漩涡流动

才用LaVision公司特色的DaVis软件平台构成的完整粒子成像测速（PIV）系统对直喷柴油发动机中多漩涡流动进行了测量和分析

旋涡振荡器是利用偏心旋转使试管等容器中的液体产生涡流，从而达到使溶液充分混合之目的。该仪器特点是混合速度 快、彻底、液体呈旋涡状能将附在管壁上的试液全部混均，适用于一般试管、离心管等容器内液体的混合均匀，对于一些难溶解的药物，染色液等也甚易混匀，效果显著。

用PIV方法实验研究了5.5米宽，13.5米长水槽内浅表湍流，剪切流动中大尺度漩涡结构的产生和消失机理。

采用LaVision的图像采集和处理软件平台DaVis 8.4，图像增强器IRO，四台sCMOS相机，四套长工作距离显微镜和两台激光器，构成了构成了一套层析显微PIV和甲醛平面激光诱导荧光（CH2O PLIF)测量系统，并利用这套系统研究了预混漩涡火焰中的熵输运

以寒鸦为测试对象。在风洞中，采用LaVision公司的时间分辨2D3C立体PIV测量系统，对开槽翼尖的多核漩涡对鸟类滑翔和扑翼飞行的支撑作用进行了研究。实验装置包括一台英国Litron公司的LDY304PIV高重复频率激光器，两台Imager pro HS 4M型高速相机，和DaVis8.4软件平台构成。

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。

采用LaVision公司的时间分辨粒子成像测速系统，对水模拟发动机模型中流场的涡流和滚流两种流动形态进行了测量和研究。

涡流涂镀层测厚仪分体N1型探头，检测非磁性金属基体上非导电的绝缘覆盖层的厚度(如铝、铜、锌、锡上的橡胶、塑料、油漆、氧化膜等)。本仪器能广泛地应用在电镀、防腐、化工、汽车、造船、轻工、商检等检测领域。是材料保护配备的仪器。满足JB/T 8393-1996 磁性和涡流式覆层厚度测量仪。

我们扩展了在中性浮力颗粒悬浮的Taylor-Couette流中已知的流动转换，通过在半径比η = 0.917和长径比Γ = 21.67的几何形状中访问更高的悬浮雷诺数(Resusp ～ O(103))。通过流体可视化实验研究了几种颗粒体积分数(0 ≤ φ ≤ 0.40)下的流动转换，这些实验中流体由旋转的内缸驱动。尽管有效斜率更高，但我们观察到存在非对称的图案，例如旋涡，存在颗粒的情况下。我们实验的一项新发现是方位局部化的波动涡流，其特征在一些本来是轴对称的Taylor涡旋中存在波状。这种流动状态的存在表明，除了已经被确认的颗粒不稳定性效应外，它们还可以抑制不稳定性的增长。颗粒悬浮液中对应于高阶转换的流动拓扑似乎与单相流中观察到的拓扑相似。然而，一个关键区别是在更高颗粒负载下出现的第二个不协调频率的出现减少了，这可能对混沌的发生有影响。同时进行的扭矩测量使我们能够估计努塞尔数(Nuω)、Taylor数(Ta)和相对粘度(χe)之间的经验比例关系：Nuω∝Ta0.24χe 0.41。Ta的比例指数与颗粒负载无关。显然，颗粒不会触发在内外缸之间的角动量传递的性质上的定性变化。

使用时间分辨三维颗粒轨迹测速术(tr-3-D-PTV)研究在密度流体中振荡的重质量摆的涡 shedding 拓扑结构。实验系列涉及八个不同的固体到流体质量比 m? 在[1.14,14.95]范围内，并对应雷诺数高达Re～O(104)。摆的振荡周期严重依赖于m?。幅度衰减和振荡频率之间的关系是非单调的，在m?≈2.50时有最佳阻尼效果。此外，实现了一种使用涡量幅值等值面的数字物体跟踪(DOT)方法来分析涡旋结构。对于各种质量比 m?，观察到类似的涡 shedding 拓扑结构。我们的观察结果表明，首先，在摆的尾迹中形成了一个涡环。不久之后，初始涡环分解成两个明显可区分的大小相似的结构。其中一个涡旋留在摆的圆形路径上，而另一个涡旋则分离、向下传播，并最终消散。第一个涡旋的 shedding 时间和其初始传播速度取决于 m? 和球形重物赋予的动量。研究结果还表明，在 Strouhal 数基础上的理论涡 shedding 时间尺度与实验确定的涡 shedding 频率有很好的一致性。

