Program

Program at a Glance ( Final Technical Program )

Short Course on 3D PIV, Busan, June 22nd, 2017

  1. The short course on 3D PIV is intended for researchers who currently use 3D PIV systems as well as those who intend to practice these types of measurements in the future. It is assumed that the participant has basic background knowledge of the PIV technique and/or has practiced it.

    Course program (9:00 - 17:30)

    1. 1)Introduction on 3D- and 4D-Particle Imaging and Velocimetry (Fulvio Scarano,TU Delft)
    2. 2)Volume illumination (Chris Willert, DLR Cologne)
      Sources (Lasers and LED), modes of operation (CW, double pulses, high-rep), illumination setup, collimation, multi-pass, reflection management, polarization
    3. 3)Seeding particles and conditions (Fulvio Scarano, TU Delft)
      Seeding air flows, water flows, combustion and other fluids, fluorescence. Rules for seeding concentration and particle image density
    4. 4)Imaging (Chris Willert, DLR Cologne)
      Mie scattering and reflection, geometrical and diffraction imaging, cameras types (CCD, CMOS, sCMOS), pixel-locking, SNR, 3D imaging aperture, system synchronization
    5. 5)Brief survey of existing 3D PIV techniques (Stefano Discetti, UC3M)
      3D-PTV, Holographic PIV, Digital Defocusing 3D PTV, Scanning light sheet, photogrammetry, Tomographic PIV, Astigmatism 3D PTV, Plenoptic 3D PIV, Synthetic Aperture 3D PIV etc.
    6. 6)Working principles of Tomographic PIV (Stefano Discetti, UC3M)
      Image/object space calibration 3D, image preprocessing methods, calibration correction (Volume-Self-Calibration), Optical Transfer Function detection and calibration (OTF)
    7. Lunch break
    8. 7)Demonstrations of 3D PIV systems from exhibitors
      LaVision, DanTec, Beamtech
    9. 8)based object reconstruction and motion analysis (Matteo Novara, DLR Göttingen)
      3D reconstruction (MART), 3D cross-correlation and validation, advanced motion estimation algorithms (sliding average correlation, FTC, FTEE), Motion Tracking Enhancement (MTE) for double-frame and time-resolved recordings (SMTE), hybrid tomographic and tracking methods (pseudo-tracking, Tomo-3D-PTV)
    10. 9)Particle based object reconstruction and motion analysis (Daniel Schanz, DLR Göttingen)
      Iterative Particle Reconstruction (IPR), multi-pulse and time-resolved reconstruction with Shake-The-Box (STB), particle trajectories estimation techniques (temporal filtering along tracks, velocity-acceleration estimation, outliers detection (validation)
    11. 10)3D data post-processing (Andreas Schröder, DLR Göttingen)
      One- and multi-point statistics, vector field operators for 3D PIV (spatial derivatives, vortex detection), data assimilation techniques on 3D PIV and Lagrangian Particle Tracking (LPT) (solenoidal filtering, NavierStokes-Regularization (e.g. FlowFit, VIC +), pressure from PIV and LPT
    12. 11)Panel of applications to aerodynamics and turbulent flows, perspectives and closure remarks (Andreas Schröder, DLR Göttingen)

Plenary Lectures

  1. 1. Prof. Carl Meinhart(University of California Santa Barbara, USA)

    Title
    “Micro-PIV: The First Twenty Years”
    Abstract
    It has been 20 years, since the first developments of micron-resolution Particle Image Velocimetry (micro-PIV). Since that time, there have been many variations and extensions of the technique, such as: confocal imaging, evanescent illumination, 3D techniques, and many others. Applications of micro-PIV have led to increased understanding of fundamental microscale phenomena, behavior of cells and biological organisms, as well as advances in commercial microfluidic devices.
    So where do we go from here? Have we reached the fundamental limitations of micro-PIV, or are we on the verge of further advances?
    To answer some of these qustions, recent work at UCSB will be presented, where we combine surface plasmonics and near-field optics to develop next generation velocimetry tools.
  2. 2. Dr. Christian Willert(DLR, Germany)

