Quantitative flow analysis around aquatic animals using laser sheet particle image velocimetry

Two alternative particle image velocimetry (PIV) methods have been developed, applying laser light sheet illumination of particle-seeded flows around marine organisms. Successive video images, recorded perpendicular to a light sheet parallel to the main stream, were digitized and processed to map the flow velocity in two-dimensional planes. In particle tracking velocimetry (PTV), displacements of single particles in two subsequent images were determined semi-automatically, resulting in flow diagrams consisting of non-uniformly distributed velocity vectors. Application of grid-cell averaging resulted in flow field diagrams with uniform vector distribution. In sub-image correlation PIV (SCPIV), repetitive convolution filtering of small sub-areas of two subsequent images resulted in automatic determination of cross-correlation peaks, yielding flow field diagrams with regularly spaced velocity vectors. In both PTV and SCPIV, missing values, caused by incomplete particle displacement information in some areas of the images or due to rejection of some erroneous vectors by the vector validation procedure, were interpolated using a two-dimensional spline interpolation technique. The resultant vector flow fields were used to study the spatial distribution of velocity, spatial acceleration, vorticity, strain and shear. These flow fields could also be used to test for flow in the third dimension by studying the divergence, and to detect the presence and location of vortices. The results offer detailed quantitative descriptions of the flow morphology and can be used to assess dissipated energy. The versatile character of the technique makes it applicable to a wide range of fluid mechanical subjects within biological research. So far it has been successfully applied to map the flow around swimming copepods, fish larvae and juvenile fish and the ventilation current of a tube-living shrimp.

Download Full-text

Investigations of flow alteration of commissural misalignment of TAVR using Particle Image Velocimetry

Current Directions in Biomedical Engineering ◽

10.1515/cdbme-2020-3041 ◽

2020 ◽

Vol 6 (3) ◽

pp. 159-163

Author(s):

Finja Borowski ◽

Jan Oldenburg ◽

Sylvia Pfensig ◽

Sebastian Kaule ◽

Stefan Siewert ◽

...

Keyword(s):

Particle Image Velocimetry ◽

Flow Field ◽

Vector Fields ◽

Particle Image ◽

Clinical Performance ◽

Circulation Model ◽

Measuring Method ◽

Flow Fields ◽

Native Valve ◽

Image Velocimetry

AbstractDue to the raising number of TAVR implantations (transcatheter aortic valve replacement), tests for durability and prevention of associated diseases are becoming increasingly important. Not only the anatomy but also the positioning of the TAVR is decisive for its clinical performance. A misalignment in the circumferential direction can influence the flow in the sinus and thus inhibit the blood supply of the coronary arteries and influence the thrombosis potential. Therefore, the modification of the flow field is investigated in this study. For the characterization of the flow fields the measuring method of digital particle image velocimetry is used. A hydraulic circulation model is used to generate physiological flow and pressure conditions. Additionally, an aortic root model with Sinus Valsalvae, which represents the implantation environment, was developed. A prototype of a TAVR was implanted aligned to the commissure lines of the native valve leaflets on the one hand, and misaligned by 60 degree to the commissure of the native valves on the other hand. By determining the velocity vector fields, it could be shown that implantation of the TAVR with a commissureal misalignment influences the flow around the leaflets. A comparison of the flow fields shows that different recirculation areas occur. This is also indicated by a comparison of the mean velocities in the sinus and the observed shear rates. The influence of the altered flow field on the thrombosis and hemolysis potential should be investigated in future studies.

Download Full-text

Convergence of PIV Measurements at the Inlet of a Turbocharger Compressor

Volume 7: Fluids Engineering ◽

10.1115/imece2019-10461 ◽

2019 ◽

Author(s):

Deb Banerjee ◽

Ahmet Selamet ◽

Rick Dehner ◽

Keith Miazgowicz

Keyword(s):

Particle Image Velocimetry ◽

Flow Field ◽

Turbulent Flow ◽

Coefficient Of Variation ◽

Particle Image ◽

Flow Fields ◽

Statistical Moment ◽

Stereoscopic Particle Image Velocimetry ◽

Image Velocimetry ◽

The Mean

Abstract Particle Image Velocimetry has become a desirable tool to investigate turbulent flow fields in different engineering applications, including flames, combustion engines, and turbomachinery. The convergence characteristics of turbulent statistics of these flow fields are of prime importance since they help with the number of images (temporally uncorrelated) to be captured in order for the results to converge to a certain tolerance or with the assessment of the uncertainty of the measurements for a given number of images. The present work employs Stereoscopic Particle Image Velocimetry to examine the turbulent flow field at the inlet of an automotive turbocharger compressor without any recirculating channel. Optical measurements were conducted at five different mass flow rates spanning from choke to surge at a corrected rotational speed of 80 krpm. The velocity fields thus obtained were used to analyze the convergence of the mean (first statistical moment) and variance (second statistical moment) at different operating conditions. The convergence of the mean at a particular location in the flow field depends on the local coefficient of variation (COV). The number of required images for the mean to converge to a particular tolerance was also found to follow roughly a linear trend with respect to COV. While the convergence of the variance, on the other hand, did not appear to show any direct dependence on the coefficient of variation, it takes significantly more images than the mean to converge to the same level of tolerance.

