scholarly journals Analysis of leaflet flutter in biological prosthetic heart valves using PIV measurements

2019 ◽  
Vol 42 ◽  
pp. e41746
Author(s):  
Artur Henrique de Freitas Avelar ◽  
Mairon Assis Guimaris Eller Stófel ◽  
Glenda Dias Vieira ◽  
Jean Andrade Canestri ◽  
Rudolf Huebner
Keyword(s):  
High Speed ◽  
Heart Valves ◽  
Particle Image ◽  
Prosthetic Heart Valves ◽  
Shear Stresses ◽  
Lower Velocity ◽  
Piv Measurements ◽  
Prosthetic Valves ◽  
Image Velocimetry ◽  
Experimental Bench

The use of biological prosthetic valves has increased considerably in recent decades since they have several advantages over mechanical ones, but they still possess the great disadvantage of having a relatively short lifetime. An understudied phenomenon is the flutter effect that causes oscillations in the cusps, which is associated with regurgitation, calcification and fatigue, which can reduce even more the lifetime of bioproteses. In an experimental bench that simulates the cardiac flow, the behavior of a porcine and a bovine pericardium valves was recorded by a high-speed camera to quantify the oscillations of the cusps and an experiment using particle image velocimetry was conducted to study the velocity profiles and shear stresses and their relations with flutter. Results showed that the pericardial valve has lower values of frequencies and amplitudes compared to the porcine valve. Lower velocity values were found in the cusps that did not have flutter, but no relationship was observed between shear stress values and leaflet vibrations. These results may assist in future projects of biological prosthetic valves that have less flutter and longer lifespan.

Flow Visualization Through Two Types of Aortic Prosthetic Heart Valves Using Stereoscopic High-speed Particle Image Velocimetry

2007 ◽  
Vol 31 (12) ◽  
pp. 869-879 ◽  
Author(s):  
Radoslav Kaminsky ◽  
Stephan Kallweit ◽  
Hans-Joachim Weber ◽  
Tom Claessens ◽  
Krzysztof Jozwik ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Visualization ◽  
High Speed ◽  
Heart Valves ◽  
Particle Image ◽  
Prosthetic Heart Valves ◽  
Image Velocimetry

PIV Measurements of Turbulent Flow in a Channel With Solid or Perforated Ribs

2010 ◽  
Author(s):  
Lei Wang ◽  
Mirko Salewski ◽  
Bengt Sunde´n
Keyword(s):  
Shear Stress ◽  
Particle Image ◽  
Reynolds Shear Stress ◽  
Area Ratio ◽  
Shear Stresses ◽  
Open Area ◽  
Reattachment Length ◽  
Mean Velocity ◽  
Piv Measurements ◽  
Image Velocimetry

Particle image velocimetry measurements are performed in a channel with periodic ribs on one wall. We investigate the flow around two different rib configurations: solid and perforated ribs with a slit. The ribs obstruct the channel by 20% of its height and are arranged 10 rib heights apart. For the perforated ribs, the slit height is 20% of the rib height, and the open-area ratio is 16%. We discuss the flow in terms of mean velocity, streamlines, vorticity, turbulence intensity, and Reynolds shear stress. We find that the recirculation bubbles after the perforated ribs are significantly smaller than those after the solid ribs. The reattachment length after perforated ribs is smaller by about 45% compared with the solid ribs. In addition, the Reynolds shear stresses around the perforated ribs are significantly smaller than in the solid rib case, leading to a reduction of the pressure loss in the perforated rib case.

Flow Characteristics Inside a Transpatent Flexible Left Ventricle With Anatomical and Antianatomical Valve Orientation

2001 ◽  
Author(s):  
Olga Pierrakos ◽  
Pavlos P. Vlachos ◽  
Demetri P. Telionis
Keyword(s):  
Heart Valves ◽  
Particle Image ◽  
Flow Characteristics ◽  
Shear Stresses ◽  
Pathological Conditions ◽  
Image Velocimetry ◽  
Flow Through ◽  
Blood Elements ◽  
The Ideal

Abstract Mechanical heart valves (MHV) and the operation of heart valve replacement have evolved to a level of universal acceptance and yet, MHV implantation is not always the ideal solution. Apparently the flow through pivoted leaflets of MHVs induces a combination of flow characteristics, which are clearly conducive to clot formation and can initiate many other pathological conditions. Most in vitro studies of the flow downstream of a MHV have been conducted with the valve in the aortic position (i.e. Reul et al., 1986). Bluestein et al., (2000) used a numerical simulation and Digital Particle-Image Velocimetry (DPIV) to reveal intricate patterns of interacting shed vortices downstream of the aortic valve and demonstrated that blood elements exposed to the highest shear stresses in the immediate proximity of the MHV could be trapped within the vortices that form in the wake of the valve.