    Title
    “The role of particle image velocimetry in industrial R&D - the tricky balance between customers' wishes, cost and the limits of physics”
    Abstract
    Already from the point of view of making fluid flows “visible” and quantifiable the particle image velocimetry technique has made substantial impact on experimental fluid mechanics and associated engineering fields. After three decades of continuous and still ongoing development, the technique nowadays offers access to fully resolved velocity field data, both in space and time, and is supported by a thorough mathematical-theoretical background, which allows a characterization of its performance and uncertainties. Yet, the use of the technique – in particular to its full capacity – continues to play a secondary role in applied industrial research and is often side-lined with respect to conventional “established” point-wise measurement techniques. In many PIV applications the acquired PIV data is mainly used for the “validation” of numerical methods, leaving the full potential provided by the spatio-temporal resolved PIV data untapped. The presentation will introduce several examples of PIV applications in industrial R&D, mainly from the turbomachinery sector involving transonic compressors and high pressure combustion, and illustrates a variety of challenges and compromises faced in making PIV (and other optical measurement techniques) possible in rough operating environments.
  3. 3. Prof. Fulvio Scarano(Delft University of Technology, Netherlands)

    Title
    “Particle Image Velocimetry reinvented”
    Abstract
    Particle image velocimetry has deployed its full potential in the past decades and is nowadays the technique of choice when dealing with experimental fluid mechanics. Despite its success among research laboratories, PIV systems remain relatively complex to operate requiring much skills, expertise and time, often not available at industrial sites.
    Researchers using PIV must face frustration and thrill when adjusting plane of focus, scheimpflug angle, camera aperture, or when avoiding background reflections and improve optical access. Experiments become increasingly complex when dealing with large-scale problems due to the limited spatial scalability of PIV. Meticulous work is needed to put together several measurement regions covering a large measurement domain not achievable otherwise.
    The work presented in this lecture is inspired to PIV versatility. The lecture presents recent innovations leading to a technique with the same principles as PIV, but significantly different in how experiments are planned, conducted and exploited.
    The main pillars for reinvention are the Helium Filled Soap Bubbles, the Tomographic imaging architecture, the Coaxial Volumetric Velocimeter, the introduction of Robot Manipulation and advanced 3D-PTV analysis (Shake The Box).
    The talk also illustrates the potential of the resulting approach by sharing the experience gained from a number of applications to large-scale aerodynamic measurements.
  4. 4. Prof. Koichi Nishino and Taishi Yano(Yokohama National University, Japan)

    Title
    “Space experiments and application of PIV techniques for the study of instability mechanisms of thermocapillary convection”
    Abstract
    Instability mechanisms of thermocapillary convection in liquid bridges of high Prandtl number fluids have been studied in microgravity environment on the International Space Station (ISS). Flow visualization and PIV techniques are exploited to extract vital information for understanding instability mechanisms. All apparatuses on ISS were remotely controlled from the space center at Tsukuba, Japan. Three-dimensional PTV with modified trajectory tracking algorithm was used to capture 3-D flow structures associated with propagation of hydrothermal waves. Tomographic PIV was also used to extract spatially-resolved information on the 3-D flow structures. The results were compared with those predicted from the linear stability analysis and discussed in light of the effect of interfacial heat transfer on the instability mechanisms.

Keynote Lectures​

  1. 1. Prof. Dana Dabiri(University of Washington, in Seattle, USA)