采用LaVision的时间分辨激光诱导荧光火焰分析系统FlameMaster-TR和2D3C时间分辨立体PIV测速系统，对应变速率、局部熄灭和流体力学不稳定性对附着和上升涡流火焰过渡的影响进行了实验测量研究。

采用LaVision公司的IRO和CCD相机构成的增强型CCD相机系统，对CH*的自发荧光图像进行了测量，研究了N2和CO2稀释对C3H8/O2混合气在涡流管式火焰燃烧器中的燃烧特性的影响。

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.

The wake behind a simpli¯ ed model of a generic aircraft (the SWIM model) is measuredin the Low Speed Low turbulence wind tunnel (LSL) at Delft University of Technology.Two measurement techniques have been used in order to qualitatively and quantitativelymeasure the wake, i.e. stereoscopic particle image velocimetry (Stereo PIV) and a 5 holeprobe (5HP). Furthermore balance measurements have been carried out over a range ofcon¯ gurations for later comparison purposes. The goal of the wake measurements is togive a comparison between the two measurement techniques.The 5HP measurements are processed using a windows based program called PressureField Visualisation. This program calculates vector ¯ elds from the input pressure dataand has several exporting options. The Stereo PIV measurements are correlated usingDaVis 7.3 using a window size of 16 x 16 pixels with 50% overlap.

We report particle image velocimetry measurements of the collision of a vortex ring with a heatedwall kept at constant temperature. We consider the case when both the vortex ring and the thermalboundary layer generated by the vertical heated wall are stable and laminar prior to any interaction.The impingement process can be divided into two parts. sid A ring-driven stage, where the vortexring grows in diameter while approaching the wall and therefore it sweeps progressively anincreased surface on the wall. siid A boundary layer-driven stage, where the vortex ring movesupward due to the thermal convective motion generated by the heated wall. In some cases, thehead-on collision triggers the ring’s azimuthal instability as revealed by the formation of vorticalstructures arranged on a wavy starlike pattern and confirmed by flow visualizations. A singlecollision generates important velocity gradients and shear stresses along the wall accompanied withthe creation of local vorticity normal to the vertical heated wall. Peak wall shear stresses occur nearthe point of impact of the vortex ring core.

The trajectory of the tip vortex of a reduced-scale, 1 m diameter, four-bladed rotor during hoveris studied using vortex methods combined with a center of mass analysis approach. The objectiveis to develop analysis techniques capable of accurately characterizing the dynamical features of theunsteady wake produced by rotorcraft during hover, descent, ascent and forward flight conditions.Measurements of all three components of the velocity field are acquired using a stereo PIV systemsynchronized to capture up to 260◦ wake age of the vortex with 10◦ offsets during hover conditions.The nominal operating condition of the rotor is at a blade loading of CT / = 0.0645 and a rotationalspeed of 1240RPM, corresponding to Rec = 180,000. An area encompassing the 95% confidenceregion for the vortex jitter reveals a noticeable anisotropic, aperiodic pattern over all wake ages,which has not been previously observed. The principal axis of the vortex jitter also appears toalign itself perpendicular to the slipstream boundary. An accurate characterization and predictionof the trajectory of the individual tip vortices can significantly enhance the ability to design rotorsto meet specific performance targets such as reduction in fuselage vibrations, noise scattering andmaneuvering noise as well as an alleviation in the resuspension of particles during brownout

前处理称取 混匀的火锅底料样品 2g （精确至 0.01g ）至 50mL 离心管中 ，依次加入已知浓度的标准 品和内标溶液 、5ml 0.1mol/L HCL 溶液 、5 ml 乙腈 ，涡旋 混合 2min ，加入 10ml 正己烷，漩涡 正己烷，漩涡 30s ，振荡提取 30 min 。以 10000r/min 转速离心 3min, 弃去正己烷层 ，过 Bond Elut Plexa PCX (60mg,3ml) 固相萃取柱净化.LC-MS/MS液相色谱柱为 亚二微米 C18,2.1x50mm。流动相 A :水（含0.1%体积比的甲酸),B:乙腈,柱温30℃；进样量 4µ L，流速为0.3 mL/min.

