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.

Investigation of Flow Characteristics in a Coronary Artery Stent Using PIV

2003 ◽  
Author(s):  
Lauren K. Yee ◽  
J. R. Kadambi ◽  
Mark P. Wernet
Keyword(s):  
Particle Image ◽  
Flow Characteristics ◽  
Shear Stresses ◽  
Flow Loop ◽  
Relaxation Period ◽  
Micro Particle Image Velocimetry ◽  
Coronary Artery Stent ◽  
Image Velocimetry ◽  
Trailing Edges

The complications resulting from coronary stenting are partly caused by alterations/disturbances in fluid dynamics of the arterial flow. To characterize flow within stented left anterior descending arteries at physiological rest conditions, an in vitro pulsatile flow loop and a micro-particle image velocimetry (PIV) system are developed. The highest and lowest velocities occur at the pumping period peak and the pump relaxation period commencement, respectively. Flow reversal exists at the start of pump relaxation. Recirculation regions at the stent leading and trailing edges and at edges of stent slots correlate to platelet deposition areas. The measured wall shear stresses are 5–15 dynes/cm2, which may inhibit re-endothelialization.

The Effects of Implantation Techniques and Vortex Shedding on Free Emboli Formation in Mechanical Heart Valves

1999 ◽  
Author(s):  
Yanmei Li ◽  
Danny Bluestein
Keyword(s):  
Heart Valves ◽  
Particle Image ◽  
Digital Particle Image Velocimetry ◽  
Implantation Technique ◽  
Jude Medical ◽  
Image Velocimetry ◽  
Suturing Technique ◽  
Implantation Techniques ◽  
Flow Through ◽  
Valve Implantation

Abstract A numerical analysis of pulsatile turbulent flow was conducted past a St. Jude Medical MHV in the aortic position, to study the effects of valve implantation technique on the thromboembolic potential of the valve. The simulation focussed on the assumption that by altering the flow fields past the valves, the valve orientation and the suturing technique employed have a favorable or undesirable effect on the thromboembolic potential of the valve. It was demonstrated that the combination of a valve that is not aligned with the axis of the blood flow and subannularly sutured pledgets, produced accelerating jet flow through the valve orifices and a wider wake of periodic shed vortices in the valve’s leaflets wake. The existence of the shed vortices was confirmed by Digital Particle Image Velocimetry (DPIV). measurements. Platelets paths that exposed the platelets to the highest shear levels led them to entrapment within the shed vortices, indicating that the risk of cardioembolism will be enhance.

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.

Analysis of the Flow Through a Vented Automotive Brake Rotor

2003 ◽  
Vol 125 (6) ◽  
pp. 979-986 ◽  
Author(s):  
David A. Johnson ◽  
Bryan A. Sperandei ◽  
Ross Gilbert
Keyword(s):  
Particle Image ◽  
Radial Flow ◽  
Flow Characteristics ◽  
Suction Side ◽  
Rapid Decay ◽  
Image Velocimetry ◽  
Brake Rotor ◽  
Flow Through ◽  
The Individual ◽  
Automotive Brake

Particle image velocimetry (PIV) was used to measure air velocities through a high solidity radial flow fan utilized as an automotive vented brake rotor. A brake rotor is a somewhat unusual fan in that its sole purpose is not to pump air but to dissipate thermal energy, it has no conventional inlet or outlet housing and it has a continuously varying rotational speed. For three typical rotational speeds, the flow characteristics were captured at the inlet and exit of the rotor, as well as internally through the cooling passages. Inlet measurements showed a swirling entry flow condition with significant misalignment of flow onto the vanes. As a result large regions of flow separation were found in the internal vane-to-vane passages on the suction side surfaces, which would lead to poor heat transfer conditions. The main flow exiting the rotor consisted of a series of jets corresponding to the individual rotor passages and were found to be very unstable leading to a rapid decay in velocity.

scholarly journals Dynamics of transcatheter heart valves with an in vitro experiment incorporating particle image velocimetry

AIP Advances ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 105301
Author(s):  
Li Liu ◽  
Changsong Wu ◽  
Wei Liu ◽  
Wencai Zou ◽  
Yayun Zheng ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Heart Valves ◽  
Particle Image ◽  
Vitro Experiment ◽  
In Vitro Experiment ◽  
Image Velocimetry

Experimental investigation of the influence of the hydraulic performance of an axial blood pump on intraventricular blood flow

2021 ◽  
pp. 039139882110130
Author(s):  
Guang-Mao Liu ◽  
Fu-Qing Jiang ◽  
Xiao-Han Yang ◽  
Run-Jie Wei ◽  
Sheng-Shou Hu
Keyword(s):  
Blood Flow ◽  
Particle Image ◽  
Swirling Flow ◽  
Blood Stasis ◽  
Systemic Circulation ◽  
Operating Conditions ◽  
Blood Pump ◽  
Image Velocimetry ◽  
Ct Data