    Title
    Design & Implementation of a 3D-PTV System
    Abstract
    It is the wish of experimental fluid dynamicists is to be able to measure complex, three-dimensional turbulent flow fields globally with very high spatial and temporal resolution. Towards this goal, several volumetric velocimetry methods have been developed that are worth noting for allowing for 3D measurements: defocusing PIV, holographic PIV, tomographic PIV, synthetic aperture PIV, and plenoptics PIV. In this presentation, we introduce a volumetric PTV methodology that can be used for either a single camera or multi-camera system. The single camera hardware setup is based upon that developed by Willert & Gharib. Here we are able to identify larger number of particles by color-coding the pinholes in order to separate particle exposures from different pinholes, though this step is clearly not needed for the multi-camera system, as each camera images obtains separate exposures of the particle field. In addition, an algorithm is developed that can identify overlapped particles, thereby allowing for identification of larger number of particles. A calibration-based triangulation method is used to identify triplets. A vision-based algorithm is developed to pair particles. Finally, a PTV outlier detection method is developed based on the universal PIV outlier detection method by Westerweel and Scarano. These developed algorithms, though developed for the DDPIV setup, can easily be used for other multi-camera configurations. To test the ability of our methodology, we implemented this methodology to a micro-scale 3D-PTV system, and used it to image flow behind a micro-scale backward-facing step, and within a micro-channel flow. In addition, we also implemented this methodology to a macro-scale 3D-PTV system and used it to image flow behind a backward-facing step. Details of our work can be found in Tien et al., Grothe et al., Duncan et al., Lei et al., and Tien and Dabiri.
  2. 2. Prof. Stefano Discetti(Universidad Carlos III de Madrid, Spain)

    Title
    Adverse-pressure-gradient turbulent boundary layers: flow organization and high-resolution statistics
    Abstract
    The efficiency of airplanes, ships, compressor, turbines, and many other devices, is generally bound by the behavior of the turbulent boundary layer (TBL) under the effects of pressure gradients, which, if unfavorable, might trigger flow separation with consequent loss in performance. Notwithstanding with its relevance, the effect of the adverse pressure gradient (APG) on the turbulent boundary layer is still challenging to be predicted due to the large number of parameters involved. In this work a comparative study employing PIV, hot-wire anemometry and numerical simulations is presented. PIV measurements are carried out for Re_τ up to 4,000 and for different values of the Clauser pressure gradient parameter β to investigate the effect of APG conditions on the outer-layer structures and their interaction with the near-wall region. Multi-point high resolution first and second-order turbulent statistics are extracted via ensemble correlation. A modal analysis with Proper Orthogonal Decomposition is carried out to infer on the contribution of the coherent structures to the Reynolds stresses.
  3. 3. Prof. Hyung Jin Sung(KAIST, Korea)

    Title
    Tomographic PIV measurements for flow-structure interaction
    Abstract
    Abstract : The schooling behavior of rigid and flexible NACA0017 airfoils undergoing a heaving motion was experimentally explored using a merry-go-round configuration. Each airfoil was attached to the end of a horizontal support bar whose other end was connected to a freely rotating vertical axis. The axis was forced to undergo a sinusoidal motion in the vertical direction to generate a pure heaving motion of the airfoil. This experimental setup simulates the infinite schooling of airfoils separated by a streamwise distance undergoing in-phase heaving motions. The schooling number was introduced to explain the schooling behavior of the airfoils. A three-dimensional surface of an arbitrarily moving body in a flow field was reconstructed using the DAISY descriptor and epipolar geometry constraints. The surface shape of a moving body was reconstructed with tomographic PIV flow measurement. The originally captured images were separated into the particle and surface images using a Gaussian smoothing filter. The separated particle images were used to reconstruct the particle volume intensity via tomographic reconstruction approaches. Three-dimensional experiments that modeled the flows around a flapping flag, a rotating cylinder and a flapping robot fish tail were conducted to validate the present technique. The flow patterns inside a scaled transparent model of a nasal cavity were measured by tomographic PIV with three-dimensional (3D) geometry acquisition. The complex geometry of the 3D nasal model was acquired by accumulating triangulated 3D particle positions. Certain morphological operations, such as the opening and closing of the nasal cavity, were used to improve the quality of acquired nasal geometry data.
  4. 4. Prof. Hui Hu(Iowa State University, USA)

