其他检测

采用美国Artium公司的相位多普勒粒子干涉仪PDI对喷雾对象的体积流量进行了测量。并尝试寻找优化参数设置。结果显示，在正确设置优化测量参数的前提下，PDI测量计算体积通量的结果和作为对比的机械图样测试的结果的符合度达到了非常高的98%。

采用美国Artium公司的PDI-200MD型相位多普勒粒子干涉仪（PDI）对多横流角喷流羽流的液滴的粒径和速度进行了测量，并和CFD计算结果进行了对比分析。

采用立陶宛Ekspla公司的Ekspla NL640 型二倍频SHG调QNd: YAG激光器。脉冲宽度10ns。波长532 nm. 重复频率200 Hz。聚焦光腰直径20μm.焦点处光功率密度可达113MW/cm^2。采用Z扫描技术对掺镧TiO2纳米阵列的线性和非线性光学响应特性进行了实验研究。

采用10赫兹200毫焦单脉冲能量的Nd:YAG激光器做光源，用两台SensiCam PCO相机做成像部件，加上LaVision公司的DaVis7.2和8.0软件平台，构成了一套立体3维粒子成像测速系统(PIV)。用此系统，对马赫数2.75的超音速激波风洞中的三维激波/边界层相互作用的间歇分离和涡结构关系进行了研究。得到了许多重要结果。

采用美国Artium公司的无需光纤的半导体泵浦的固体激光器（DPSSL）集成在发射头内的激光相位多普勒粒子干涉仪，对高雷诺数湍流中的惯性粒子团聚线性进行了实验研究和分析。

A new method to describe small scale statistical information from passive scalar fields has been proposed by Wang and Peters (2006). They used direct numerical simulations (DNS) of homogeneous shear flow to introduce the innovative concept. This novel method determines the local minimum and maximum points of a fluctuating scalar field via gradient trajectories starting from every grid point in the direction of the steepest ascending and descending scalar gradients. Relying on gradient trajectories, a dissipation element is defined as the region of all the grid points the trajectories of which share the same pair of maximum and minimum points. The procedure has also been successfully applied to various DNS fields of homogeneous shear turbulence using the three velocity components and the kinetic energy as scalar fields. To validate statistical properties of these elements derived from DNS (Wang and Peters 2006, 2008), dissipation elements are for the first time determined based on experimental data of a fully developed turbulent channel flow. The dissipation elements are deduced from the gradients of the instantaneous fluctuation of the three velocity components u5, v5, and w5 and the instantaneous kinetic energy k5, respectively. The required 3D velocity data is obtained investigating a 17.82 × 17.82 × 2.7 mm3 (0.356
× 0.356
× 0.054
) test volume using tomographic particle-image velocimetry (Tomo-PIV). The measurements are conducted at a Reynolds number of 1.7× 104 based on the channel half-height
and the bulk velocity U. Detection and analysis of dissipation elements from the experimental velocity data are presented. The statistical results are compared to the DNS data from Wang and Peters (2006, 2008).

The influence of the pulse duration was investigated using a picosecond pulsed laser (Atlantic 532, Ekspla) with a wavelength of 1064 nm, a pulse duration of 10 ps, a pulse energy of 160 μJ, a repetition rate of 100 kHz, and a focal distance of 100 mm.

非介入式全场应变形变测量，可用于各种材料压缩和拉伸形变试验中，也可用于冶金，地质，矿产研究和工业领域。

该文报道了瑞典Chalmers University of Technology大学燃烧发动机研究中心内(Combustion Engine Research Center – CERC)在发动机燃烧,喷雾等方面研究成果,对喷雾D32全局当量粒径分布测量,喷雾气液两相转换等研究具有重要的参考价值.

