Bulletin of the American Physical Society
68th Annual Meeting of the APS Division of Fluid Dynamics
Volume 60, Number 21
Sunday–Tuesday, November 22–24, 2015; Boston, Massachusetts
Session L33: Experiments: PIV Techniques |
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Chair: Jiarong Hong, University of Minnesota Room: Ballroom A |
Monday, November 23, 2015 4:05PM - 4:18PM |
L33.00001: Improvements on Digital Inline Holographic PIV for Turbulent Flow Measurement Jiarong Hong, Mostafa Toloui, Kevin Mallery Among all the 3D PIV techniques used in wall-bounded turbulent flow measurements, digital inline holographic (DIH) PIV provides the highest spatial resolution for near-wall flow diagnostics with low-cost, simple and compact optical set-ups. Despite these advantages, DIH-PIV suffers from major limitations including poor longitudinal resolution, human intervention (i.e. requirement for manually determined tuning parameters during tracer field reconstruction and extraction), limited tracer concentration, and expensive computations. These limitations prevent this technique from being widely implemented for high resolution 3D flow measurements. In this study, we present our work on improving holographic particle extraction algorithm with the goal of overcoming some of abovementioned limitations. Our new DIH-PIV processing method has been successfully implemented on multiple experimental cases ranging from 3D flow measurement within a micro-channel to imaging near-wall coherent structures in smooth and rough wall turbulent channel flows. [Preview Abstract] |
Monday, November 23, 2015 4:18PM - 4:31PM |
L33.00002: Volumetric Echocardiographic Particle Image Velocimetry (V-Echo-PIV) Ahmad Falahatpisheh, Arash Kheradvar Measurement of 3D flow field inside the cardiac chambers has proven to be a challenging task. Current laser-based 3D PIV methods estimate the third component of the velocity rather than directly measuring it and also cannot be used to image the opaque heart chambers. Modern echocardiography systems are equipped with 3D probes that enable imaging the entire 3D opaque field. However, this feature has not yet been employed for 3D vector characterization of blood flow. For the first time, we introduce a method that generates velocity vector field in 4D based on volumetric echocardiographic images. By assuming the conservation of brightness in 3D, blood speckles are tracked. A hierarchical 3D PIV method is used to account for large particle displacement. The discretized brightness transport equation is solved in a least square sense in interrogation windows of size $16^3$ voxels. We successfully validate the method in analytical and experimental cases. Volumetric echo data of a left ventricle is then processed in the systolic phase. The expected velocity fields were successfully predicted by V-Echo-PIV. In this work, we showed a method to image blood flow in 3D based on volumetric images of human heart using no contrast agent. [Preview Abstract] |
Monday, November 23, 2015 4:31PM - 4:44PM |
L33.00003: Effect of random errors in planar PIV data on pressure estimation in vortex dominated flows. Jeffrey McClure, Serhiy Yarusevych The sensitivity of pressure estimation techniques from Particle Image Velocimetry (PIV) measurements to random errors in measured velocity data is investigated using the flow over a circular cylinder as a test case. Direct numerical simulations are performed for Re$_{\mathrm{D}}=$ 100, 300 and 1575, spanning laminar, transitional, and turbulent wake regimes, respectively. A range of random errors typical for PIV measurements is applied to synthetic PIV data extracted from numerical results. A parametric study is then performed using a number of common pressure estimation techniques. Optimal temporal and spatial resolutions are derived based on the sensitivity of the estimated pressure fields to the simulated random error in velocity measurements, and the results are compared to an optimization model derived from error propagation theory. It is shown that the reductions in spatial and temporal scales at higher Reynolds numbers leads to notable changes in the optimal pressure evaluation parameters. The effect of smaller scale wake structures is also quantified. The errors in the estimated pressure fields are shown to depend significantly on the pressure estimation technique employed. The results are used to provide recommendations for the use of pressure and force estimation techniques from experimental PIV measurements in vortex dominated laminar and turbulent wake flows. [Preview Abstract] |
Monday, November 23, 2015 4:44PM - 4:57PM |
L33.00004: Volumetric Real-time Wide Field Microscopy with Tunable Acoustic Lens: A New Tool for MicroPIV Ting Hsuan Chen, Craig Arnold Obtaining volumetric images with high frame rate is a fundamental challenge for 3D micro Particle Image Velocimetry (PIV) used in characterizing the dynamics of fluid systems. In this presentation, we propose a new method based on a tunable acoustic lens integrated in a simple optical system. By synchronizing a pulsed LED with a high-speed camera, we are able to resolve a volume of 2 mmm by 2mm with depth 1mm in 7 us. The ability to resolve a volume of fluid in microseconds opens the door to exploring the fundamental dynamics in small-scale fluid systems. [Preview Abstract] |