    Title
    Experimental Investigations of Wind Turbine Aeromechanics and Wake Interferences in Onshore and Offshore Wind Farms
    Abstract
    The recent research progress made in the speaker’s research group on wind turbine aeromechanics and wake interferences among multiple wind turbines sited in onshore and offshore wind farms will be introduced. Experimental studies were conducted in a large-scale Atmospheric Boundary Layer (ABL) Wind Tunnel available at Iowa State University (ISU). An array of scaled wind turbine models were placed in ABL winds with different mean and turbulence characteristics to simulate the scenarios in onshore and offshore wind farms. The effects of the spacing between turbines, turbine array layout, turbine rotation direction, terrain topology of wind farms, and wave-induced base motion for offshore floating wind turbines on their performances and wake interferences are investigated systematically. In addition to measuring dynamic wind loads (both forces and moments) and the power outputs of the wind turbine models, a high-resolution Stereoscopic Particle Image Velocity (SPIV) system was used to conduct detailed, phase-locked, flow field measurements to quantify the characteristics of unsteady wake vortices and wake interferences among the wind turbines sited over a flat (baseline case) and hilly terrains with non-homogenous ABL winds. The detailed flow field measurements were correlated with the measured dynamic wind loads and power output data in order to elucidate underlying physics for higher total power yield and better durability of wind turbines operating in turbulent ABL winds.
  5. 5. Prof. Christian Kähler(Bundeswehr University Munich, Germany)

    Title
    Time-resolved high-resolution 3D PTV investigations of near-wall turbulence
    Abstract
    The three dimensional flow dynamics in the near wall (y+<6) region of turbulent boundary layers subjected to adverse pressure gradient is very complex and 3D time resolved measurement techniques are needed to resolve the flow processes. By using a novel tomographic particle tracking technique (TOMO-PTV) approach it was possible to study the flow dynamics in great detail at Reτ = 5000. It will be demonstrated that this approach can fully resolve mean and instantaneous features of the complex three-dimensional flow down to very near wall distances (~10 μm). From time resolved Lagrangian particle trajectories, statistical information as well as instantaneous topological features of near wall flow features are analyzed. Similar to the zero pressure gradient case (ZPG), it was found that the reverse flow events still occur relatively rarely under the action of the pressure gradient investigated here (only 1% for the combined data sets of 100 000 images) but their spatial extent can become quite large relative to the observations in boundary layers without pressure gradient. Furthermore, instantaneous measurements of reverse flow events show that these events are associated with the motion of low momentum streaks in the near wall region. It is also shown that low momentum turbulent superstructures in the logarithmic region of the turbulent boundary layer flow seem to play a significance role in the generation of reverse flow events. This explains the observation that these reverse flow events appear frequently in groups. Moreover, it was observed that some of the reverse flow events are associated with stream-wise vortices inside low speed streaks. This can be explained by the tilted nature of these vortices with respect to the main flow direction. The results and discussion will serve to better understand the interaction of coherent flow structures leading to reverse flow events.
  6. 6. Prof. Bertrand Lecordier(UMR CNRS 6614 CORIA, University of Rouen, France)

    Title
    Combined planar velocity and scalar measurements for reacting flow investigations.
    Abstract
    The understanding of the combustion-aerodynamics interaction is a challenging aspect of investigation of the reacting flows due to the large span of spatial and temporal scales involved. In the past, despite intensive use of high resolution pointwise measurement techniques to obtain statistical information about the flow properties, temperature field, species concentration..., it had been clearly shown that the unsteady 3D characteristic of turbulent flow and flame interactions makes difficult detailed analysis from averaged measurements. These combustion-aerodynamics interactions induced complex correlation between physical properties which makes simultaneous measurements useful in turbulent combustion research. These aspects have motivated the scientists in the combustion community to consider planar laser diagnostics as soon as the early stage of their availability, but also to contribute significantly to their developments. The interest of 2D measurement to investigate reacting flows has been clearly demonstrated in numerous academic and industrial configurations. One supplementary potential of the laser diagnostics, and then the 2D laser diagnostics is their capability to be combined together. Then more recently, in order to investigate in more details the combustion-aerodynamics interactions, velocity measurements by PIV is often associated with other optical techniques (LIF, LII, flame emission...) of scalar measurement. The simultaneous measurement of two quantities have opened for few years a wide field of investigation, especially by allowing to performed conditioned measurements. The purpose of the present paper is to review the major kinds of combination of 2D velocity measurement with scalar measurements to investigate reacting flows and to show the potential of the laser diagnostic coupling for performing conditioned measurements need for advanced data processing. All these aspects will be illustrated by a selection of examples of advanced data processing specific to the simultaneous measurements for reacting flow.
  7. 7. Prof. Sang Joon Lee(Pohang University of Science and Technology, Korea)