The unsteady pressure field is obtained from time-resolved tomographic particle image velocimetry (Tomo-PIV) measurement within a fully developed turbulent boundary layer at free stream velocity of U∞ = 9.3 m/s and Reθ = 2400. The pressure field is evaluated from the velocity fields measured by Tomo-PIV at 10 kHz invoking the momentum equation for unsteady incompressible flows. The spatial integration of the pressure gradient is conducted by solving the Poisson pressure equation with fixed boundary conditions at the outer edge of the boundary layer. The PIV-based evaluation of the pressure field is validated against simultaneous surface pressure measurement using calibrated condenser microphones mounted behind a pinhole orifice. The comparison shows agreement between the two pressure signals obtained from the Tomo-PIV and the microphones with a cross-correlation coefficient of 0.6 while their power spectral densities (PSD) overlap up to 3 kHz. The use of the Tomo-PIV system with the application of three-dimensional momentum equation shows higher accuracy compared to the planar version of the technique. The combination of a correlation-sliding-average technique, the Lagrangian approach to the evaluation of the material derivative and the planar integration of the Poisson pressure equation results in the best agreement with the pressure measurement of the surface microphones.

• 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-dimensional velocity fields. • PIV has facilitated detailed measurements of a wide variety of phenomena in complex (dusty) plasmas from particle transport to DAW/DDW to thermal properties. • New developments: o Detailed benchmarking of PIV against simulations o Spatially resolved stereo-PIV o Tomographic PIV o Time-resolved PIV

The purpose of this experimental study was to analyze a 2D cavitating shear layer. The global aim of this work was a better understanding and modeling of cavitation phenomena from a 2D turbulent shear flow to rocket engine turbopomp inducers. This 2D mixing layer flow provided us a well documented test case to be used for comparison between the behavior with and without cavitation. Similarities and differences led to characterize effects of the cavitation on the flow dynamic.

The shear layer instability in the flow between two counter-rotating disks enclosed by a cylinder is investigated experimentally and numerically, for radius-to-height ratio Γ =R/h between 2 and 21. For sufficiently large rotation ratio, the internal shear layer that separates two regions of opposite azimuthal velocities is prone to an azimuthal symmetry breaking, which is investigated experimentally by means of visualization and particle image velocimetry. The associated pattern is a combination of a sharpcornered polygonal pattern, as observed by Lopez et al. (2002) for low aspect ratio, surrounded by a set of spiral arms, first described by Gauthier et al. (2002) for high aspect ratio. The spiral arms result from the interaction of the shear layer instability with the Ekman boundary layer over the faster rotating disk. Stability curves and critical modes are experimentally measured for the whole range of aspect ratios, and are found to compare well with numerical simulations of the three-dimensional timedependent Navier–Stokes equations over an extensive range of parameters. Measurements of a local Reynolds number based on the shear layer thickness confirm that a shear layer instability, with only weak curvature effect, is responsible for the observed patterns. This scenario is supported by the observed onset modes, which scale as the shear layer radius, and by the measured phase velocities.

The performance of a vertical axis wind turbine with and without a diffuser was studied using direct force measurement technique applied to a scaled model of the rotor in a water tunnel. The experiment was conducted at different tip-speed ratios. The maximum power coefficient for the turbine was found to be equal to 0.35 for the rotor with diffuser and to 0.26 for the rotor without diffuser. Therefore, the maximum power coefficient was increased by 35% when the diffuser was used in the configuration. In the second part of this work, the flow patterns downstream of the turbine were studied by the particle image velocimetry (PIV) technique. Six different tip-speed ratios were considered for each configuration (with and without a diffuser). The vorticity and the streamline plots provide insight into the flow physics in each configuration. In addition, the swept area of a full-scale rotor was calculated for both a diffuser-augmented and a bare turbine for a range of power outputs.

