Three-dimensional Particle Image Velocimetry Research Articles

ENGINEERING IMAGING: USING PARTICLE IMAGE VELOCIMETRY TO SEE PHYSIOLOGY IN A NEW LIGHT

1. Despite the array of sophisticated imaging techniques available for biological applications, none of the standard biomedical techniques adequately provides the capability to measure motion and flow. Those techniques currently in use are particularly lacking in spatial and temporal resolution. 2. Herein, we introduce the technique of particle image velocimetry. This technique is a well-established tool in engineering research and industry. Particle image velocimetry is continuing to develop and has an increasing number of variants. 3. Three case studies are presented: (i) the use of microparticle image velocimetry to study flow generated by high-frequency oscillatory ventilation in a human airway model; (ii) the use of stereoparticle image velocimetry to study stirred cell and tissue culture devices; and (iii) a three-dimensional X-ray particle image velocimetry technique used to measure flow in an in vitro vascular flow model. 4. The case studies highlight the vast potential of applying the engineering technique of particle image velocimetry and its many variants to current research problems in physiology.

The study for particle image velocimetry system based on binocular vision

In this paper, a new matching model is integrated into standard techniques of three-dimensional (3D) particle image velocimetry (PIV) based on the binocular vision. A 3D space is first segmented and aligned to 2D planes. Then the 2D PIV method or the particle tracking velocimetry (PTV) method is applied to match particles within different interrogation windows. Using the proposed algorithm, problems on spatial stereo matching and information representation can be solved. At last, the algorithm is applied to the real and synthetic particle images, and the results are analyzed. These experiments demonstrate that the proposed approach is effective and practical.

Measurement of turbulent flow phenomena for the lower plenum of a prismatic gas-cooled reactor

Mean velocity field and turbulence data are presented that measure turbulent flow phenomena in an approximately 1:7 scale model of a region of the lower plenum of a typical prismatic gas-cooled reactor (GCR) similar to a General Atomics design (Gas-Turbine-Modular Helium Reactor). The data were obtained in the Matched-Index-of-Refraction (MIR) facility at Idaho National Laboratory (INL) and are offered as a benchmark for assessing computational fluid dynamics (CFD) software. This experiment has been selected as the first Standard Problem endorsed by the Generation IV International Forum. The primary objective of this paper is to document the experiment and present a sample of the data set that has been established for this standard problem. Present results concentrate on the region of the lower plenum near its far reflector wall (away from the outlet duct). The flow in the lower plenum consists of multiple jets injected into a confined crossflow—with obstructions. The model consists of a row of full circular posts along its centerline with half-posts on the two parallel walls to approximate flow scaled to that expected from the staggered parallel rows of posts in the reactor design. Posts, side walls and end walls are fabricated from clear, fused quartz to match the refractive index of the mineral oil working fluid so that optical techniques may be employed for the measurements. The benefit of the MIR technique is that it permits optical measurements to determine flow characteristics in complex passages and around objects to be obtained without locating intrusive transducers that will disturb the flow field and without distortion of the optical paths. An advantage of the INL system is its large size, leading to improved spatial and temporal resolution compared to similar facilities at smaller scales. A three-dimensional (3D) particle image velocimetry (PIV) system was used to collect the data. Inlet-jet Reynolds numbers (based on the hydraulic diameter of the jet and the time-mean average flow rate) are approximately 4300 and 12,400. Uncertainty analysis and a discussion of the standard problem are included. The measurements reveal complicated flow patterns that include several large recirculation zones, reverse flow near the simulated reflector wall, recirculation zones in the upper portion of the plenum and complex flow patterns around the support posts. Data include three-dimensional PIV images of flow planes, data displays along the coordinate planes (slices) and presentations that describe the component flows at specific regions in the model.

Three-dimensional synchrotron x-ray particle image velocimetry

There is great potential to vastly improve biological flow measurement by using a combination of synchrotron imaging and the latest experimental flow measurement techniques. In the current paper, the three-dimensional velocity field within a cylindrical tube is measured using a combination of phase-contrast x-ray imaging and particle image velocimetry (PIV). We greatly refine the techniques previously used to undertake velocity measurements with a synchrotron light source, substantially enhancing accuracy. Furthermore a PIV correlation peak analysis is developed to allow three-dimensional measurement of the velocity field.