As part of the FARWAKE project, subtask 2.1.1, wake vortex flow experiments are performed using the PIV measurement technique in a water tank. The wake generating model consists of a simple wing/flap model that can be equipped with water jets to simulate propulsion effects. The model was tested at a speed of 3m/s and two angles of attack: 0and 6. Chord Reynolds number of approximately 225.000 and Vortex Reynolds numbers of approximately 150.000 and220.000 were obtained during the tests. The main objective of the present study is to investigate the influence of a jet on the flap end vortex and the wake vortex formation. The investigation focuses on the direct influence ofthe jet on the flap end vortex and the (merged) vortex characteristics in the near to mid field. The main vortex characteristics addressed in this report are: the vortex trajectory, the maximum tangential velocity, the peak vorticity and the vortex core radius. The vortex information is obtained from Stereo-PIV experiments performed in a fixed plane perpendicular to the towing direction. The measurements return the 3 components of the velocity in that plane and the streamwise component of the wake vorticity. A submergiblemoving camera system is used in order to keep the moving vortex in the field of view during the vortex downward motion.

This study deals with the flow motion over the so-called rolling-grain ripples which are generated by water oscillations above a sand bed. We focus our efforts on quantifying by means of laboratoryexperiments and numerical calculations the morphology and the dynamics of transient flow patterns. We report, for the first time, on the formation of an unsteady pattern with closed streamlines ~we call it ‘‘eddy’’! above rolling-grain ripples using flow visualizations and particle image velocimetry(PIV) measurements. This structure appears in the ripple trough during flow reversal and scales with the ripple wavelength. The experimental results are in qualitative agreement with the perturbative flow solution calculated by Vittori in 1989. Even if the relative ripple amplitude is not small in the experiment the perturbative expansion at the first order gives an accurate description of the flow dynamics.

Reducing the deleterious effect of Vortex Induced Vibrations (VIV) in marine risers is animportant task for ocean engineers and many competing factors exist in the design ofVIV suppression devices. This thesis explores the experimental minimization of the dragforce and the disruption of v0l1ex formation by utilizing VIV suppression devices.Two series of tests are conducted-both utilizing separate testing designs. The first testsare the flexible cylinder experiments, detailed in Chapter 2, which determine the dragforce and vibration amplitude of numerous, original testing configurations. The secondseries of tests are the rigid cylinder, PIV experiments, detailed in Chapter 3. These testsmeasure both the drag force on the cylinder and the oscillating component of the liftforce, the latter of which is a good indication of v011ex formation. The Chapter 3 testsalso image the test section wake-providing helpful insight into the physical process ofvortex formation.In brief, this thesis presents a detailed description and results of the two series of originalVIV suppression tests. Many original configurations are tested, and the results arecontained herein.

A coaxial jet was actively controlled by a MEMS-fabricated micro flap actuator nozzle. The effect ofdifferent control modes on secondary azimuthal instabilities and the evolution of streamwise vorticeswere investigated by applying stereoscopic PIV to the cross-stream plane of the jet. Forcing withnon-symmetric modes, in particular the least-stable helical mode, accelerates the evolution of thestreamwise vortices through the enhancement of azimuthal instabilities. Although forcing is appliedto the outer shear layer of the outer jet, the control effect is most pronounced in the inner shear layerof the inner jet. Unlike in the natural jet, streamwise vortices appear in the inner shear layer of thecontrolled jet. For forcing with the fundamental axisymmetric mode, a Strouhal number of the orderof unity maximise the azimuthal instabilities and hence the counts of the streamwise vortices. Thepresent result is in accordance with our previous experimental findings in the longitudinal plane,where the evolution of the primary vortices and mixing between the inner and the outer jets wereexamined through 2D-PIV and PLIF (Kurimoto et al., 2004, Active control of coaxial jet mixing witharrayed micro actuators. Transactions of the Japanese Society of Mechanical Engineers, pp. 31–38.)This emphasises the connection between primary and streamwise vortices and their significance in themixing enhancement process. It is also found that the azimuthal wavelength under the present controlscheme is almost the same as that of the natural jet and independent of the streamwise position.