    Title
    In vivo X-ray PIV Measurements of Circulatory Blood Flows
    Abstract
    In-vivo measurement of hemodynamic information of real blood flows in arteries is very important for examining the pathologies of circulatory vascular diseases. Especially in-vivo experiments using animal models are essential for investigating the hemodynamic parameters of cardiovascular diseases (CVDs). To get hemodynamic information of various CVDs, X-ray PIV (particle image velocimetry) technique in which X-ray beam is used as a transmission-type light source was developed. At first, the feasibility of the X-ray PIV technique for measuring blood flows was confirmed through in vitro experiments. Then surface-modified gold nanoparticles and biocompatible CO2 microbubbles were developed as tracer particles of blood flows. The developed X-ray PIV technique was found to have high temporal and spatial resolution to measure real pulsatile blood flows in a nondestructive manner with micrometer resolution. For in vivo X-ray PIV measurements, tracer particles were injected into rat models directly or to the extracorporeal loop connecting the jugular vein and abdominal artery of a rat model. The velocity field information of real pulsatile blood-flows was obtained with varying flow rate and pulsatility. This X-ray PIV would be effectively used to investigate hemodynamic and hemorheological features of blood flows related with CVDs.
  8. 8. Prof. Yingzheng Liu(Shanghai Jiao Tong University, China)

    Title
    PIV measurements of vortex dynamics in wakes and separated flows: Proper orthogonal decomposition and dynamic mode decomposition analysis
    Abstract
    A comprehensive evaluation of Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) was first given in terms of synthetically generated dataset buried with multiple different convective structures; the influence of background 'noise' is also discussed. Subsequently, the wakes and separated flows in several representative configurations are measured using the PIV/TR-PIV systems; the DMD and POD analyses were employed to identify the superimposed energetic flow structures, while the reconstruction using the leading energetic modes clarifies the dominant unsteady behaviors. Further work is performed on a joint POD analysis of the wall-pressure field and the flow field around a blunt plate, which were respectively measured using a microphone array and the PIV; the coupling of the flow structures and the wall-presssure fluctuations is delineated. Finally, an informative introduction is made of the recent efforts on POD-based spatial refinement of TR-PIV realizations using high-resolution non-TR-PIV measurements.
  9. 9. Prof. Nao Ninomiya(Utsunomiya University, Japan)

    Title
    3-D Velocity Measurement of Particles by a Single Camera using Doppler Phase-Shifting Holography
    Abstract
    In order to understand the details of the flow field in the micro- and nano- fluidic devices, it is necessary to measure the three-dimensional velocity under a microscopy. Thus, the development of a new measuring technique for the three-dimensional velocity by a single.
    camera observation is strongly needed. One solution is the use of holography, but it has been known that the resolution in the depth direction is very poor for the commonly used in-line holography. Presently, the Doppler phase-shifting holography has been used for the three-dimensional measurement of particles. This method extracts the signal of a fixed frequency caused by the Doppler beat between the object light and the reference light. Here, the frequency of the Doppler beat is determined by the velocity difference between the object light and the reference light. This implies that the longitudinal velocity of an object can be measured by the beat frequency. At the same time, transverse velocities can also be measured by the ordinary PIV algorithm. In this study, particles are traversed at different speeds and their holography has been observed by a high-speed camera. By extracting only the first order diffraction signal at each beat frequency, three-dimensional velocity measurement of particles has been achieved.
  10. 10. Prof. David Rival(Queen's University, Canada)