EHD flow measured by 3D PIV in a narrow electrostatic precipitator with longitudinal-to-flow wire electrode and smooth or flocking grounded plane electrode

In this work, results of three-dimensional (3D) Particle Image Velocimetry (PIV) measurements of the electrohydrodynamic (EHD) flow velocity fields in a narrow electrostatic precipitator (ESP) with a longitudinal-to-flow placed wire electrode are presented. The ESP was a narrow transparent acrylic box (90 mm×30 mm×30 mm). The electrode set consisted of a single wire discharge electrode and two plane collecting electrodes. Either two smooth stainless-steel plates or two stainless-steel plane meshes with nylon flocks were used as the collecting electrodes. The 3D PIV measurements were carried out in two parallel planes, placed longitudinally to the flow duct. The positive DC voltage of up to 9.5 kV was applied to the wire electrode through a 10 MΩ resistor. The collecting electrodes were grounded. The measurements were carried out at a primary flow velocity of 0.5 m/s. Obtained results show that the flow patterns for the smooth-plate electrodes and for the flocking plane electrodes are similar in the bulk of the flow. However, the flow velocities near the flocking plane electrodes are much lower than those near the smooth-plate electrodes. This is a beneficial phenomenon, because the lower the flow near the collecting electrodes, the lower re-entrainment of the particles deposited on the collecting electrodes occurs.

An investigation of the flow characteristics in the bootdeck region of a scale model notchback saloon vehicle

The results of an experimental investigation of the bootdeck flow structure of a 36 per cent scale model notchback car are presented together with a general review of advanced laser diagnostic techniques suitable for large-scale wind tunnel flow measurement. The tests were used to characterize the flow behaviour over the Reynolds number range 0.74 × 106-4.93 × 106 in the Cranfield University 2.4 m × 1.8 m wind tunnel. The experiments involved flow visualization, rear bootdeck and backlight three-dimensional stereoscopic particle image velocimetry (PIV) measurements, and mean static and unsteady static pressure measurements. Initial results from the flow visualization suggested flow asymmetries originating in the backlight region that were sensitive to the Reynolds number. The PIV data and static pressure data, however, showed little or no sensitivity of flow to Reynolds number with consistent flow structure and levels of unsteadiness from the backlight to the rear bootdeck region. At this stage no definitive reasons can be given for the discrepancies between the flow visualization and the other data, although the flow visualization data were particularly difficult to interpret near the backlight, and the near-wake structure may be bi-stable in this Reynolds number range. More detailed three-dimensional stereoscopic, time-resolved PIV flow data are now planned to quantify conclusively the correct flow structure and its sensitivities.

Spatial resolution enhancement/smoothing of stereo–particle-image-velocimetry data using proper-orthogonal-decomposition–based and Kriging interpolation methods

Methods for data reconstruction and spatial enhancement of experimental data for a transitional boundary layer with laminar separation bubble are investigated. Particularly, proper orthogonal decomposition (POD) is applied to direct numerical simulation (DNS) data to extract the DNS-based POD modes, which are projected onto the experimental data (via a least-squares procedure) in order to obtain model coefficients. These model coefficients are then used to reconstruct, “interpolate,” and smooth the experimental data based on the DNS modes. In addition, in order to compare and assess the effectiveness of the present DNS-based procedure, Kriging interpolation is performed on the experimental (as well as numerical) data. These procedures are applied to time periodic (experimental) instantaneous spanwise vorticity (ωz) at a constant spanwise location. We have demonstrated that particle-image-velocimetry (PIV)-based POD modes can be smoothed by Kriging interpolation, thus a noise-free reconstruction of PIV data can be achieved. It is also found that for very low resolution experimental data, DNS-based interpolation is superior over Kriging interpolation. On the other hand, Kriging interpolation based on the Gaussian correlation model works very well for sufficiently high resolution experimental data. The correlation parameter can be used to control the degree of smoothness in the data reconstruction. Both procedures effectively eliminate the unwanted noise in the experimental data. One important difference between the two procedures is that, with quite some confidence, the DNS-based procedure can also be used for “extrapolation” since the model coefficients do not depend on spatial variation. In fact, we show that near-wall spanwise vorticity, which is not available from experimental data, can be recovered faithfully. Moreover, the enhancement (interpolation and smoothing) of full three-dimensional PIV data has been performed by Kriging interpolation employing a Gaussian correlation model.