微气象方法在陆地生态系统之上的微量气体通量测量中越来越重要。其能够在较长时间内测量较大尺度的平均气体通量，并具有较高的时间分辨率。应用最广泛的是涡动相关法(EC)，其典型可测定面积(或“通量足迹”)可达几公顷。但由于缺乏快速响应的气体分析仪和较低的信噪比，仍然局限于测定少数气体种类。此外，EC对小分子的大气成分如氧化亚氮的适用性往往受到高功率消耗的限制。涡流累积是另一种湍流交换测量系统的代表，在1990年Businger和Oncley提出了一种使用恒定流量涡流积累的“松弛”版本(松弛涡流积累，REA)。近年来，光腔衰荡光谱(CRDS)分析仪的发展为小分子大气组分的浓度测量提供便利，特别为通过REA技术测量气体流量开辟了机会。虽然通过慢响应分析仪进行气体分析相对容易，但开发一种精确、可靠且耐用的快速响应空气采样系统仍然是一种技术挑战。 为了可靠地估算区域一氧化二氮的排放，监测全区域的N2O通量具有重要意义，通常传统的EC和REA系统都可以提供这种类型的数据。然而，EC系统测定时初始成本高，能耗高，而且运输到偏远地区以及现场为系统供电相对困难。此外，为了使用EC系统测量陆地生态系统的温室气体通量，目前还没有快速响应气体分析仪可满足条件。然而，对于REA系统，光腔衰荡光谱仪(例如Picarro G2508)可以同时用于分析水蒸气、甲烷、二氧化碳和一氧化二氮。本文提出了一个新的REA系统。该系统能可靠地测量多季节变化下的区域CO2、N2O、CH4和水汽的通量，并对其在2018和2020年季节变化下的测定性能进行了评估。

采用LaVision的两台HSS6型CMOS高速相机，工作在4kHz重复频率。在DaVis 8.2软件平台控制下。构成了一套时间分辨高帧频平面激光诱导荧光（PLIF)和时间分辨粒子成像测速系统（TR-PIV)。利用该系统对处于热声双稳态状态的湍流旋涡火焰进行了高速OH-PLIF和PIV的同时测量。

磁力搅拌器利用了磁场和漩涡的原理，将沉入搅拌子的待搅拌液体之容器放置于磁力搅拌器的底座上，当磁力搅拌器通电后，底座附近产生一个旋转的磁场带动搅拌子成圆周循环运动，进而在容器液体内形成一个漩涡，从而达到搅拌液体的目的。

本研究考察了一个双稳湍流旋转火焰中的复杂流场，其中火焰不规则地在离开的M形和附着的V形之间交替。流场由于火焰形状转换在不同的时间尺度上出现各种类型的间歇性动力学。为了正确识别、分离和时间上解析这些动态组分，通过将多维数据序列的最大重叠离散小波包变换（MODWPT）与常规瞬态POD相结合，开发了一种新的多分辨率proper orthogonal decomposition（MRPOD）方法。特别注意选择小波滤波器、分解水平和重构带宽以实现可变的频谱通带和足够的时间分辨率。当应用于双稳旋流火焰中高速三分量速度场测量的数据序列时，MRPOD能够隔离通常被合并为单个POD模式的频率组分，对于即使是弱的和高度间歇性的动力学，增强了空间/时间的一致性。由于改进的频谱纯度，一系列先前未知的动态被揭示出来，其中包括预旋涡核（PVC）和热声（TA）不稳定性等已被描述的不稳定性。特别是，在火焰形状转换期间，发现非周期切换模式只与先前确定的转移模式相耦合，在倒流和燃烧器进口附近产生显著的修改，这是一个已知会影响PVC增长率的区域。在M-V转换期间，TA振荡驱动反复的火焰再附着，最终稳定为V火焰。但是，持续高的TA振幅似乎并不一定预示着这种转换的开始。发现了PVC的更高阶谐波以及TA调制PVC动力学的证据，它们也表现出双峰行为：虽然保持其特征频率，但这些不稳定性在V-或M火焰期间才能发挥作用，且只能具有单螺旋或双螺旋结构。

Detailed schlieren and laser lightsheet visualizations of the near wake of micro vortexgenerator (MVG) revealed large structures that were different from those of the undisturbedturbulent boundary layer. These structures were attributed to the rapid breakdownof the primary trailing vortex pair. The breakdown was thought to arise from a cylindricalKelvin–Helmholtz-like instability surface. The structures appear to be hairpin or ring-likein nature that showed eruptions into the freestream flow, entraining it.