scholarly journals Aerodynamics of manoeuvring flight in brown long-eared bats ( Plecotus auritus )

2018 ◽  
Vol 15 (148) ◽  
pp. 20180441 ◽  
Author(s):  
Per Henningsson ◽  
Lasse Jakobsen ◽  
Anders Hedenström
Keyword(s):  
Particle Image Velocimetry ◽  
Wind Tunnel ◽  
High Speed ◽  
Particle Image ◽  
Future Studies ◽  
Image Velocimetry ◽  
Mechanistic Basis

In this study, we explicitly examine the aerodynamics of manoeuvring flight in animals. We studied brown long-eared bats flying in a wind tunnel while performing basic sideways manoeuvres. We used particle image velocimetry in combination with high-speed filming to link aerodynamics and kinematics to understand the mechanistic basis of manoeuvres. We predicted that the bats would primarily use the downstroke to generate the asymmetries for the manoeuvre since it has been shown previously that the majority of forces are generated during this phase of the wingbeat. We found instead that the bats more often used the upstroke than they used the downstroke for this. We also found that the bats used both drag/thrust-based and lift-based asymmetries to perform the manoeuvre and that they even frequently switch between these within the course of a manoeuvre. We conclude that the bats used three main modes: lift asymmetries during downstroke, thrust/drag asymmetries during downstroke and thrust/drag asymmetries during upstroke. For future studies, we hypothesize that lift asymmetries are used for fast turns and thrust/drag for slow turns and that the choice between up- and downstroke depends on the timing of when the bat needs to generate asymmetries.

scholarly journals Dual-camera system for high-speed imaging in particle image velocimetry

2012 ◽  
Vol 15 (3) ◽  
pp. 193-195 ◽  
Author(s):  
K. Hashimoto ◽  
A. Hori ◽  
T. Hara ◽  
S. Onogi ◽  
H. Mouri
Keyword(s):  
Particle Image Velocimetry ◽  
High Speed ◽  
Particle Image ◽  
High Speed Imaging ◽  
Camera System ◽  
Image Velocimetry

PIV Measurements Within the Waves of Wavy and Wavy-Annular Horizontal Two-Phase Flow

2005 ◽  
Author(s):  
R. E. Foster ◽  
T. A. Shedd
Keyword(s):  
Particle Image ◽  
Image Processing Algorithm ◽  
Two Phase ◽  
Piv Measurements ◽  
Post Process ◽  
Image Velocimetry ◽  
Processed Form ◽  
Image Pairs ◽  
Particle Images ◽  
The Waves

A novel technique of microscopic Particle Image Velocimetry (PIV) is presented for two-phase annular, wavy-annular and stratified flow. Seeding of opaque particles in a water/dye flow allows the acquisition of instantaneous film velocity data in the film cross-section at the center of the tube in the form of digital image pairs. An image processing algorithm is also described that allows numerical velocities to be distilled from particle images by commercial PIV software. The approach yields promising results for stratified and wavy-annular flows, however highly bubbly flows remain difficult to image and post-process. Initial data images are presented in raw and processed form.

Time-Resolved Particle Image Velocimetry (PIV) Measurements in a Radial Diffuser Pump

2009 ◽  
Author(s):  
Jianjun Feng ◽  
Friedrich-Karl Benra ◽  
Hans Josef Dohmen
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Time Resolved ◽  
Piv Measurements ◽  
Part Load ◽  
Channel Characteristic ◽  
Image Velocimetry ◽  
Pump Stage ◽  
Low Specific Speed ◽  
Load Conditions

The truly time-variant unsteady flow in a low specific speed radial diffuser pump stage has been investigated by time-resolved Particle Image Velocimetry (PIV) measurements. The measurements are conducted at the midspan of the blades for the design condition and also for some severe part-load conditions. The instantaneous flow fields among different impeller channels are analyzed and compared in detail, and more attention has been paid to flow separations at part-load conditions. The analysis of the measured results shows that the flow separations at two adjacent impeller channels are quite different at some part-load conditions. The separations generally exhibit a two-channel characteristic.

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