Monday, November 23, 2015 4:57PM - 5:10PM |
L33.00005: Characterization of Flow Bench Engine Testing Alex Voris, Lauren Riley, Paul Puzinauskas This project was an attempt at characterizing particle image velocimetry (PIV) and swirl-meter test procedures. The flow direction and PIV seeding were evaluated for in-cylinder steady state flow of a spark ignition engine. For PIV seeding, both wet and dry options were tested. The dry particles tested were baby powder, glass particulate, and titanium dioxide. The wet particles tested were fogs created with olive oil, vegetable oil, DEHS, and silicon oil. The seeding was evaluated at 0.1 and 0.25 Lift/Diameter and at cylinder pressures of 10, 25 and 40 inches of H$_{2}$O. PIV results were evaluated through visual and fluid momentum comparisons. Seeding particles were also evaluated based on particle size and cost. It was found that baby powder and glass particulate were the most effective seeding options for the current setup. The oil fogs and titanium dioxide were found to deposit very quickly on the mock cylinder and obscure the motion of the particles. Based on initial calculations and flow measurements, the flow direction should have a negligible impact on PIV and swirl-meter results. The characterizations found in this project will be used in future engine research examining the effects of intake port geometry on in-cylinder fluid motion and exhaust gas recirculation tolerances. [Preview Abstract] |
Monday, November 23, 2015 5:10PM - 5:23PM |
L33.00006: Instantaneous, phase-averaged, and time-averaged pressure from particle image velocimetry Roeland de Kat Recent work on pressure determination using velocity data from particle image velocimetry (PIV) resulted in approaches that allow for instantaneous and volumetric pressure determination. However, applying these approaches is not always feasible (e.g.~due to resolution, access, or other constraints) or desired. In those cases pressure determination approaches using phase-averaged or time-averaged velocity provide an alternative. To assess the performance of these different pressure determination approaches against one another, they are applied to a single data set and their results are compared with each other and with surface pressure measurements. For this assessment, the data set of a flow around a square cylinder (de Kat \& van Oudheusden, 2012, \emph{Exp. Fluids} 52:1089--1106) is used. [Preview Abstract] |
Monday, November 23, 2015 5:23PM - 5:36PM |
L33.00007: Error propagation in PIV-based Poisson pressure calculations Zhao Pan, Jared Whitehead, Scott Thomson, Tadd Truscott After more than 20 years of development, PIV has become a standard non-invasive velocity field measurement technique, and promises to make PIV-based pressure calculations possible. However, the errors inherent in PIV velocity fields propagate through integration and contaminate the calculated pressure field. We propose an analysis that shows how the uncertainties in the velocity field propagate to the pressure field through the Poisson equation. First we model the dynamics of error propagation using boundary value problems (BVPs). Next, L$_{2}$-norm and/or L$_{\infty}$-norm are utilized as the measure of error in the velocity and pressure field. Finally, using analysis techniques including the maximum principle, the Poincare inequality pressure field can be bounded by the error level of the data by considering the well-posedness of the BVPs. Specifically, we exam if and how the error in the pressure field depend continually on the BVP data. Factors such as flow field geometry, boundary conditions, and velocity field noise levels will be discussed analytically. [Preview Abstract] |
Monday, November 23, 2015 5:36PM - 5:49PM |
L33.00008: PIV-based estimation of unsteady loads on a flat plate at high angle of attack using momentum equation approaches Amandine Guissart, Luis Bernal, Gregorios Dimitriadis, Vincent Terrapon The direct measurement of loads with force balance can become challenging when the forces are small or when the body is moving. An alternative is the use of Particle Image Velocimetry (PIV) velocity fields to indirectly obtain the aerodynamic coefficients. This can be done by the use of control volume approaches which lead to the integration of velocities, and other fields deriving from them, on a contour surrounding the studied body and its supporting surface. This work exposes and discusses results obtained with two different methods: the direct use of the integral formulation of the Navier-Stokes equations and the so-called Noca's method. The latter is a reformulation of the integral Navier-Stokes equations in order to get rid of the pressure. Results obtained using the two methods are compared and the influence of different parameters is discussed. The methods are applied to PIV data obtained from water channel testing for the flow around a 16:1 plate. Two cases are considered: a static plate at high angle of attack and a large amplitude imposed pitching motion. Two-dimensional PIV velocity fields are used to compute the aerodynamic forces. Direct measurements of dynamic loads are also carried out in order to assess the quality of the indirectly calculated coefficients. [Preview Abstract] |
Monday, November 23, 2015 5:49PM - 6:02PM |
