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采用四台高速相机构成一套时间分辨层析PIV(TomoPIV)测量，外加一台红外相机测温。研究传热和速度场的关系。研究了人字形射流撞击墙壁状态下壁温与流场的相关性

采用LaVision的Imager Intense型，ImagerProX型相机。PTU9型可编程时序控制器，和软件平台，分别搭建了2DPIV,2DPTV,3D层析PIV和3DPTV测量系统，并对湍流边界层的流场进行了测量分析。

采用千赫兹重频多模激光泵浦光学参量振荡器构成的平面激光诱导荧光成像系统对燃烧火焰中的CH自由基的浓度的空间分布进行了测量。测量CH自由基所需的431nm波长处的单脉冲输出能量达到了6mJ。

1. 采用大型8.4英寸彩色液晶触摸屏，操作控制。 2. 触摸屏透过无线蓝牙操作，更加安全且降低危险性。 3. 触摸屏MCU-710连接蓄电池后，实现携带操控。 4. 用户权限设定功能，防止错误设置，管控方便。 5. 测量过程中实时显示滴定曲线、水分含量和参数。 6. 独创2.6mgH2O/min的电解速度，缩短测量时间。 7. 测量结果可存储在U盘，可生成PDF实验报告。

电极是水分测定仪的关键部件，电极表面的污染可直接导致灵敏度降低，有些电极长期应用于油质样品的分析，电极表面被油质污染后，灵敏度降低，使得电极对终点的判断迟钝，造成卡尔-费休试剂过量，终点反应时溶液颜色偏深，此时必须清洗电极。尽管肉眼看不到电极上的污染物，但可以观察到反应迟钝，直接影响测量准确性。

Plasma actuators have been identified as having great promise for flow control applications. A single dielectric barrier discharge (SDBD) plasma actuator consists of two staggered electrodes separated by a dielectric layer (Fig. 1). When an AC voltage of sufficient amplitude (a few kV) is supplied to the exposed electrode, it causes the air over the covered electrode to weakly ionize, resulting in a cold plasma. An electro-mechanical coupling with the ambient air is provided by the interaction between the ionized air and the electric field between the two electrodes, generating a body force.

Complex applications in fluid dynamics research often require more highly resolved velocity data than direct measurements or simulations provide. The advent of stereo PIV and PCMR techniques has advanced the state-of-the-art in flow velocity measurement, but 3D spatial resolution remains limited. Here a new technique is proposed for velocity data interpolation to address this problem. The new method performs with higher quality than competing solutions from the literature in terms of accurately interpolating velocities, maintaining fluid structure and domain boundaries, and preserving coherent structures.

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.

In particle image velocimetry (PIV) a temporally separated image pair of a gas or liquid seeded with small particles is recorded and analysed in order to measure fluid flows therein. We investigate a variational approach to cross-correlation, a robust and well-established method to determine displacement vectors from the image data. A “soft” Gaussian window function replaces the usual rectangular correlation frame. We propose a criterion to adapt the window size and shape that directly formulates the goal to minimise the displacement estimation error. In order to measure motion and adapt the window shapes at the same time we combine both sub-problems into a bi-level optimisation problem and solve it via continuous multiscale methods. Experiments with synthetic and real PIV data demonstrate the ability of our approach to solve the formulated problem. Moreover window adaptation yields significantly improved results.

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.

Many surfactants and polymers are considered as excellent drag reducing agents. This phenomenon induces a significant head loss reduction compared to the pure solvent. In this study an aqueous solution of CTAC/NaSal (CetylTrimethyl Ammonium Chloride and Sodium Salicylate) is used in turbulent pipe flow system. Drag reduction experiments were carried out for different experimental conditions using pressure drop measurements. At the same time the spatial velocity distribution was measured and analysed using particle image velocimetry (PIV).

Increasingly smaller electronics requires improvement in performance of cooling systems to keep it operating reliably. We present herein a novel experimental study of convective heat transfer in serpentine microchannels with segmented liquid–liquid emulsions. It is demonstrated that this concept yields significant Nusselt number enhancement in microchannel heat sinks compared to that obtained using single phase liquid cooling. Laser Induced Fluorescence (LIF) is employed to measure temperature of the coolant with and without droplets, and micro-PIV is used to determine velocity field. For the segmented flow, up to four-fold increase of the Nusselt number was observed compared to pure water flow.

