湍动边界层

采用LaVision的图像增强器IRO和DaVis8.3软件平台，搭建一套利用甲苯作为测温标的物的示踪PLIF-测量系统。并利用该系统对热边界层的温度场分布进行了实验测量和分析。

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LaVision的时间分辨体视层析粒子成像测速系统(TRTOMO-PIV)对低速湍流边界层中流场的相干结构进行了详细讨论和研究。

采用两组每组8台相机(LaVision Imager ProHS) 构成一套组合的3D3C体视抖盒子测量系统。每组相机系统可以获得90 × 60 × 25 cm3大小的体视流场，两套系统测量对象空间有30cm重叠，最终实现150 × 60 × 25 cm3尺度的流场测量结果。并将之应用于湍流边界层。

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。

采用一台Quantronix公司生产的Darwin Duo型双腔Nd:YLF激光器作光源。该激光器输出2 × 25 mJ 单脉冲能量，重复频率1 kHz。采用两台Photron Fastcam SA1 相机作成像器件。构成一套时间分辨高重复频率立体3维粒子成像测量系统。对NACA 0018翼型，加装整齐排列的锯齿状后缘时的流动的边界层特性和声学特性进行了测量。和未加装翼型的特性做比较，得到加装锯齿状后缘，可降低气动噪声的结论。

The unsteady pressure field is obtained from time-resolved tomographic particle imagevelocimetry (Tomo-PIV) measurement within a fully developed turbulent boundary layer at free streamvelocity of U∞ = 9.3 m/s and Reθ = 2400. The pressure field is evaluated from the velocity fieldsmeasured 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 withfixed boundary conditions at the outer edge of the boundary layer. The PIV-based evaluation of thepressure field is validated against simultaneous surface pressure measurement using calibrated condensermicrophones mounted behind a pinhole orifice. The comparison shows agreement between the twopressure signals obtained from the Tomo-PIV and the microphones with a cross-correlation coefficient of 0.6while their power spectral densities (PSD) overlap up to 3 kHz. The use of the Tomo-PIV system with theapplication of three-dimensional momentum equation shows higher accuracy compared to the planar versionof the technique. The combination of a correlation-sliding-average technique, the Lagrangian approach tothe evaluation of the material derivative and the planar integration of the Poisson pressure equation results inthe best agreement with the pressure measurement of the surface microphones.

A flat plate boundary layer flow was generated at the open test section of the circuit type 1m- wind tunnel ofthe DLR, Gottingen, at a free stream velocity of U亣 = 7 m/s with zero pressure gradients. A transparent andsmooth surface glass plate is utilized to provide optical access from its bottom and a good flow quality. Theplate has an elliptic leading edge to prevent flow separation. Four tripping wires, one with 1.5 mm diameterand three with 1 mm diameter were positioned with 1 mm x-distance close to the surface at (Rex). . 290along the whole span-wise elongation of the plate. This bypass transition of the flow results in thedevelopment of a turbulent boundary layer flow. In a box of about 34 x 18 x 35 mm3 in x-y and z-directionsaround (Rex). . 450 tracer particles has been illuminated by laser light pulses at 4 kHz with 21 mJ each inorder to achieve PIV recordings without using the frame straddling method. The light source was a Nd:YAGlaser from Lee Laser inc. Two highly reflective dielectric mirrors aligned in the x-y-direction are installednearly parallel and close to the surface of the flat plate on opposite sides of the measurement region. Thecollimated laser beam undergoes multiple reflections between the two mirrors passing through themeasurement volume approximately 15 times before exiting (see sketch left). This arrangement resulted ina light amplification with a factor ~5 with respect to a single pass system. The specific illuminationarrangement has the advantage that all viewing directions collect scattered light both in forward andbackward directions, which provided the level of light needed for imaging particles in the whole volume.