    Title
    A discussion on force estimation using Eulerian and Lagrangian frameworks
    Abstract
    In a large variety of fluid-dynamic problems it is often impossible to directly measure the instantaneous aerodynamic or hydrodynamic forces on a moving body. Examples include studies of propulsion in nature, either with mechanical models or living animals, wings and blades subjected to significant surface contamination such as icing, sting blockage effects, etc. In these circumstances, load estimation from flow-field data provides an attractive alternative method, while at the same time providing insight into the relationship between unsteady loadings and their associated vortex-wake dynamics. Historically, classical control-volume techniques based on time-averaged measurements have been used to extract the mean forces. With the advent of high-speed imaging, and the rapid progress in time-resolved volumetric measurements such as Tomo-PIV and 4D-PTV, it is becoming feasible to estimate the instantaneous forces on bodies of complex geometry and/or motion. For effective application under these conditions a number of challenges still exist, including the near-body treatment of the acceleration field as well as the estimation of pressure on the outer surfaces of the control volume. Additional limitations in temporal and spatial resolutions, and their associated impact on the feasibility of the various approaches, are also discussed. Finally, as an outlook towards the development of future methodologies, the potential application of Lagrangian techniques is explored.
  11. 11. Prof. Giampaolo Romano("La Sapienza" University in Roma, Italy)

    Title
    Experimental techniques and phase-discrimination strategies for velocity and size measurements in two phase flows
    Abstract
    The measurement of variables of interest in multiphase flows is rather complex due to the overlapping of many particles, droplets or bubbles in the test region. The problem is even much more complicated when measurements using non-intrusive anemometrical optical techniques are involved, as in Particle Image Velocimetry (PIV), due to the additional presence of tracer particles which must be added to the fluid phase for proper velocity measurements. Specifically, especially in turbulent flows, the most relevant problem is to measure accurately the velocity field of each phase, to allow the computation of cross velocity-size correlation, useful to investigate phenomena of spreading and deposition. To this end, it is necessary to determine with small and known errors the size of single particles (droplets, bubbles), simultaneously to that of the flow phase, when tracers are present. In this presentation, some of the available multi-point experimental techniques used to measure size of spherical and nonspherical particles are described and compared, in order to point out advantages and drawbacks of each one, with a special attention to the evaluation of measurement errors. Measurements are performed in a dedicated apparatus, i.e. a completely transparent tank filled with water (composition and temperature are controlled and changed), in which cathode and anode wires generated oxygen and hydrogen bubbles (the electric variables as also the wire diameter and separation are also controlled and changed). Specifically, two different techniques are used and compared for different parameter configurations: Shadow Imaging (SI) and Interferometric Laser Imaging for Droplet Sizing (ILIDS) or Global Phase Sizing (GPS).
  12. 12. Prof. Jun Sakakibara(Meiji University, Japan)

    Title
    PIV study on flow in eye
    Abstract
    Anterior chamber, which is a gap between cornea and lens in our eye, is filled with water. This water is usually stationary, but may have rapid flow under cataract surgery, which is an operation to replace opaque lens with artificial lens, and consequently the interior surface of cornea may be influenced by the fluid forces applied. We measured velocity distribution of such flow field simulated in pig’s eye by use of stereo PIV, and estimated shear stress. We also studied flow in vitreous chamber, which is a space between the lens and retina, after an operation called vitreous surgery that replaces original gel filling the chamber with water. Fluid velocity field was measured by two-component PIV or three-dimensional PTV and shear stress acting on the retina was estimated.
  13. 13. Dr. Andreas Schröder(DLR, Germany)