Flow and far-field noise measurements are taken on a conical Convergent- Divergent nozzle similar to the nozzles employed on high-performance tactical jets. Matching flow and far-field computations are presented, produced by Large Eddy Simulation and the Kirchhoff integral method. The conditions examined are those in which the nozzle is operated at its design Mach number of 1.56 while forward flight is simulated at Mach numbers of 0.1, 0.3 and 0.8. Both measurement and LES show that increasing forward flight Mach number to the high subsonic range shortens the initial shock cell size, and weakens the shock cells induced by the nozzle throat relative to the shock cells induced by the nozzle lip. LES shows that high forward flight speed substantially reduces the noise radiated into the forward quadrant where shock noise is dominant. It also removes the screech tone entirely.

Dual particle image velocimetry (dual PIV) measurements have been performed to investigate the space–time correlations in two subsonic isothermal round jets at Mach numbers of 0.6 and 0.9. The correlation scales are analyzed along the centerline and in the shear-layer center over the first 11 jet diameters from the nozzle exit. To provide robust results over a wide range of flow conditions, these correlation scales are given in terms of their appropriate quantities, namely, the mean or rms velocity in reference to velocity and the momentum thickness or the half-velocity diameter in reference to length in the shear layer and on the jet axis, respectively. From these results, a discussion on the modeling of turbulence in jets is addressed. The self-similarity of some space correlation functions in the shear layer and on the jet axis is shown. Furthermore, far enough downstream in the shear layer, some of the ratios between the space and time scales are relatively close to the values expected in homogeneous and isotropic turbulence. It is also found that the ratio between the integral length and the time scales in the fixed frame is of the order of the local mean flow velocity. In the convected frame, the appropriate scaling factor is the rms velocity.

This article treats of the flow motion over the so-called vortex ripples which are generated by water oscillations above a sand bed. We focus mainly our experimental works on the morphology and the dynamics of transient flow patterns above real vortex ripples. With the help of flow visualizations and Particle Image Velocimetry measurements with a high-speed video CCD camera, we test numerical simulations, which predict the existence of a secondary vortex with a streamlines representation. However, our experimental findings show only one vortical structure and validate the observations of Bagnold in 1946 (using real ripples but with no visualization and measurement) and Sand Andersen & al. in 2004 (using model ripples) with respect to the existence of a transient jet.

The aim of this work was to understand the physical requirements as well as to develop methodology required to employ Time Resolved Digital Particle Image Velocimetry (TRDPIV) for measuring high speed, high magnification, near wall flow fields. Previous attempts to perform measurements such as this have been unsuccessful because of both 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 a transonic 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 a high speed high back pressure environment. Any TRDPIV measurement requires uniform spatial seeding density, but time-resolved measurements require uniform temporal seeding density as well. To this end, a high pressure particle generator was developed. This advancement enhanced current capability beyond what was previously attainable. Unfortunately, this was not sufficient to resolve the issue of seeding all together, and an advanced data reconstruction methodology was developed to reconstruct areas of the flow field that where lost do to inhomogeneous seeding. This reconstruction methodology, based on Proper Orthogonal Decomposition (POD), has been shown to produce errors in corrected velocities below tradition spatial techniques alone. The combination of both particle generator and reconstruction methodology was instrumental for successfully acquiring TRDPIV measurements in a high speed high pressure environment such as a transonic wind tunnel facility. This work also investigates the development of a turbulent wall jet.

A stereoscopic PIV system was build to study laminar turbulent transition in pipe flow. The PIV system is based on an angular displacement of the two cameras and a 3D calibration based reconstruction method. In order to measure the cross flow over the entire cross section of the pipe, the light sheet is perpendicular to the main flow direction. Measurements have shown that the PIV system is capable of detecting the laminar and turbulent flow fields over a large portion of the pipe cross section (fig.1), with increasing errors in the near wall region. In the error analysis, estimations and measurements of the registration error are shown (fig.2). The registration error is due to a small misalignment of the light sheet and the calibration plane. It is shown to make an important contribution to the total error. The transition measurements presented at the end of the paper are the result of brief test runs and are a good example of the kind of experiments planed for the near future.