The purpose of this experimental study was to analyze a two-dimensional cavitating shear layer. The global aim of this work was to improve understanding and modeling of cavitation phenomena, from a 2D turbulent shear flow to rocket engine turbopomp inducers. This 2D mixing layer flow provided us with a well documented test case to be used for comparisons between behavior with and without cavitation. Similarities and differences enabled us to characterize the effects of cavitation on flow dynamics. The experimental facility enabled us to set up a mixing layer configuration with different cavitation levels. The development of a velocity gradient was observed inside a liquid water flow using PIV–LIF (particle image velocimetry–laser induced fluorescence). Kelvin-Helmholtz instabilities developed at the interface and vaporizations and implosions of cavitating structures inside the vortices were observed. The mixing area grew linearly, showing a constant growth rate, for the range of cavitation levels studied. The spatial development of the mixing area seemed hardly to be affected by cavitation. Particularly, the self-similar behavior of the mean flow was preserved despite the presence of the vapor phase. Successive vaporizations and condensations of the fluid particles inside the turbulent area generated additional velocity fluctuations due to the strong density changes. Moreover, when cavitation developed, the Kelvin-Helmholtz vortex shape was modified, inducing a strong anisotropy (vortex distortion as ellipsoidal form) due to the vapor phase. The main results of this study clearly showed that the turbulence-cavitation relationship inside a mixing layer was not simply a change of compressibility properties of the fluid in the turbulent field, but a mutual interaction between large and small scales of the flow due to the presence of a two-phase flow.

Proper Orthogonal Decomposition (P.O.D.) is a technique used for analysis of vortex structures in a turbulent flow. In this study, complex shear flows are observed by P.I.V. measurements (Particle Image Velocimetry) of a large diameter ratio annular jet. The annular jet is an example of complex shear flow situations. Two axisymmetric shear layers, originating at the jet exit, one at the nozzle lip and the other at the centre body, eventually meet downstream or interact with each other. The main aim of this study is to observe and analyze the effects of active control using acoustic waves on an annular jet with a great diameter ratio (r= 0.91), in order to find a new way to reduce jet instabilities. This contribution discusses the application of Proper Orthogonal Decomposition to the P.I.V. (Particle Image Velocimetry) velocity fields of an annular jet and on a statistic of time resolved tomographic images of the initial zone of the annular jet. Acoustic waves are then applied on the annular jet with different frequencies (fundamental, first harmonic̷). Measurements are conducted with a Reynolds number ReDo=107800. The fluctuation frequency of the stagnation point is known for this Reynolds number. The Strouhal number corresponding to this frequency is StDo = 0.27. The P.O.D. analysis applied on a natural annular jet and an excited annular jet enables us to see the importance of the triggering of the acoustic wave with the stagnation point motion. An active control is therefore necessary to use acoustic excitation to reduce instabilities in the initial zone of these turbulent jets. Active control has already been used with round jets and has given promising results, but only a few studies have been conducted on annular jets in this field. This work will permit us essentially to have a better knowledge of annular jets and to meet manufacturers' needs.

A complementary experimental and computational study of plunging breaking waves is presented that are generated in a two dimensional open channel flume using a bottom bump and impulsive accelerated flow. The time evolution of the transient wave and its flow properties are measured using experimental fluid dynamics (EFD): upstream and downstream velocity and flow rates using pitot probes; air-water interface elevation measurements and two dimensional particle image velocimetry in the wave breaking region. The computational fluid dynamics (CFD) methods are: Cartesian grid; embedded- boundary; hybrid HSM/GF/particle level set and VOF methods, and LES. CFD wave profiles at various time steps identifies the overall wave breaking process and major events: max wave height, first plunge, oblique splash-up, vertical jet, air entrainment, two repeats of these processes, dissipation and wave swept downstream which is qualitatively validated by EFD results. Both EFD and CFD results showed two subsequent plunging and splash-up events after the first plunge. After the wave breaks, the flow trends in mean velocity and vorticity observed in EFD are very similar to CFD which has more detailed resolutions of plunging, splashing, vertical jet and bubble entrainment. Current studies also revealed the occurrence of chaotic multiple splash-up events after the third plunging that produce span-wise vorticity and turbulence. Generation of a clockwise rotating bump vortex and an anticlockwise rotating span-wise wave breaking vortex that is created from the entrapped air after the breaking which transports turbulence from the trough towards the bulk fluid, were identified as the two important events. Mean values of turbulent kinetic energy (TKE) below the broken wave showed that the TKE levels increase by almost 90% after the first plunge and another 40% after the second plunge, after which as the wave is swept downstream by the accelerating mean flow the TKE dissipates.