    Title
    Dense 3D Lagrangian Particle Tracking using Shake-The-Box – A new key for experimental fluid mechanics
    Abstract
    The novel 3D Lagrangian Particle Tracking method “Shake-The-Box” (STB) is able to extract particle trajectories from volumetric flow measurements at unprecedented numbers. It delivers accurate data on position, velocity and acceleration (material derivative) along these tracks. Subsequently, data assimilation approaches can be applied to the dense and scattered input data. An example is the “FlowFit” (FF) method, which uses Navier-Stokes-constraints for an interpolation of the flow field onto a regular grid in order to gain the full time-resolved velocity gradient tensor and pressure field with high spatial and temporal resolution.
    The STB method can be applied as well to short recording sequences, acquired with multi-pulse techniques, allowing investigating high-speed flows at Reynolds numbers relevant for research in aerospace engineering.
    Recent developments of STB and FF will be presented here, along with data from accuracy studies using synthetic experiments and a range of experimental applications to turbulent flows in small and large scale volumes (up to cubic-meter-scales using HFSB seeding). The combined availability of a large number of samples of dense 3D Lagrangian particle tracks and the full velocity gradient tensor allows for a multitude of evaluation options, e.g.:
    • extracting instantaneous 3D pressure fields and determining related loads on surfaces
    • investigating the spatial and temporal development of coherent flow structures
    • computing mean profiles (velocity, Reynolds stresses, acceleration) in sub-pixel resolution
    • computing other one- and two-point–statistics (e.g. Joint PDFs, two-point-correlations, dissipation rate) in an adaptive (and conditional) bin-averaging approach
    • determining conditional analysis and statistics of flow events in a combined Lagrangian and Eulerian frame
    Examples of the listed approaches for flow analyses and turbulence characterization based on experimental data will be discussed.
  14. 14. Prof. Jin-Jun Wang(Beijing University of Aeronautics and Astronautics, China)

    Title
    A new kind of bypass transition: experimental exploration on the laminar bounday layer transition induced by vortex
    Abstract
    A bypass transition scenario induced by cylinder wake vortex is first explored experimrntally, which is totally different from the Klebanoff mode induced by high freestream turbulence. This transition scenario is mainly characterized as: (i) generation of secondary transverse vortical structures near the flat plate surface in response to the von Karman vortex street of the cylinder; (ii) formation of hairpin vortices due to the secondary instability of secondary vortical structures; (iii) growth of hairpins which is accelerated by wake-vortex induction; (iv) formation of hairpin packets and the associated streaky structures. Moreover, the effect of cylinder diameter, location are considered, and the mechanism of disturbance receptivity and evolution are discussed in detail. It is revealed that when the cylinder is close enough to the wall (G/D=2.0), the cylinder wake vortices can periodically induce secondary spanwise vortices in the boundary layer. As the cylinder approaches the wall (G/D = 1.0) the secondary vortex directly interacts with the lower wake vortex, and a further approaching of the cylinder (G/D = 0.5) can results in more complex interactions with the added involvement of the upper wake vortex. For G/D < 0.25, the lower shear layer is strongly inhibited and only upper shear layer can shed vortices.
  15. 15. Prof. Steven Wereley(Purdue University, USA)

    Title
    Particle Diffusometry
    Abstract
    Miniaturized platforms for analyzing biopharmaceutical degradation provide significant advantages to current macroscale systems. Primary among these is the reduction of sample size of potentially expensive pharmaceuticals. Since there is no existing method to rapidly study biopharmaceutical expiration in the production facility or once the biopharmaceutical leaves the production facility, this opens up a new research realm to develop a method to screen for the degradation of biopharmaceuticals. We call our approach particle diffusometry (PD). It is a direct descendent of particle diffusometry ideas developed over the last 15 years(Clayton, Salameh, Wereley, & Kinzer-Ursem, 2016; Gorti, Shang, Wereley, & Lee, 2008; Hohreiter, Wereley, Olsen, & Chung, 2002). We use a simple microfluidic chip, fabricated by any several low-cost approaches (2-sided tape and microscope slides are the lowest cost version) into which we introduce sub-micron particles to a quiescent solution and calculate Brownian motion statistics of the particles via the characteristics of the cross-correlation peak. Through the Stokes-Einstein diffusion coefficient, we can detect two distinct phenomena: the effective hydrodynamic diameter of the particle increasing due to surface adhesion as well as viscosity increase due to rheology changes of the suspension. Depending on the pharmaceutical being tested, one or the other of these modalities (sometimes both) changes the particle diffusion. As an example we consider the degradation of insulin, a commonly used protein for patients with diabetes. We can discriminate intact insulin from degraded samples as a function of the solution viscosity. Another example is the functionalization of particles against certain proteins such as Calmodulin, Bovine Serum Albumin and Lysozyme. When the particles are properly functionalized and exposed to these proteins, they will acquire a surface layer of proteins which changes their effective hydrodynamic diameter and hence their diffusion speed. This is an effective way of detecting the presence of a certain protein in a sample.