Imager SX PIV相机

利用LaVision公司的软件平台DaVis10.0.5中加载的双脉冲双帧抖盒子算法（Shake The Box with Double Pulse-Double Frame algorithm (STB DP-DF)和新近研制的机器人型体视PIV速度矢量场测量系统，对风洞中骑自行车的假人腿部造成的阻力危机现象进行了实验研究。

采用德国LaVision公司的软件平台和四台Imager SX 4M型CCD相机。构成一套层析PIV处理系统。并利用这样的系统对受到漩涡诱导振动（VIV）影响的系留球体尾流进行了Tomo-PIV测量。

In January 2004, Memorial University purchased a stereoscopic Particle Image Velocimetry (PIV) system for making flow measurements. Although the system was potentially very versatile, its primary application was envisioned to be in a towing tank. The system was supplied as a complete package of hardware and software for calibration, data collection and analysis. The intention of the PIV system designers was to collect as many data frames as possible for a fixed measurement plane location, relative to the model. This required the PIV system to be fixed on the towing carriage, moving with the model being studied. It was found during some preliminary experiments that an active seeding delivery system was necessary to ensure sufficiently high seeding particle concentration, especially when measuring flow velocities around a model hull with a large yaw angle. This paper describes the development of a seeding technique for a PIV system that can be used in a towing tank. The paper also includes an estimate of the uncertainty of the measurement system, including the analysis of the flow behind the device used to deliver seed particles into the flow.

This paper presents an experimental study on wave interactions with a rectangular barge in a beam sea condition. Regular waves with a wave period the same as the natural frequency of the barge were used in the experiments due to the fact that the barge is prone to capsizing under such waves. The barge was fixed on the free surface and no wave overtopping was assumed. Particle Image Velocimetry (PIV) was employed to measure the full-field two-dimensional velocity. Since the flow is highly turbulent, the phase-averaging technique was used to the extract the mean flow and turbulence properties. The mean flow pattern, including velocity, vorticity, and streamline, was analyzed to quantify the mechanism of the interactions. The generation and evolution of vorticity and turbulence kinetic energy were demonstrated.The turbulent kinetic energy is found to highly correlate with the vorticity field

The vertebrate limb bud arises from lateral plate mesoderm and its overlying ectoderm. Despite progress regarding the genetic requirements for limb development, morphogenetic mechanisms that generate early outgrowth remain relatively undefined. We show by live imaging and lineage tracing in different vertebrate models that the lateral plate contributes mesoderm to the early limb bud through directional cell movement. The direction of cell motion, longitudinal cell axes and bias in cell division planes lie largely parallel to one another along the rostrocaudal (head-tail) axis in lateral plate mesoderm. Transition of these parameters from a rostrocaudal to a mediolateral (outward from the body wall) orientation accompanies early limb bud outgrowth. Furthermore, we provide evidence that Wnt5a acts as a chemoattractant in the emerging limb bud where it contributes to the establishment of cell polarity that is likely to underlie the oriented cell behaviours.

采用LaVision公司的ImagerSX4M相机，两套Infnity K2, DistaMax型长工作距离显微镜，对3.246mm x 3.874mm的视场进行了流场测量。获得了温度驱动的边界层流动的可视化流场。

Particle image velocimetry (PIV) experiments have been carried out to study the correlation between the high- Reynolds number turbulent flow and wall heat transfer characteristics in a two-pass square channel with a smooth wall and a 90
rib-roughened wall. Detailed averaged velocity distributions and turbulent kinetic energy for both the main and the secondary flows are given for a representative Reynolds number (Re) of 30,000. The PIV measurement results were compared with the heat transfer experimental data of Ekkad and Han [International Journal of Heat Mass Transfer 40 (11) (1997) 2525–2537]. The result shows that the flow impingement is the primary factor for the two-pass square channel heat transfer enhancement rather than the flow turbulence level itself. The characteristics of the secondary flow,for example,vortex’s shape, strength,rotating-direction and positions, are closely correlated with the wall heat transfer enhancements for both smooth and ribbed wall two-pass square channels. The rib-induced flow turbulence increases the heat transfer mainly because of the enhanced local flow impingement near the rib.