Study of axial velocity in gas cyclones by 2D-PIV, 3D-PIV, and simulation

The axial velocity distribution in a gas cyclone has been examined with two-dimensional particle image velocimetry (2D-PIV) and three-dimensional particle image velocimetry (3D-PIV) experiments in this study. Due to the limitation of 2D-PIV configuration, the contamination generated by the strong tangential velocity in the cyclone can be registered in the axial velocity detected by 2D-PIV. Efficient methods are proposed in this work to remove this contamination. The contamination-removed 2D-PIV data agree well with 3D-PIV results. The distributions of the axial velocity are also computed by the Reynolds stress model (RSM) and verified using the PIV experimental results. Reasonable agreements are obtained.

Fluid Dynamic Assessment of Three Polymeric Heart Valves Using Particle Image Velocimetry

Polymeric heart valves have the potential to reduce thrombogenic complications associated with current mechanical valves and overcome fatigue-related problems experienced by bioprosthetic valves. In this paper we characterize the in vitro velocity and Reynolds Shear Stress (RSS) fields inside and downstream of three different prototype trileaflet polymeric heart valves. The fluid dynamic differences are then correlated with variations in valve design parameters. The three valves differ in leaflet thickness, ranging from 80 to 120 mum, and commisural design, either closed, opened, or semi-opened. The valves were subjected to aortic flow conditions and the velocity measured using three-dimensional stereo Particle Image Velocimetry. The peak forward flow phase in the three valves was characterized by a strong central orifice jet of approximately 2 m/s with a flat profile along the trailing edge of the leaflets. Leakage jets, with principle RSS magnitudes exceeding 4,500 dyn/cm(2), were observed in all valves with larger leaflet thicknesses and also corresponded to larger leakage volumes. Additional leakage jets were observed at the commissural region of valves with the open and the semi-open commissural designs. The results of the present study indicate that commissural design and leaflet thickness influence valve fluid dynamics and thus the thrombogenic potential of trileaflet polymeric valves.

Application of three-dimensional hybrid stereoscopic particle image velocimetry to breaking waves

A new technique of three-dimensional hybrid stereoscopic particle image velocimetry (3D hybrid SPIV) for measuring a volumetric spatial distribution of three-dimensional velocity is presented in this paper. The accuracy and uncertainty of this technique are examined by numerical tests. The 3D hybrid SPIV has been found to be able to measure major features of velocity field involving a vortex with turbulence in a shear flow. This technique is used for measuring an instantaneous three-dimensional flow structure under breaking waves. The formation of the three-dimensional vortex structures involving roller and longitudinal vortices in breaking waves is investigated in this study.

A fluid dynamics approach to bioreactor design for cell and tissue culture

The problem of controlling cylindrical tank bioreactor conditions for cell and tissue culture purposes has been considered from a flow dynamics perspective. Simple laminar flows in the vortex breakdown region are proposed as being a suitable alternative to turbulent spinner flask flows and horizontally oriented rotational flows. Vortex breakdown flows have been measured using three-dimensional Stereoscopic particle image velocimetry, and non-dimensionalized velocity and stress distributions are presented. Regions of locally high principal stress occur in the vicinity of the impeller and the lower sidewall. Topological changes in the vortex breakdown region caused by an increase in Reynolds number are reflected in a redistribution of the peak stress regions. The inclusion of submerged scaffold models adds complexity to the flow, although vortex breakdown may still occur. Relatively large stresses occur along the edge of disks jutting into the boundary of the vortex breakdown region.

EHD flow in a wide electrode spacing spike–plate electrostatic precipitator under positive polarity

In this work, results of two- and three-dimensional particle image velocimetry (PIV) measurements of the flow velocity fields in a wide spacing spike–plate electrostatic precipitator (ESP) under positive polarity are presented. A DC voltage of positive polarity (up to 28 kV) was applied to the spike electrode. The average gas flow velocity was 0.6 m/s. The PIV measurements were carried out in four planes perpendicular to the plate electrodes. Three parallel planes passed along the ESP while one plane passed across the ESP duct. The results show that electrohydrodynamic (EHD) secondary flow with relatively strong vortices exist in the ESP. The EHD secondary flow pattern depends on applied voltage and measuring plane position in respect to the spike tip. The strongest vortices occur in the plane passing through the tip of the upstream-directed spike. These relatively strong EHD vortices may hinder collection of the particles in the diameter range of 0.1–1 μm in the wide electrode spacing spike–plate ESPs.