The spatial and temporal development of turbulent boundary layer flows is governed by the self-organizationof coherent structures like hairpin-like or arch vortices and spanwise alternating wall bounded low- and highspeedstreaks. For a detailed analysis of the topologies of the wall normal fluid exchange namely of the fourquadrants of the instantaneous Reynolds stresses Q1,…,Q4 a 4D- measurement technique is desired.In this feasibility study the tomographic PIV technique (Elsinga et al. 2005) has been applied to time resolvedPIV recordings. Four high speed CMOS cameras are imaging tracer particles which were illuminated in avolume inside a boundary layer flow at 4 kHz by using two high repetitive Nd:YAG pulse lasers. Theinstantaneously acquired single particle images of these cameras have been used for a three dimensionaltomographic reconstruction of the light intensity distribution of the particle images in a volume of voxels(volume elements) virtually representing the measurement volume. Each of two subsequently acquired andreconstructed particle image distributions are cross-correlated in small interrogation volumes using iterativemulti-grid schemes with volume-deformation in order to determine a time series of instantaneous 3D-3Cvelocity vector fields.

The unsteady organization and temporal dynamics of the interaction between a planarshock wave impinging on a turbulent boundary layer at a free stream Mach number ofM∞ =1.69 is investigated experimentally by means of dual-plane Particle Image Velocimetry(dual-PIV). Two independent PIV systems were combined in two component mode to obtaininstantaneous velocity fields separated by a prescribed small time delay. This enables toobtain, in addition to mean and statistical flow properties, also instantaneously time resolveddata to characterize the temporal dynamics of the flow phenomenon in terms of time scales,temporal correlations and convective velocities. The characteristic time scales for theincoming boundary layer, the separation region and the reflected shock are evaluated bymeans of measuring the temporal auto-correlation coefficient in the complete flow field for arange of time delays from 5 ms to 2000 ms. These auto-correlation fields are used to quantifythe time scales in selected regions of the flow. This permits resolving the dominant timescales within the boundary layer and the interaction region.I. Introduction

One of the fascinating phenomena of natural science which has gripped the attention ofmany scientists is the problem of turbulence. Besides the ubiquitous variety and beautyof turbulent phenomena, the inherent fascination and attraction are strongly connectedwith the enormous difficulties associated to its physical and mathematical understanding.As a general solution is out of reach, the properties of different idealized flows with simplegeometries are being examined experimentally and numerically.Since its discovery by Prandtl, the boundary layer has been a subject of growing interestand is still an active subject of research. Due to both its fundamental and technicalinterest, the fully developed turbulent boundary layer in a nominally zero pressure gradient(ZPG) has been examined extensively. A flow of equal importance and perhaps morewidely observed in practice is the turbulent boundary layer (TBL) in the presence of anadverse pressure gradient (APG). This flow has not received the same attention as theZPG TBL due to its increased complexity and the necessity of firstly understanding theZPG situation.

LaVision公司的3D3C层析粒子成像测试系统(Tomo-PIV)可以获得瞬时三维体空间流动的全场三分量速度矢量场。利用这一结果数据，通过vortex-in-cell (VIC)方法，可以求出流体压力场。

采用LaVision的数字图像相关软件包DIC，对沙箱模型中沙层的运动，形变进行了测量分析，模拟了半地堑俯冲过程，获得了深入的信息信息。该实验结果，有助于对日本海沟浅层边界断层厚变形带动态形成过程的了解。

利用LaVisin公司提供的高速CMOS相机和高速图像增强器HS-IRO构成一套时间分辨PIV和PLIF联合测试系统，用于分析双稳态湍动旋流火焰中进动涡核（PVC）形成和火焰形状变化之间瞬态耦合过程。

激光器采用Quantronix 双腔高重复率激光器。单脉冲能量25 mJ @ 1 kHz。系统配备6台Photron CMOS 相机。满帧分辨率1024 x 1024像素。

Much progress has been made in the understanding of the phenomenon of drag reduction by dilute solutions of polymers since its discovery in 1948. While the use of advanced techniques in experiments and computational simulations have dramatically advancedour understanding of the phenomenon, a complete and conclusive explanation of the physics associated with the phenomenon is still lacking. In particular, drag reduction in boundary layers with injection has not been studied extensively to understand the processes and physics that govern the spread and mixing of the injected polymer in the flow. To overcome this limitation, in the present work, drag reduction due to polymer injection in a turbulent boundary layer is studied using simultaneous Particle ImagingVelocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF). PIV is used to measure the velocity of the flow in the boundary layer and to calculate higher order velocity statistics. PLIFis used to study the distribution and spread of the injected polymer in the boundary layer by tracking a fluorescent dye mixed in with it. The polymer of choice, polyethylene oxide, is injected as a dilute solution into a fully turbulent Newtonian boundary layer and measurements of velocity and concentration are made at different downstream locations on the flat plate to study the effect of the polymer on the flow and the evolution of drag reduction. The data from the two measurement techniques are combined to calculate turbulent fluxes and to estimate the turbulent Schmidt number in polymer drag reduced flows.