Blood flow inside the left ventricle (LV) is a concern for blood pump use and contributes to ventricle suction and thromboembolic events. However, few studies have examined blood flow inside the LV after a blood pump was implanted. In this study, in vitro experiments were conducted to emulate the intraventricular blood flow, such as blood flow velocity, the distribution of streamlines, vorticity and the standard deviation of velocity inside the LV during axial blood pump support. A silicone LV reconstructed from computerized tomography (CT) data of a heart failure patient was incorporated into a mock circulatory loop (MCL) to simulate human systemic circulation. Then, the blood flow inside the ventricle was examined by particle image velocimetry (PIV) equipment. The results showed that the operating conditions of the axial blood pump influenced flow patterns within the LV and areas of potential blood stasis, and the intraventricular swirling flow was altered with blood pump support. The presence of vorticity in the LV from the thoracic aorta to the heart apex can provide thorough washing of the LV cavity. The gradually extending stasis region in the central LV with increasing blood pump support is necessary to reduce the thrombosis potential in the LV.

Flow Characteristics of Pressure-Driven Water in Serpentine Micro-Channels

2006 ◽  
Author(s):  
Renqiang Xiong ◽  
J. N. Chung
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Flow Characteristics ◽  
Flow Structures ◽  
Micro Channel ◽  
Pressure Drops ◽  
Micro Particle Image Velocimetry ◽  
Image Velocimetry ◽  
Micro Channels ◽  
Shape And Size

Flow structures and pressure drops were investigated in rectangular serpentine micro-channels with miter bends which had hydraulic diameters of 0.209mm, 0.395mm and 0.549mm respectively. To evaluate the bend effect, the additional pressure drop due to the miter bend must be obtained. Three groups of micro-channels were fabricated to remove the inlet and outlet losses. A validated micro-particle image velocimetry (μPIV) system was used to achieve the flow structure in a serpentine micro-channel with hydraulic diameter of 0.173mm. The experimental results show the vortices around the outer and inner walls of the bend do not form when Re<100. Those vortices appear and continue to develop with the Re number when Re> 100-300, and the shape and size of the vortices almost remain constant when Re>1000. The bend loss coefficient Kb was observed to be related with the Re number when Re<100, with the Re number and channel size when Re>100. It almost keeps constant and changes in the range of ± 10% When Re is larger than some value in 1300-1500. And a size effect on Kb was also observed.

A particle image velocimetry study on the pulsatile flow characteristics in straight tubes with an asymmetric bulge

2000 ◽  
Vol 214 (5) ◽  
pp. 655-671 ◽  
Author(s):  
S C M Yu ◽  
J B Zhao
Keyword(s):  
Particle Image Velocimetry ◽  
Steady Flow ◽  
Pulsatile Flow ◽  
Flow Condition ◽  
Particle Image ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Flow Conditions ◽  
Image Velocimetry

Flow characteristics in straight tubes with an asymmetric bulge have been investigated using particle image velocimetry (PIV) over a range of Reynolds numbers from 600 to 1200 and at a Womersley number of 22. A mixture of glycerine and water (approximately 40:60 by volume) was used as the working fluid. The study was carried out because of their relevance in some aspects of physiological flows, such as arterial flow through a sidewall aneurysm. Results for both steady and pulsatile flow conditions were obtained. It was found that at a steady flow condition, a weak recirculating vortex formed inside the bulge. The recirculation became stronger at higher Reynolds numbers but weaker at larger bulge sizes. The centre of the vortex was located close to the distal neck. At pulsatile flow conditions, the vortex appeared and disappeared at different phases of the cycle, and the sequence was only punctuated by strong forward flow behaviour (near the peak flow condition). In particular, strong flow interactions between the parent tube and the bulge were observed during the deceleration phase. Stents and springs were used to dampen the flow movement inside the bulge. It was found that the recirculation vortex could be eliminated completely in steady flow conditions using both devices. However, under pulsatile flow conditions, flow velocities inside the bulge could not be suppressed completely by both devices, but could be reduced by more than 80 per cent.

scholarly journals Meso-Scale Particle Image Velocimetry Studies of Neurovascular Flows In Vitro

10.3791/58902 ◽  
2018 ◽  
Author(s):  
Ryan A. Peck ◽  
Edver Bahena ◽  
Reza Jahan ◽  
Guillermo Aguilar ◽  
Hideaki Tsutsui ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Image Velocimetry ◽  
Scale Particle ◽  
Meso Scale
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