Download Full-text

Assessing the interaction of air from a jet diffuser on a thermal plume in a room using two-dimensional particle image velocimetry

Building Services Engineering Research and Technology ◽

10.1177/0143624418824798 ◽

2019 ◽

Vol 40 (6) ◽

pp. 669-681 ◽

Cited By ~ 3

Author(s):

Yukun Xu ◽

Xin Wang ◽

Chen Huang ◽

Guangyao Du ◽

Yujie Zhang

Keyword(s):

Particle Image Velocimetry ◽

Flow Field ◽

Rational Design ◽

Particle Image ◽

Advanced Technology ◽

Thermal Plume ◽

Two Dimensional ◽

Airflow Distribution ◽

Image Velocimetry ◽

Velocity Attenuation

Traditional design of airflow distributions in large spaces does not consider the interference of thermal plumes on jets. In order to quantitatively describe the indoor environment, it is first necessary to quantify how the airflow gets distributed. In this study, a two-dimensional particle image velocimetry (PIV) system for measuring a wide indoor flow field was established. A total of 24 sub-regions (each with a size of 400 mm × 350 mm) were accurately measured in an unmanned room, and the overall cross-sectional flow field was obtained by splicing. Uncertainty analysis proved the rationality of this experimental method. According to the damage extent of the jet structure introduced by the thermal plume, two groups were divided, i.e. Groups A and B. The distribution of velocity fields, trajectories and velocity attenuation of jet centerlines, and velocity magnitude profiles at nozzle and head levels were compared and analyzed in detail. Through this investigation, detailed information of indoor air flow in large spaces can be effectively characterized, which can be useful to help understand the indoor physics and validate CFD models. Practical application: The key to creating a comfortable and healthy indoor thermal environment is the rational design of the airflow distribution. This paper proposes a method for quantitatively describing the airflow distribution in an enclosed space. The equation of the non-dimensional velocity attenuation of jet centerlines is obtained by using advanced technology (PIV), which provides theoretical basis and useful reference for the design of airflow distribution.

Download Full-text

Stereoscopic Particle Shadow Velocimetry

Volume 7: Fluids Engineering ◽

10.1115/imece2018-88013 ◽

2018 ◽

Author(s):

Jeff R. Harris ◽

Michael McPhail ◽

Christine Truong ◽

Arnold Fontaine

Keyword(s):

Particle Image Velocimetry ◽

Flow Field ◽

Particle Image ◽

Scattered Light ◽

Stereoscopic Particle Image Velocimetry ◽

Two Dimensional ◽

Tracer Particles ◽

Image Velocimetry ◽

Out Of Plane ◽

Led Backlight

Stereoscopic particle image velocimetry (SPIV) is a variant of particle image velocimetry (PIV) that allows for the measurement of three components of velocity along a plane in a flow field. In PIV, particles in the flow field are tracked by reflecting laser light from tracer particles into two angled cameras, allowing for the velocity field to be determined. Particle shadow velocimetry (PSV) is an inherently less expensive velocity measurement method since the method images shadows cast by particles from an LED backlight instead of scattered light from a laser. Previous studies have shown that PSV is an adequate substitute for PIV for many two-dimensional, two-component velocimetry measurements. In this work, the viability of the two-dimensional, three-component stereoscopic particle shadow velocimetry (SPSV) is demonstrated by using SPSV to examine a simple jet flow. Results obtained using SPIV are also used to provide benchmark comparison for SPSV measurements. Results show that in-plane and out-of-plane velocities measured using SPSV are comparable to those measured using SPIV.

Download Full-text

Particle Image Velocimetry Measurements of Tornado-Like Flow Field in Model WindEEE Dome

Volume 1C, Symposia: Fundamental Issues and Perspectives in Fluid Mechanics; Industrial and Environmental Applications of Fluid Mechanics; Issues and Perspectives in Automotive Flows; Gas-Solid Flows: Dedicated to the Memory of Professor Clayton T. Crowe; Numerical Methods for Multiphase Flow; Transport Phenomena in Energy Conversion From Clean and Sustainable Resources; Transport Phenomena in Materials Processing and Manufacturing Processes ◽

10.1115/fedsm2014-22052 ◽

2014 ◽

Cited By ~ 1

Author(s):

Maryam Refan ◽

Horia Hangan ◽

Kamran Siddiqui

Keyword(s):

Particle Image Velocimetry ◽

Flow Field ◽

Radial Velocity ◽

Particle Image ◽

Tangential Velocity ◽

Scaled Model ◽

Energy And Environment ◽

Radial Profiles ◽

Image Velocimetry ◽

Wide Range

The flow field of tornado vortices simulated in the 1/11 scaled model of the Wind Engineering, Energy and Environment (WindEEE) Dome is characterized. Particle Image Velocimetry measurements were performed to investigate the flow dynamics for a wide range of Swirl ratios (0.12≤S≤1.29) and at various heights above the surface. It is shown that this simulator is capable of generating a wide variety of tornado like vortices ranging from a single-celled laminar vortex to a multi-celled turbulent vortex. Radial profiles of the tangential velocity demonstrated a clear variation in the experimental values with height at and after the touch-down of the breakdown bubble. Also, the comparison between experimental tangential velocities and the Rankine model estimations resulted in good agreement at only the upper levels (Z>0.35). Radial velocity values close to the surface rose as the swirl increased which is mainly due to the intensified tangential velocities in that region. In addition, variation of the radial velocity with height is more noticeable for higher swirls which can be explained by the flow regime being fully turbulent for S≥ 0.57.

Download Full-text