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。

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。

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.

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。

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

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。

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.

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.

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.

针对传热学三类边界条件目前常见的定义，本文从导热、对流和辐射三种传热机理出发介绍了三类边界条件的物理意义及其拓展。另外，本文重点介绍了三类边界条件更直观的温度形式的定义，以及这些边界条件温度形式在热物性测量中的实际应用。

在传热学第三类边界条件下进行的热物性测试方法中，如Angstrom法、ISO 22007-3温度波法和ISO 22007-6温度调节比较法，会要求边界温度严格按照正弦波形式进行变化，但采用正弦波加热电流方式的现有技术很难实现准确稳定的正弦温度波输出，且给测量带来较大的随机误差。为此本文提出了相应的解决方案，方案的核心是采用具有远程设定点功能的PID控制器，并配套外置正弦波信号发生器或过程校验仪，通过不断改变PID控制器设定值来实现正弦温度波的准确输出。

"文中介绍了采用PerkinElmer® Clarus® 600 GC/MS儿童玩具胶涂层中的乙二醇进行快速筛查，结果：该方法无论在样品制备，还是色谱分析方面都非常简单便捷。"

采用Artium公司的相位多普勒粒子干涉仪对核反应堆中大型工业安全喷雾的液滴粒径和速度进行了测量，并采用数值模拟方法分析了简化喷雾边界条件对其特性的影响。

在宠物食品行业中，湿粮作为猫咪和狗狗日常饮食的重要组成部分，其包装的安全性与功能性直接关系到产品的保质期、运输效率及消费者的使用体验。其中，包装袋内层的摩擦系数是一个关键指标，它不仅影响着湿粮的封装紧密度，还直接关系到开封的便捷性以及包装袋在自动化生产线上的表现。本文将详细介绍宠物湿粮包装袋内层摩擦系数的检测方法，并附带详细数据以供参考。

显微拉曼在石墨烯表征中的应用石墨烯是目前发现的最薄、强度最大、导电导热性能最强的一种新型纳米材料。就石墨烯材料及其器件的研究而言，鉴别 石墨烯层数 以及量化其无序性的影响是至关重要的，而显微 拉曼光谱，是用于表征上述两种性能的便捷又可行的方法。

大脑中的铁沉积是正常衰老的一个特征，尽管在包括阿尔茨海默氏症在内的几种神经退行性疾病中，铁沉积的速度比年龄匹配的对照组要快。利用激光剥蚀电感耦合等离子体质谱成像技术，我们在此提出了一项初步研究，定量评估了阿尔茨海默病和对照组额叶皮层石蜡包埋切片中白质和灰质铁的含量。使用磷成像指示白色/灰色边界问题,我们发现,在阿尔茨海默氏症的大脑灰质中铁的含量明显比控制变量组的大,这可能是指示在这个脆弱的大脑区域铁的稳定性较差,或为应对慢性神经退化增加炎症提供了证据。我们还观察到额叶皮层白质内铁含量增加的趋势，这可能表明在髓鞘完整性丧失之前铁代谢紊乱。考虑到大脑中过量铁的潜在毒性，我们的结果为不断发展新的磁共振成像方法提供了有力的支持证据，以评估阿尔茨海默病中白质和灰质铁积聚。