This research investigated multiple detonation diffraction events in order to better understand the limits and benefits of diffraction strategies with respect to pulse detonation engine design. Hydrogen/air detonations were generated using swept ramp obstacles in a 1.27 m long channel with a cross section of 25.4 mm by 88.9 mm and were diffracted into various multiple-stepped openings. This allowed the detonation wave diffraction transmission limits to be determined for hydrogen/air mixtures and to better understand reinitiating mechanisms throughout the diffraction process. Tests were conducted for area ratios ranging from 2.00–2.60 with varying equivalence ratios from 0.5–1.5. Computational methods were used to better understand the diffraction phenomenon using a series of sensitivity studies for different chemistry sets, computational cell size and equivalence ratio. Experimental tests used combined optical shadowgraph and particle image velocimetry imaging systems to provide shock wave detail and velocity information. The images were observed through a newly designed explosive proof optical section and split flow detonation channel. It was found that area ratios of 2.0 could survive single and double diffraction events over a range an equivalence ratio range of 0.8 to 1.14 Area ratios of 2.3 survived the primary diffraction event for equivalence ratios near stoichiometric for the given step length. Detonation diffraction for area ratios of 2.6 did not survive the primary diffraction event for any equivalence ratio and were unable to transmit to a larger combustor.

To quench a thermal runaway reaction in a chemical rector, an efficient approach is the introduction of a small quantity of a liquid inhibiting agent, named a “killer”, into the mixing vessel. In this thesis, an experimental approach has been coupled tightly with numerical modelling using Computational Fluid Dynamics (CFD). The first part of this thesis is devoted to a study of the hydrodynamics of partially-baffled mixing vessels, including the free-surface deformation caused by the central vortex. The use of an inhomogeneous, multiphase approach allowed simulation of the free-surface deformation. The capability of this novel method was demonstrated by very good agreement between the numerical predictions and experimental data. In the second part, liquid jet injection at the free-surface was coupled with the vessel hydrodynamics. Numerical results, obtained using an Eulerian-Lagrangian approach, have again shown good agreement with experimental data. These results allowed the jet trajectory to be modelled and its penetration into the agitated vessel was quantified. New mixing criteria were introduced that are specific to this application. Finally, the numerical methods validated at the pilot scale were applied at the industrial scale and allowed the proposal of practical improvements to the safety of the synthesis reactors studied.

Acceleration is of primal relevance in fluid mechanics, as it shows the effect of the combination of all the forces acting on a fluid flow; the Navier-Stokes equations highlight this fact and the importance of its knowledge in the description of a fluid motion: Moreover, only in few particular cases (as for example, in parallel fluxes such as Couette one) it is possible to analytically solve them: for the other cases it would be important to measure their single components. Unfortunately, despite the acceleration is at the very base of fluid motion (see, for instance, Tsinober 2001), only few measurement of the acceleration in the Lagrangian frame can be found in literature. Even if, on one hand, a certain number of authors have studied acceleration properties via numerical simulations, for instance Vedula and Yeung (1999), Tsinober et al. (2001), Biferale et al. (2004), Goto et al. (2005), Osborne et al. (2005), Chen et al. (2006), on the other very few examples of its experimental measure are available up to now. Moreover,among them not all the measurements are taken in the Lagrangian frame: among the Eulerian measurements, Christensen and Adrian (2002), Dong et al. (2001) and Lowe and Simpson (2005) can be pointed out, among the Lagrangian ones, Virant and Dracos (1997), Ott and Mann (2000), La Porta et al. (2001), Voth et al. (2002) and Luthi et al.(2005) can be found.

Active flow control earns growing interest for manufacturers of large transport aircraft because of the constant need to improve these aircraft in terms of less fuel consumption, higher efficiency, steep approaches and departures and less weight. Flow control devices that are based on fluidic actuators, e.g. vortex generator jets (VGJs), have shown a promising potential to influence separating boundary layers and keep them attached (e.g. Godard & Stanislas (2006a‐c); Johari. & Rixon (2003); Johnston & Nishi (1990); Mc Manus et al. (1996); Ortmanns et al. (2008a); Pauley & Eaton (1988); Scholz et al. (2006)). For an efficient operation such devices need to be optimized regarding their ability to influence the flow. However, optimization turns out to be very challenging because of the vast parameter space and the lack of an adequate “figure of merit”. The proposed contribution will discuss the possibility to assess and optimize such devices by analyzing the velocity fields from stereoscopic PIV measurements.