中心级旋流燃烧可以有效地降低NOx排放。但是，这种复杂的燃烧场容易产生大规模的相干结构，例如旋转涡核和中心涡核（CVC）。本研究主要利用10 kHz高速CH化学发光（CL）、20 kHz颗粒图像测速仪（PIV）和CH2O平面激光诱导荧光（PLIF），在高温高压下研究中心级旋流喷雾燃烧器中CVC对流场和火焰的影响。对于试验火焰，CH CL和CH2O PLIF火焰都是三叉形状的，并且火焰动力学的中心部分表明了CVC结构。对于分层火焰，在燃烧器中心线附近的一个强旋涡带区域内存在CVC结构。适当正交分解（POD）模式的分析表明，CVC的运动主要是摆动，其次是进动。同时诊断表明，CVC的吸入导致CH2O从剪切层输送到燃烧器的中心区域。总体而言，CH2O信号主要分布在两个正的速度区域，即主燃气和中心涡核周围。利用CVC对自由基输运的作用是改善燃烧器混合，例如温度分布的潜在方法。

Vortex generator jets (VGJs) have proven to be effective in minimizing the separation losses on low-pressure turbine blades at low Reynolds numbers. Experimental data collected using phase-locked particle image velocimetry and substantiated with a hot-filmanemometer were used to answer fundamental questions about the influence of VGJs on a separated boundary layer. The data were collected on the suction surface of the Pack B blade profile, which has a non-reattaching separation bubble beginning at 68% axialchord. Two VGJ pulse histories were created with different frequencies, jet durations,and duty cycles. The mechanisms responsible for boundary layer separation control wereshown to be a combination of boundary layer transition and streamwise vortical structures. Jet duration and relaxation time were important VGJ characteristics in determining the extent of control. The unsteady environment characterisitic of the low-pressure turbine section in a gas turbine engine effectively reduces the time-averaged separation zone by as much as 35%. Upstream blade rows create unsteady flow disturbances (wakes) that transition the flow. This transitioned flow propagates downstream, re-attaching the separation bubbles on the subsequent blade row. Phase-locked PIV and hot-film measurements were used to document the characteristics of this separation zone when subjected to synchronized unsteady wakes and VGJs. The phase difference between VGJ actuation and the wakepassing, blowing ratio, and VGJ duration were optimized to achieve the greatest timeaveraged control of the separation zone. The experimental data were used to identify the important characteristics of the wake/jet interaction. Phase-locked PIV measurements were taken to isolate the wake event.

甲醛以及甲醛缓释剂作为杀菌防腐剂被广泛添加于化妆品中。甲醛对人体会产生刺激、致畸、过敏等伤害，具体表现为头晕、浮肿、色斑等。 该前处理方法，采用柱前衍生，二氯甲烷阻断衍生的方法，解决检测过程中甲醛缓释剂释放甲醛而影响原有的游离的甲醛含量测定的困难。且实验过程简单，只需要用漩涡混合器，进行漩涡混合即可，无需其它的前处理仪器。操作方便快捷，省时省力。

甲醛以及甲醛缓释剂作为杀菌防腐剂被广泛添加于化妆品中。甲醛对人体会产生刺激、致畸、过敏等伤害，具体表现为头晕、浮肿、色斑等。 该前处理方法，采用柱前衍生，二氯甲烷阻断衍生的方法，解决检测过程中甲醛缓释剂释放甲醛而影响原有的游离的甲醛含量测定的困难。且实验过程简单，只需要用漩涡混合器，进行漩涡混合即可，无需其它的前处理仪器。操作方便快捷，省时省力。