采用ImagerProX4M相机。长工作距离显微镜。测量一个粗糙的砂轮圆盘在液体池中旋转时所产生的流场。

This student research project deals with the investigations of the flow phenomena over athree dimensional moving airfoil. The complex motion apparatus was set up to create apitching, plunging and rolling movement of a two dimensional wind tunnel model. The mainobjective was to determine the position of transition with respect to the phase angle andspan-wise distribution. The campaign focussed Stereo PIV measurements, but also MiniTuft-, Oilfilm- and SSLCC- Techniques, contributed to the results. It can be shown that theflow field is not dominated by side-wall effects, while the transition oscillates correspondingto the spanwise variation of the heaving cycle.

采用德国LaVision公司2D2C平面粒子成像测速(PIV)系统。对边生物工程涂料边界层流场，采用高空间分辨率的PIV+PTV分析方法计算流体速度矢量场，分析了生物工程涂料用于被动流动控制的可行性。

采用表面印刷工艺的软塑包装的油墨层在包装袋表面的附着牢度是关系到印刷字迹、图案是否易发生脱落的重要因素。本文通过对某速冻产品包装薄膜表面墨层结合牢度的检测，介绍了一种验证包装印刷质量的试验方法，并对试验过程、Labthink兰光BLJ-02圆盘剥离试验机和YGJ-02胶粘带压辊机等试验设备进行了简单的描述，为企业检验包材的印刷效果提供参考。

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。

In the present study it is attempted to use the 3D time-resolved velocity field measurementsobtained by employing a high-speed tomographic PIV system on a flat plate turbulent boundary layer atReθ=730. The main objective of the study is the estimation of the wall pressure coherence function for theprediction of aeroacoustic noise radiated by boundary layers and trailing edge flows. The reconstruction ofthe pressure field from velocity field measurements follows the approach of de Kat and van Oudheusden(2012), whereby the Poisson equation is integrated over the measurement volume in 3D. Due to restrictionon the extent of the measurement volume, uniform pressure is applied as boundary condition on stream- andspanwise faces.A direct numerical simulation of the boundary layer at a similar Reynolds number is performed in order toproduce reference data for the velocity statistics and for the properties of the spectral fluctuations. Thetomographic data agree very well with DNS as far as mean and fluctuating velocity components areconcerned.Velocity field results are compared to 2C-PIV and the DNS solution and a collapse of the data isdemonstrated. An additional reference measurement is introduced in order to validate the procedure ofpressure determination from time-resolved tomographic PIV. Time series of pressure and the scaled powerspectral density at a single point are compared to the DNS solution and results available from literature andgood agreement is found. The correlation coefficient with respect to pinhole microphone measurementsreaches a maximum value above 50% for data band-pass filtered between 250Hz and 3.5kHz. Finally, thecoherence of the pressure fluctuations and the resulting spanwise coherence length are computed compared.

Particle image velocimetry (PIV) is utilized with solid carbon dioxide (CO2)seeding material to conduct boundary layer measurements in the test section of the AirForce Research Laboratory’s Trisonic Gas-dynamics Facility (TGF), which has a 24 inchby 24 inch cross-section. Freestream velocity was set at Mach 0.3, Mach 0.5, or Mach0.8 while stagnation pressure ranged from 500 to 2400 pounds per square foot (psf). Highpressure liquid CO2 was directed through expansion nozzles into shroud tubes which ledto solidified particles in the wind tunnel stagnation chamber. Two different sets ofshroud tubes were used to modify the size of dry ice particles produced and the particlenumber density. Shroud tubes with an inside diameter (ID) of 0.824 inches providedgood particle count and coverage for stagnation pressures between 500 and 1500 psf,while 0.364 inch ID shroud tubes demonstrated good particle count and coverage forstagnation pressures over 1000 psf. Overall, the PIV results produced freestream velocitymeasurements and boundary layer profiles which compared well with expected values.After initial processing, turbulence data closely followed trends expected withinboundary layer, but levels were somewhat higher than anticipated. When the PIV datawas processed using elliptical interrogation regions, elongated in the streamwisedirection, resulting turbulence levels were much closer to expectations.