Electron heating, mechanisms of plasma generation, and electron dynamics in dif- ferent types of capacitively coupled radio frequency (CCRF) discharges relevant for industrial applications are investigated by a combination of di®erent experimen- tal diagnostics, simulations and models. Geometrically symmetric and asymmetric single frequency discharges operated at low pressures, geometrically symmetric dual frequency discharges operated at two substantially di®erent frequencies and two sim- ilar frequencies (fundamental and second harmonic with variable phase shift between the driving voltages) as well as hybrid capacitively/inductively coupled (CCP-ICP) RF discharges are studied. Electron heating is found to be strongly a®ected by phenomena characteristic for a certain discharge type, that do not occur in another. At low pressures the generation of highly energetic electron beams by the expand- ing sheath is observed. Such beams propagate through the entire plasma bulk and are re°ected at the opposing plasma boundaries, if the electron mean free path is long enough. An analytical model demonstrates that these beams lead to an en- hanced high energy tail of the electron energy distribution function and are, there- fore, closely related to stochastic heating

In the Fluid project, WorkPackage 1 is devoted to the creation of an image sequence database with controlled 2D/3D experimental and numerical ow elds. The objective of this workpackage is to produce complete sets of data comprising:  meteorological satellite atmospheric image sequences;  rst sets of image sequences of controlled uid mechanics experiments (air ows in wind tunnels), produced in a classical way using laser-sheets and cameras, with a smoke or particle concentration chosen a priori in order to give reasonably detectable contrasts;  second sets of experimental image sequences produced in an adapted manner (seeding, lighting, frame size, physical data range) after feedback from tests conducted in WP 2, WP 3 and WP 4;  synthetic image sequences coming from the results of Direct Numerical Simulations (DNS) of shear ows;  quantitative data characterising the ows corresponding to each set of experimental image sequences, among which global and local physical characteristics like velocity elds, statistics, spatial correlation as well as topological dimensions of specic regions of the ow (formation length, layer thickness, virtual origins, wave length, etc). This report is the deliverable D1.23 on the production and diusion of uid mechanics images and data. All the dataset distributed during the rst year to the dierent partners are described. Section 2 concerns two experimental datasets, the rst one is not time resolved but the second is. Section 3 presents 2D-synthetic data of analytic ows, DNS of 2D sustained turbulent ow and a sample of 2D ow from PIV Challenge. The last section 4 is devoted to 3D-synthetic data.

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).

Vertical slot fish passes have been applied as a solution to mitigate fish migration problems in running waters, for over two decades. They are commonly used to enable target fish to ascend through obstacles in rivers. However, small species are rarely considered in such fishways, of which the performance for small fish still remains unknown. This experiment was to study the turbulence structure in a vertical slot fish pass concerning two different pool length/width ratios of 9 and 6.67 as well as the effect of installing a cylinder behind the slot in affecting the characteristics of instationary flow. Cylinders are considered an effective solution to modify the flow structure and to reduce velocity and turbulent energy in order to adapt the flow for the passage of small fish species. Flow visualization and particle image velocimetry were used to study the characteristics of mean flow and turbulence and particular emphasis on the unsteady flow. The results show that flow patterns consist of a water jet and one or two recirculation zones depending on the length/width ratio of the pool. The direction of the jet was strongly affected by the vertical cylinders. The frequencies and spatio-temporal evolutions of the main jet beats were analyzed. Combining with the previous studies of fish migration experiments, the results provide hydraulic evidence on the biological performance.