An experimental study of three-dimensional vortical structures between co-rotating disks

In this study, we experimentally investigate the flow between co-rotating disks in a stationary cylindrical enclosure. Here, the gap between disks is much narrower than disk radius. This flow is often non-axisymmetrical and complicated. This flow sometimes induces magnetic-head oscillations in disk storage devices of PCs. We carry out flow visualisations using a high-speed camera, and time-successive three-dimensional PIV (Particle Image Velocimetry) analyses of visualised pictures. We focus on the relation and combination of axial modes with circumferencial modes. Tested cases are two, that is, A (Re = 1.2 × 104 and δ = 0.12) and B (Re = 1.0 × 105 and δ = 0.20). Here, Re is the rotating Reynolds number, and δ is a non-dimensional gap. Case A is in axial mode II and circumferencial mode 8-9, and case B is in axial mode III and circumferencial mode 4. Axial modes are related with the symmetry of a pair of toroidal-vortical structures and circumferencial modes are related with the radial fluctuation of these structures as well as the solid-body-rotation core. As a result, in case A, the vortical structures are mainly influenced by axial mode (II) in the z direction, but not influenced by both axial mode (II) and circumferencial mode (8-9) in the r direction. In case B, the vortical structures are mainly influenced by axial mode (III), but influenced by circumferencial mode (4) in the r direction.

Robust genetic algorithm for high-accuracy particle position estimation in three-dimensional particle image velocimetry applications

A method for three-dimensional particle position estimation employed in particle image velocimetry applications is presented. The method includes the application of a robust optimization process, which involves the use of a genetic algorithm. The algorithm derives particle position by pattern matching theoretical to experimental images, using the concept of image peak signal-to-noise ratio as the objective error measure for this comparison. To produce sufficiently accurate theoretical images comparable to experimental images for positioning purposes, it is found that a Lorenz-Mie treatment of the seeding scattering field was required, which also took into consideration the incident wavefront. The use of a genetic algorithm for positioning proved to be more accurate and faster than a Nelder-Mead algorithm combined with neural nets used previously. This method has also been shown to be an effective means of isolating contaminant particles in velocimetry images, which can sub- stantially increase the overall error. We discuss some aspects of the theory regarding this method, illustrate the ideas with a simple experi- mental image, as well as detail our implementation of a pattern-matching approach combined with a genetic algorithm for positioning purposes. © 2003 Society of Photo-Optical Instrumentation Engineers. (DOI: 10.1117/1.1533038) Subject terms: diffraction pattern; genetic algorithms; particle position estimation; tunneling velocimetry; particle image velocimetry.

The development of a three—dimensional imaging system and its application in fluid mechanics

This paper details the application of a three-dimensional imaging system known as planar contour imaging (PCI) to the presentation of experimental fluid mechanics data. The experimental datasets consisted of pseudo three-dimensional particle image velocimetry (PIV) vector maps of the flowfield around an air bubble growing at the base of a water column. The vectors from the experimental datasets were projected into three-dimensional space and the ease of their interpretation was assessed. It was found that the selection of the correct type and amount of data presented to the viewer was critical. However, when the image was refined, the three-dimensional image was found to produce an impressive representation of the flowfield contained within the experimental dataset.

Two-axes Scheimpflugfocusing for particle image velocimetry

The objective of this work is to demonstrate the capabilities ofa two-axes, three-dimensional particle image velocimetry (PIV)system for future use as a large-scale wind tunnel researchtool. A two-axes PIV system provides the capability for cameraplacement virtually anywhere within three-dimensional spacerelative to the laser sheet plane of measurement. TheScheimpflug focusing method is applied in two orthogonal axesto achieve off-axis focusing. The two-axes, three-dimensionalPIV system uses off-axis stereoscopic viewing to determine twoperspective measurements of a three-dimensional velocity fieldwithin the laser sheet. A unique calibration procedure is usedto determine the optical parameters that describe the positionof the camera systems and which are necessary to perform thethree-dimensional reconstruction of the displacements. This paper presents the calibration procedure as well as a method forreconstructing the three-dimensional particle displacements forthis two-axes, three-dimensional PIV system. This two-axes,three-dimensional PIV system was demonstrated by measuringthree-dimensional displacements of a target. Maximuminstantaneous errors are estimated as 2% or less for all velocity components. These error estimates are for instantaneousdisplacements and include all error sources. The two-axes,three-dimensional PIV system was also used to make measurementsof the freestream velocity within a wind tunnel. Theout-of-plane freestream component of velocity measured by thePIV system differed from the expected value by less than 1.1{%}.