We have studied the flow induced by a macroscopic spherical particle settling in a Laponite suspension that exhibits a yield stress, thixotropy, and shear thinning. We show that the fluid thixotropy
or aging induces an increase with time of both the apparent yield stress and shear-thinning properties but also a breaking of the flow fore-aft symmetry predicted in Hershel-Bulkley fluids
yield-stress, shear-thinning fluids with no thixotropy. We have also varied the stress exerted by the particles on the fluid by using particles of different densities. Although the stresses exerted by the particles are of the same order of magnitude, the velocity field presents utterly different features: whereas the flow around the lighter particle shows a confinement similar to the one observed in shear-thinning fluids, the wake of the heavier particle is characterized by an upward motion of the fluid
“negative wake”, whatever the fluid’s age. We compare the features of this negative wake to the one observed in viscoelastic shear-thinning fluids
polymeric or micelle solutions. Although the flows around the two particles strongly differ, their settling behaviors display no apparent difference which constitutes an intriguing result and evidences the complexity of the dependence of the drag factor on flow field.

Thermoacoustic refrigeration systems generate cooling power from a high-amplitude acoustic standing wave. There has recently been a growing interest in this technology because of its simple and robust 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 of some of their components such as the heat exchangers. The characterization of the flow field at the end of the stack plates is a crucial step for the understanding and optimization of heat transfer between the stack and the heat exchangers. In this study, a specific Particle Image Velocimetry measurement(PIV) is performed inside a thermoacoustic refrigerator. Acoustic velocity is measured using synchronization and phase-averaging. The measurement method is validated inside a void resonator by successfully comparing experimental data with an acoustic plane wave model. Velocity is measured inside the oscillating boundary layers, between the plates of the stack, and compared to a linear model. The flow behind the stack is characterized, and it shows the generation of symmetric pairs of counterrotating vortices at the end of the stack plates at low acoustic pressure level. As the acoustic pressure level increases, detachment of the vortices and symmetry breaking are observed.

We present in this paper a novel collaborative scheme dedicated to the measurement of velocity in fluid experimental flows through image sequences. The proposed technique combine the robustness of correlation techniques with the high density of global variational methods. It can be considered either as a reenforcement of fluid dedicated opticalflow methods towards robustness, or as an enhancement of correlation approachs towards dense information. This results in a technique that is robust under noise and outliers, while providing a dense motion field. The method was applied on synthetic images and on real experiments in turbulent flows carried out to allow a thorough comparison with a state of the art optical-flow and PIV methods.

This paper presents flow field measurements of hydrogen/methane mixtures under near blowout conditions. Previous high speed visualizations by our group of these flames shows that the blow off phenomenology varies with percentage of hydrogen [1]. This paper further characterizes the flow field of these flames using particle image velocimetry (PIV). A variety of highly dynamic flame and flow features are observed, which vary substantially with the H2 levels in the fuel. This variation is apparently due to the enhanced strain resistance of hydrogen augmented flames and flow dilatation ratio effects upon flow dynamics, particularly vortex breakdown.

In order to avoid model support interference, the flow over cylinders of varying fineness ratio (length /diameter) aligned with the free stream were examined using a magnetic suspension and balance system. The drag coefficient variation of a right circular cylinder was obtained for a wide range of fineness ratios. Particle Imaging Velocimetry (PIV) was used to examine the flow field, particularly the behavior of the leading-edge separation shear layer and its effect on the wake. Reynolds numbers based on the cylinder diameter ranged from 5x104 to 1.1x105, while the major portion of the experiment was conducted at the ReD= 1.0x105. For the moderately large fineness ratio, the shear layer reattaches with subsequent growth of the boundary layer, whereas over shorter cylinders, the shear layer remains detached. Differences in the wake recirculation region and the immediate wake patterns are clarified in terms of both the mean velocity and turbulent flow fields, including longitudinal vortical structures in the cross-flow plane of the wake. The minimum drag corresponded to the fineness ratio where the separated shear layer reattached at the trailing edge of the cylinder. The base pressure was obtained with a telemetry technique. Pressure fields and aerodynamic force fluctuations are also discussed.

Gene expression studies are important for understanding gene regulation, deducing cell signal cascades, etc. More broadly, these studies are often used to understand disease development, as specific genes are commonly up regulated in clinical pathologies. These studies can be paired with the application of a mechanical stimulus as well; for example, endothelial cells can be exposed to a defined fluid flow (physiological or pathological) in order to understand the possible mechanisms for atherosclerosis development.