摘要: 借助质构分析仪, 采用单项和正交的方法, 研究了4 种面团改良剂对焙烤用冷冻面团抗拉伸特性的影响, 结果表明: 单甘酯( DMG) 0.3 %、硬脂酰乳酸钠( SSL) 0.3 %、硬脂酰乳酸钙( CSL) 0.3 %、瓜尔豆胶0.8 % 单项添加时, 以及按照DMG:SSL:CSL:瓜尔豆胶=4:3:2:12 比例复合添加, 冷冻面团的抗拉伸性良好。并以此配合进行了冷冻面团制品的焙烤对照试验, 添加改良剂的制品的比体积、表皮颜色、形状、瓤芯质地结构、色泽、平滑度、芯弹柔性和口感都好于对照制品。

1, a=radius). The experiments use conventional test methods in conjunction with Stereo Particle Image Velocimetry (SPIV) measurement techniques to evaluate the flow in the boundary region of a small diameter flexible cylinder towed in the high speed towing basin at the Naval Surface Warfare Center Carderock Division (NSWCCD). The flexible cylinders are approximately neutrally buoyant and have an initial length of 152 m and radii of 0.45 mm and 1.25 mm. The first objective for this experiment is to evaluate the streamwise development of wall shear stress (τw) and momentum thickness (θ) in axisymmetric turbulent boundary layers using drag measurements at 3.1, 5.2, 9.3 and 14.4 m/s for comparison to existing data. The second and primary objective for this experiment is to determine the streamwise development of the axisymmetric boundary layer flow and to evaluate relevant boundary layer parameters at 3.8, 7.7, 12.9 and 15.4 m/sec using SPIV images acquired over the entire length of the cylinders. Drag measurements reveal that the wall shear stress is large and that the momentum thickness grows slowly when compared to flat plate boundary layers. The velocity field data shows that the boundary flow remains turbulent over the entire length of the flexible cylinder and that the turbulent profile is different from that of flat plate boundary layers.

Vortex generator jets (VGJs) have been found to be an effective method of active separation control on the suction side of a low pressure turbine (LPT) blade at low Reynolds numbers. The flow mechanisms responsible for this control were studied and documented in order to provide a basis for future improvements in LPT design. Data were collected using a stereo PIV system that enabled all three components of velocity to be measured.

A burner for investigating lean stratified premixed flames propagating in intenseisotropic turbulence has been developed. Lean pre-mixtures of methane at differentequivalence ratios are divided between two concentric co-flows to obtain annularstratification. Turbulence generators are used to control the level of turbulence intensityin the oncoming flow. A third annular weakly swirling air flow provides the flamestabilization mechanism. A fundamental characteristic is that flame stabilization doesnot rely on flow recirculation. The flames are maintained at a position where the localmass flux balances the burning rate, the result is a freely propagating turbulent flamefront. The absence of physical surfaces in the vicinity of the flame provides free accessfor laser diagnostics.Stereoscopic Planar Image Velocimetry (SPIV) has been applied to obtain the threecomponents of the instantaneous velocity vectors on a vertical plane above the burneroutlet where the flames propagate. The instantaneous temperature fields have beendetermined through Laser Induced Rayleigh (LIRay) scattering. Planar Laser InducedFluorescence (PLIF) on acetone has been used to calculate the average equivalence ratiodistributions. Instantaneous turbulent burning velocities have been extracted from SPIVresults, while flame curvature and flame thermal thickness values have been calculatedusing the instantaneous temperature fields. The probability distributions of thesequantities have been compared considering the separate influence of equivalence ratiostratification and turbulence.

导管导丝摩擦力测试仪根据《YY/T1536-2017非血管内导管表面滑动性能评价用标准试验模型》、《TCAMDI021—2019一次性使用亲水涂层导丝》研发。是针对医用人体内、外导管、导丝摩擦力性能指标测试开发的一款测试仪器

应用立陶宛Ekspla公司的偏振分辨振动和频光谱测量系统（SFG-VS）对寡核苷酸对层状阳离子脂质双层膜的腹层吸附过程进行了实验研究和理论分析。

采用立陶宛Ekspla公司的由脉冲皮秒激光器PL2251-50和皮秒参量激光器PG401构成的振动和频光谱测量系统，对纤维素样品进行的测量分析揭示了纤维素表面层结构。