog in the lower atmosphere and destroys ozone in the stratosphere. To reduce NOxand other harmful emissions, NASA has developed Multipoint Lean-Direct Injection (MP-LDI). To determine the effectiveness of MP-LDI and its potential for future commercial use, particle image velocimetry (PIV) obtains velocity data which is important for setting the inlet and boundary conditions needed for validating computational fluid dynamics codes such as the National Combustor Code (NCC).

We report particle image velocimetry measurements of the collision of a vortex ring with a heatedwall kept at constant temperature. We consider the case when both the vortex ring and the thermalboundary layer generated by the vertical heated wall are stable and laminar prior to any interaction.The impingement process can be divided into two parts. sid A ring-driven stage, where the vortexring grows in diameter while approaching the wall and therefore it sweeps progressively anincreased surface on the wall. siid A boundary layer-driven stage, where the vortex ring movesupward due to the thermal convective motion generated by the heated wall. In some cases, thehead-on collision triggers the ring’s azimuthal instability as revealed by the formation of vorticalstructures arranged on a wavy starlike pattern and confirmed by flow visualizations. A singlecollision generates important velocity gradients and shear stresses along the wall accompanied withthe creation of local vorticity normal to the vertical heated wall. Peak wall shear stresses occur nearthe point of impact of the vortex ring core.

采用LaVision公司的粒子成像测速系统(PIV)和粒子跟踪测速系统(PTV)对无反应条件下氧煤燃烧室中颗粒流动的速度场进行了实验测量研究。

The objective of this project is to study the aerodynamics around a birdlike airfoil. Thevariables to investigate are the turbulent shear stress and the pressure distribution. Withthis aim, two experiments were carried out in the LNB wind tunnel.The seagull hand pinion inspired the SG04 birdlike airfoil considered for this work. Aflapping flight motion apparatus was used to force this wing heaving and pitching.First, an experiment to capture the boundary layer and determine the shear stress wasdone. Therefore, very accurate measurements with stereoscopic Particle ImageVelocimetry technique were required. This exercise was performed with a flexible andnon-flexible SG04 wing.Moreover, with the same method, a second experiment tried to capture a larger flow fieldaround the whole flexible flapping SG04 airfoil, in order to determine the pressuredistribution.To begin with, a theoretical background highlighting the most important features of movingairfoils and Particle Image Velocimetry is presented. The experimental setup, recording,data processing and results of both experiments conclude the second part of this work.

FlowMaster系统系统的PIV软件包在DaVis硬件控制平台上增加了对不同应不同应不同应用定制的瞬态速度场测量系量系统。统。它提供提供的先进算法和为用户精心设计的工具包使得从使得从使得从图像文件到速度矢量场以及量场以及量场以及量场以及其他导出标量场的操作过程得心应手。

The aim of this work was to understand the physical requirements as well as to developmethodology required to employ Time Resolved Digital Particle Image Velocimetry(TRDPIV) for measuring high speed, high magnification, near wall flow fields. Previousattempts to perform measurements such as this have been unsuccessful because ofboth limitations in equipment as well as proper methodology for processing of the data.This work addresses those issues and successfully demonstrates a test inside of atransonic turbine cascade as well as a high speed high magnification wall jet.From previous studies it was established that flow tracer delivery is not a trivial task in ahigh speed high back pressure environment. Any TRDPIV measurement requiresuniform spatial seeding density, but time-resolved measurements require uniformtemporal seeding density as well. To this end, a high pressure particle generator wasdeveloped. This advancement enhanced current capability beyond what was previouslyattainable. Unfortunately, this was not sufficient to resolve the issue of seeding alltogether, and an advanced data reconstruction methodology was developed toreconstruct areas of the flow field that where lost do to inhomogeneous seeding. Thisreconstruction methodology, based on Proper Orthogonal Decomposition (POD), hasbeen shown to produce errors in corrected velocities below tradition spatial techniquesalone. The combination of both particle generator and reconstruction methodology wasinstrumental for successfully acquiring TRDPIV measurements in a high speed highpressure environment such as a transonic wind tunnel facility.This work also investigates the development of a turbulent wall jet.

Flow past a cylinder in an unbound medium gives rise toself-sustained, limit cycle oscillations involving formationof a regular, periodically alternating Karman vortex street.However, little attention has been paid to the effect of anadjacent free surface on the development of the Karmanvortices and possible generation of new classes of the nearwakestructure[1], see Figure 1. The technique of ParticleImage Velocimetry (PIV) is a useful tool to this flow,considering that it is unsteady and multi-scale in nature.

Thermoacoustic refrigeration systems generate cooling power from a high-amplitude acousticstanding wave. There has recently been a growing interest in this technology because of its simple androbust architecture and its use of environmentally safe gases. With the prospect of commercialization,it is necessary to enhance the efficiency of thermoacoustic cooling systems and more particularly ofsome of their components such as the heat exchangers. The characterization of the flow field at theend of the stack plates is a crucial step for the understanding and optimization of heat transfer betweenthe stack and the heat exchangers. In this study, a specific Particle Image Velocimetry measurement(PIV) isperformed inside a thermoacoustic refrigerator. Acoustic velocity is measured using synchronizationand phase-averaging. The measurement method is validated inside a void resonator by successfullycomparing experimental data with an acoustic plane wave model. Velocity is measured inside theoscillating boundary layers, between the plates of the stack, and compared to a linear model. Theflow behind the stack is characterized, and it shows the generation of symmetric pairs of counterrotatingvortices at the end of the stack plates at low acoustic pressure level. As the acoustic pressurelevel increases, detachment of the vortices and symmetry breaking are observed.

• PIV is a fluid measurement technique that is used to determine the average displacement of a group of particles.• PIV offers advantages over particle tracking by enabling the rapid reconstruction of spatially resolved two-and three-dimensionalvelocity fields.• PIV has facilitated detailed measurements of a wide variety of phenomena in complex (dusty) plasmas from particle transport toDAW/DDW to thermal properties.• New developments:o Detailed benchmarking of PIV against simulationso Spatially resolved stereo-PIVo Tomographic PIVo Time-resolved PIV