Lifting surfaces are used both for propulsion and control of sea vessels and must meet performance criteria such as lift, drag, and (in some military applications)hydroacoustic noise limits. Design tools suitable to predict such criteria must handle complex flow phenomena and manage the wide range of flow scales inherent in marine applications (Reynolds numbers ~108). To date, the development of such tools has been limited by the lack of controlled experimental data in this high Reynolds numbers range. Lifting surface flow is the focus of current high Reynolds number experiments involving a two-dimensional hydrofoil in the world’s largest water tunnel, the US Navy’s William B. Morgan Large Cavitation Channel (LCC). The goal of these experiments is to provide a unique high Reynolds number experimental dataset at chord-based Reynolds numbers (Re) approaching those of full-scale propulsors (~108). This data will be used for validation of scaling laws and computational models, with particular emphasis given to the unsteady, separated, turbulent flow at the trailing edge. In addition, these experiments will provide fundamental insight into the fluid mechanics of trailing-edge noise generation in marine propulsion systems. This paper describes the experimental equipment and methods employed in the test program. Described herein is the use of the LCC’s Laser Doppler Velocimetry (LDV) capability to acquire flow velocity mean and turbulence quantities, as well as estimates of boundary layer transition. Also presented is a Particle Imaging Velocimetry (PIV) system developed for these experiments and employing seed injection upstream of the channel’s flow straightener. Finally, a description is given of instrumentation mounted in the foil for measurement of vibration and surface static and dynamic pressures.

Multiple concentrated vortices are often produced in the wake of lifting surfaces and downstream of pumps, turbines, and propulsors. The roll-up of multiple vortex strands is a common feature of these flows. In this study, we are examining the interaction of two vortices of variable strength and relative rotation (e.g. co-rotating or counter-rotating). A pair of equal-strength co-rotating vortices will merge to form a single vortex. However, as the relative strength of the vortices is decreased, the weaker vortex can wrap around the stronger vortex, causing the weaker vortex to be stretched. This stretching process can lead to cavitation inception. In the present work, we will examine this inception process.

Although turbulent jets have been studied extensively, one configuration that has not received much attention is the viscosity-stratified jet, wherein a turbulent jet of lower viscosity issues into a densitymatched host liquid of higher viscosity. We present experimental data for scalar dispersion and two-dimensional velocity measurements in the axial plane of a turbulent axisymmetric jet with a Reynolds number (Re) of 2,000 issuing into a viscous host liquid at viscosity ratios (m) ranging from 1 to 55. The presence of a strong viscosity discontinuity across the jet edge results in a significant decrease in the scalar spread rate. We attribute this to the rapid reduction in turbulence intensity and the suppression of large engulfing eddies at the jet edge. The velocity profile, on the other hand, indicates that the velocity width and mass flux reduce with increasing m up to about 20, but then increase for higher values of m. This non-monotonic variation is explained by the growing influence of viscous stress for m>20. The scalar spread rate, the velocity spread rate, the centerline velocity decay rate, and the jet mass flux are all minimized for m
20 for Re=2,000.

A survey is conducted to quantitatively visualise the wake flow behind a circular cylinder at Reynolds numbers of 180 to 2500. A time-resolved tomographic PIV method is used to measure the sequence of three-dimensional vector fields evolving in time. The attention is focused upon the unsteady 3D wake organization with the interaction of primary rollers (Karman-Benard) and the secondary vortices resulting from 3D instability of the vortex wake.

液体保温棉是一种保温材料，而保温材料一般是指热系数小于或等于0.12的材料。保温材料发展很快，在工业和建筑中采用良好的保温技术和材料可起到节约能源与改善居住环境的效果。

分析时间缩短约四倍，从而提高了常规样品分析的通量溶剂使用量与进样量降低约两倍可在HPLC仪器压力限值内(小于5000 psi)工作

在创建数字化博物馆的进程中，最主要的是对文物的数据收集，完整收集文物的颜色、形状、特征细节特征后，对数据进行修复处理，建立博物馆文物数据库。可以选择将数据进行3d打印，将原文物的复制品进行巡回展出，增加人们了解历史，了解文化。也可以选择用投影仪，3d投影仪进行展出。文物数据库建成后，后期如果文物出现损坏问题，可以根据数据库进行后期修复