In this paper we experimentally study the effect of collision properties of different particle systems on the bed dynamics of a spout fluidized bed. This is done for different flow regimes: the spout-fluidization regime (case A), the jet-in-fluidized-bed regime (case B) and the spouting-with-aeration regime (case C). The considered particle systems comprise glass beads, -alumina oxide and zeolite 4A particles, which are all classified as Geldart D. A nonintrusive measurement technique is used, viz. particle image velocimetry (PIV) to measure the particle flow field in a pseudo two-dimensional (2D) spout fluidized bed. Additionally, digital images are analyzed using a newly developed digital image analysis (DIA) algorithm to evaluate the particle volume fraction. It is demonstrated that the new proposed DIA algorithm provides reliable information on the particle volume fraction distribution, showing that it is a powerful tool when combined with PIV. The added value of DIA is confirmed by comparing the particle velocity fields and volumetric particle fluxes. The effect of the collision properties for glass beads, - alumina oxide and zeolite 4A particles has been studied in three flow regimes, i.e. the intermediate/spout-fluidization regime (case A), the jet-in-fluidizedbed regime (case B) and the spouting-with-aeration regime (case C). For each flow regime, the particle volume fraction shows small differences between the different particle systems. For the -alumina oxide and zeolite 4A particles, the spout channel is less stable for the cases A and C. The particle fluxes display also small differences between the particle systems for each flow regime.

In this paper, we study the acoustic emissions of the flow over a rectangular cavity. Especially, we investigate the possibility of estimating the acoustic emission by analysis of PIV data. Such a possibility is appealing, since it would allow to directly relate the flow behavior to the aerodynamic noise production. This will help considerably in understanding the noise production mechanisms and to investigate the possible ways of reducing it. In this study, we consider an open cavity with an aspect ratio between its length and depth of 2 at a Reynolds number of 2.4 9 104 and 3.0 9 104 based on the cavity length. The study is carried out combining high speed two-dimensional PIV, wall pressure measurements and sound measurements. The pressure field is computed from the PIV data. Curle’s analogy is applied to obtain the acoustic pressure field. The pressure measurements on the wall of the cavity and the sound measurements are then used to validate the results obtained from PIV and check the range of validity of this approach. This study demonstrated that the technique is able to quantify the acoustic emissions from the cavity and is promising especially for capturing the tonal components on the sound emission.

In current wing design, multiple flaps are incorporated into the trailing edge to allow mixing of high and low pressure sides to reduce flow separation. These flaps reduce the efficiency by adding weight and complexity to the aircraft. A single hinged flap would reduce these inefficiencies but is more susceptible to flow separation. Active flow control is a means by which the fluid flow over a body is deliberately altered and can be altered such that it becomes less likely to separate from the object. By energizing the flow, the degree of separation of the flow can be controlled, and this inherently controls lift. Dielectric barrier discharge (DBD) plasma actuators are a form of active flow control. These actuators are created by asymmetrically aligning two electrodes and adding a dielectric layer between the electrodes. When the electrodes are electrically connected, ionized air (plasma) travels from the exposed electrode towards the covered electrode. Collisions occur between the plasma and neutral air over the body, and momentum is transferred to the neutral air, effectively energizing it. The purpose of this study is to examine the lift enhancement and flow control authority that multiple DBD plasma actuators have on a high-lift airfoil when compared to the flow exhibited by noncontrolled and single DBD plasma actuator controlled cases. Electrodes were mounted onto a simplified NASA Energy Efficient Transport airfoil near the flap. The airfoil was tested in a closed, recirculating wind tunnel operating at a Reynolds number of 240,000, 20° flap deflection angle and 0° degree angle of incidence. The actuators were independently powered in order to determine the most effective input parameters. Using multiple actuators operated in-phase has increased the lift and has delayed flow separation on the trailing edge flap when compared to baseline and single actuation cases.

相位多普勒干涉测量术探测区域和粒子粒径比值小于一（第二部分 该技术的应用）。采用最新型的DPSSL激光器取代传统的氩离子激光器，具有光束相干性好，干涉条纹对比度强，测量精度和数据有效率高，调试简单快捷的突出优点。

Invention of the 3D detector approach for extending the measurement range and signal validation, W.D. Bachalo 1982.