L33.00009: Combined PIV, PLIF, and laser focal displacement measurements (LFDM) to quantify gas-liquid interfacial shear stress Ian McCarthy, David Hann, Buddhika Hewakandamby, Barry Azzopardi Simultaneous Particle image velocimetry (PIV) and Planar Laser Induced Fluorescence imaging (PLIF), using a pulsed Nd:YAG laser alongside a specially design optical system to produce a pair of very fine light sheets. This equipment, coupled a dual set of high speed synchronized camera, and a combination of reflective seeding particles, fluorescent dye and tracers were used to calculate the shear stress at the gas –liquid interface by determining the velocity vectors in both phases. These quantities, along with the position and profile of the interface were found at a number of different inlet conditions. These conditions related to various flow pattern regimes commonly discussed within the literature. These regimes; stratified, stratified- wavy, 2-D and 3-D waves are seen at various liquid and gas Reynolds values, with increasing complexity occurring as higher Reynolds numbers. Validation of the results was done via computing the shear stress in a number of different ways, and also compared with result of temporal film thickness taken using the LFDM. Results from these tests show good agreement with one another and those found in literature, with determination of gas-liquid shear stress found for regimes not previously investigated in this manner. [Preview Abstract] |
Monday, November 23, 2015 6:02PM - 6:15PM |
L33.00010: DeepPIV: Particle image velocimetry measurements using deep-sea, remotely operated vehicles Kakani Katija, Alana Sherman, Dale Graves, Denis Klimov, Chad Kecy, Bruce Robison The midwater region of the ocean (below the euphotic zone and above the benthos) is one of the largest ecosystems on our planet, yet remains one of the least explored. Little-known marine organisms that inhabit midwater have developed life strategies that contribute to their evolutionary success, and may inspire engineering solutions for societally relevant challenges. Although significant advances in underwater vehicle technologies have improved access to midwater, small-scale, in situ fluid mechanics measurement methods that seek to quantify the interactions that midwater organisms have with their physical environment are lacking. Here we present DeepPIV, an instrumentation package affixed to remotely operated vehicles that quantifies fluid motions from the surface of the ocean down to 4000 m depths. Utilizing ambient suspended particulate, fluid-structure interactions are evaluated on a range of marine organisms in midwater. Initial science targets include larvaceans, biological equivalents of flapping flexible foils, that create mucus houses to filter food. Little is known about the structure of these mucus houses and the function they play in selectively filtering particles, and these dynamics can serve as particle-mucus models for human health. Using DeepPIV, we reveal the complex structures and flows generated within larvacean mucus houses, and elucidate how these structures function. [Preview Abstract] |
(Author Not Attending)
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L33.00011: A method to resolve low velocities in a PIV system Sunil Bharadwaj, Meheboob Alam A method is proposed to improve the velocity-dynamic range (VDR) of particle-image velocimetry (PIV) technique. This method uses two different timings of a pulsed laser and an outlier detection technique that helped to measure very low velocities, bypassing the limits set by the VDR of the PIV-system. The lower limit of the resolvable velocity is not set by the algorithm but by the laser-timings. The reliability of the method is verified by carrying our planar measurements of the mean and fluctuation velocities in an axisymmetric jet at a Reynolds number of about 3500. The radial velocity, which is usually an order-of-magnitude lower than the axial velocity, is successfully resolved in the ambient region of the jet as compared to results obtained by employing the post-processing techniques of the standard PIV-system. Overall, the proposed method seems to increase the velocity-dynamic range of PIV-algorithm to capture low-velocities in an otherwise fast flow. [Preview Abstract] |
Monday, November 23, 2015 6:28PM - 6:41PM |
L33.00012: Image-processing method for near-wall PIV measurement around a moving interface Lichao Jia, Yiding Zhu, Huijing Yuan, Cunbiao Lee This paper presents a PIV (particle image velocimetry) image processing method for the near-wall measurement when the interface is moving. Based on the successful interface tracking and precise determination of the velocity of the interface, the optimal synthetic particles with the kinetic information of the interface are added into the original particle image. The performance of the velocity estimation near the wall is then improved by the effective restriction of the particles from both sides of the interface. Quantitative evaluations of this method have been performed by applying it to Monte Carlo simulations and experimental tests. The improved method could help to provide more reliable results for the measurement of the flows around a rotating blade. [Preview Abstract] |
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