THE MEASUREMENT OF THE FLOW AROUND A SPHERE SETTLING IN A RECTANGULAR BOX USING 3-DIMENSIONAL PARTICLE IMAGE VELOCIMETRY

A novel three-dimensional particle image velocimetry technique is used to measure the planar three-dimensional flow field about the centreline of a sphere sedimenting in a rectangular shaped box. Measurements are made in the center of the container and also one diameter from a plane wall. Results are presented for a sphere falling in both a constant viscosity elastic (Boger) fluid and a shear-thinning elastic liquid. In the center of the box, the flow field is essentially two-dimensional as expected. Near the wall, there is substantial out-of-plane motion in the shear-thinning solution due to the presence of the wall. Surprisingly, there is little out-of-plane motion for a sphere sedimenting near the wall in the Boger fluid. There are significant qualitative differences in the flow field for the sphere sedimenting in the shear-thinning and constant viscosity elastic liquids. The results are compared with previously published work for a sphere settling in a non-Newtonian fluid and also with results obtained in an identical geometry for a Newtonian fluid. Reasons for the differences in the velocity maps are discussed. The drag coefficient for each geometry and fluid is calculated.

Functional morphology of the pectoral fins in bamboo sharks, Chiloscyllium plagiosum: benthic vs. pelagic station-holding.

Bamboo sharks (Chiloscyllium plagiosum) are primarily benthic and use their relatively flexible pectoral and pelvic fins to rest on and move about the substrate. We examined the morphology of the pectoral fins and investigated their locomotory function to determine if pectoral fin function during both benthic station-holding and pelagic swimming differs from fin function described previously in leopard sharks, Triakis semifasciata. We used three-dimensional kinematics and digital particle image velocimetry (DPIV) to quantify pectoral fin function in five white-spotted bamboo sharks, C. plagiosum, during four behaviors: holding station on the substrate, steady horizontal swimming, and rising and sinking during swimming. During benthic station-holding in current flow, bamboo sharks decrease body angle and adjust pectoral fin angle to shed a clockwise fluid vortex. This vortex generates negative lift more than eight times that produced during open water vertical maneuvering and also results in an upstream flow that pushes against the posterior surface of the pectoral fin to oppose drag. In contrast, there is no evidence of significant lift force in the wake of the pectoral fin during steady horizontal swimming. The pectoral fin is held concave downward and at a negative dihedral angle during steady horizontal swimming, promoting maneuverability rather than stability, although this negative dihedral angle is much less than that observed previously in sturgeon and leopard sharks. During sinking, the pectoral fins are held concave upward and shed a clockwise vortex with a negative lift force, while in rising the pectoral fin is held concave downward and sheds a counterclockwise vortex with a positive lift force. Bamboo sharks appear to sacrifice maneuverability for stability when locomoting in the water column and use their relatively flexible fins to generate strong negative lift forces when holding position on the substrate and to enhance stability when swimming in the water column.

32ニューラルネットワークによる3次元速度場の推定

PIV (Particle Image Velocimetry) is widely applied to analyze complex flows. The velocity fields obtained by PIV, however, contain some unmeasurable areas. In particular, three-dimensional PTV provides sparsely distributed velocity vectors in principle. It has been required accordingly to develop the whole field estimation methods and we have proposed an estimation method using artificial neural networks for two-dimensional flows.This paper presents two new estimation methods for three-dimensional flows which is based on previously proposed one. The neural networks in the methods learn the whole field velocity distribution from PIV-measured one so that the estimated velocity vector fields agree with measured one in the original field and satisfy the continuity equation of flow. We additionally evaluate the proposed methods by applying them to the three-dimensional PIV standard images.

Three-dimensional particle image velocimetry: a low-cost 35 mm angular stereoscopic system for liquid flows

A low-cost 35 mm PIV stereoscopic system for liquid flows is presented which has an imaging component cost under US$9000. The system uses an angular configuration, rotating mirror image shifting and in-situ calibration techniques. Image processing algorithms based on cross correlation and bicubic interpolation are also used to calculate the 3D data from the PIV images. Results from an error analysis have shown the system to have in plane errors ranging from 4.15 to 5.95% and out of plane errors of 7.01% providing an f-number of f2 is fixed for all imaging. Subsequent application of the system to a flow field generated by a free falling sphere in wheat syrup have produced results which when compared to previous flow visualisation give good qualitative agreement. Suggested improvements to the PIV system costing US$1300 would allow operation at f-numbers down to f by modifying the cameras for the Scheimpflug condition and using a corrective liquid prism.