1.The HARVEST Project 2.2D-2C PIV Measurements 3.NumericalComputation 4.Results 1.ComparisonsPIV / CFD 2.Characterizationof dynamicstall 5.Conclusions ---------------------------------------------------------- Objective:Convertcineticenergyof riversor of tidal flow Specificity:Vertical axis turbine, radial flux, new generationof Darrieusand Gorlovturbine

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

Low-frequency combustion instabilities were studied experimentally in a model lean-premixed stepped combustor. The PLIF technique was used to characterize the flame structure. The PIV technique, associated with high-speed visualization of the OH* radical chemiluminescence’s emission, allowed to investigate the flow field during the quasi-periodic unsteady flashback when the flame lifted from the edge of the step and moved periodically in and out of the premixing duct. Results strongly suggest that impact of acoustic waves on the flame structure should be taken into account when applying LES approach to industrial gas turbines.

The prolific application of digital imaging and image processing for studying flows is extended to surface oil flow visualization. The use of colored, fluorescent mixtures enable bright, high-contrast images to be obtained which facilitate image processing. Examples were provided in visualizing the surface flow past micro vortex generators. Image processing of video sequences revealed minute features that are critical in understanding the flow.

Large scale digital particle image velocimetry (PIV) and laser speckle velocimetry (LSV) are applied to landslide generated impulse waves. The challenges posed to the measurement techniques in an extremely unsteady three phase flow consisting of granular matter, air and water are considered. Areas of interest up to 0.8 m by 0.8 m are investigated in the impulse wave generation zone. The complex flow phenomena present in the first stage of impulse wave initiation are: High speed granular slide impact, impulse flux transfer, flow separation and reattachement, cavity formation and collapse, slide deformation and penetration into fluid. During this first stage the three phases are separated along sharp interfaces changing significantly within time and space. A combined analysis method for PIV in water flow and LSV on the corona of the landslide surface is presented. Digital masking techniques are applied to distinguish between phases thereafter allowing phase separated image processing. The combination of PIV and LSV reveals insight into the impulse transfer mechanism. Applicability of PIV at large scale as well as to flows with large velocity gradients due to the presence of a strong shock are highlighted. An introductory vector-field obtained by means of PIV is shown in Fig. 1 with flow reattachement and characteristic saddle point above slide shoulder. Subsequent wave generation stages with granulate detrainment, bubble break up and massive phase mixing are not considered here.

采用LaVision的图像采集和处理软件平台以及LDY300型双脉冲PIV激光器，ImagerProSX 5M 型双帧双爆光相机，构成一套粒子成像测速系统（PIV) ，并利用该系统对轴流式血泵在三种工况下流场特性进行了实验研究

Shape memory polymer foams may be used to treat vascular aneurysms through thermal actuation of the foam from a compacted to an expanded configuration within the aneurysm structure, thereby alleviating blood pressure on the weakened aneurysm walls and reducing potential for rupture. After delivery to the aneurysm site, fiber-delivered laser light absorbed by the foam structure is converted into thermal energy, and actuation of the foam results. Introduction of nonphysiological energy into the body during foam actuation necessitates an evaluation of potential thermal damage to nearby tissue. In the present investigation, the foam is idealized as a heat-dissipating, volumetrically static object centered in a straight tube of flowing water. Velocity profiles around the heat-dissipating device are acquired experimentally with particle image velocimetry. A computational fluid dynamics package is then used to predict the experimental velocity profiles and temperature distributions by numerical solution of the Navier-Stokes and energy equations, and agreement between the computational solution and experimental results is assessed. Discussion of this assessment, as well as several preliminary procedures leading up to the creation of the heat-dissipating device and critical analysis of the methods employed, is also given. PIV and CFD are found to be in reasonable agreement with one another. Using laser-induced fluorescence as a temperature measurement modality, which is discussed in the text insofar as the technique was attempted several times and failed, together with PIV and CFD provides a formidable array of techniques exists to characterize flow around a heated device.

Thromboembolic events caused by implanted cardiovascular devices present serious challenges to surgeons and researchers alike. In particular bileaflet mechanical heart valves are prone to thrombus formation in the hinge region due to a combination of high shear stress and stagnation regions. Shear-induced platelet activation and aggregation is usually studied using viscometers, parallel plate flow, and other non-physiologic in vitro configurations. However, it is desirable to study this phenomenon in a more physiological environment.