Characterizing the HeartMate II Left Ventricular Assist Device Outflow Using Particle Image Velocimetry

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Grant W. Rowlands ◽  
Bryan C. Good ◽  
Steven Deutsch ◽  
Keefe B. Manning
Keyword(s):  
Particle Image Velocimetry ◽  
Steady Flow ◽  
Flow Rate ◽  
Particle Image ◽  
Left Ventricular ◽  
Reynolds Stresses ◽  
Heartmate Ii ◽  
Ventricular Assist ◽  
Image Velocimetry ◽  
Von Willebrand

Ventricular assist devices (VADs) are implanted in patients with a diseased ventricle to maintain peripheral perfusion as a bridge-to-transplant or as destination therapy. However, some patients with continuous flow VADs (e.g., HeartMate II (HMII)) have experienced gastrointestinal (GI) bleeding, in part caused by the proteolytic cleavage or mechanical destruction of von Willebrand factor (vWF), a clotting glycoprotein. in vitro studies were performed to measure the flow located within the HMII outlet cannula under both steady and physiological conditions using particle image velocimetry (PIV). Under steady flow, a mock flow loop was used with the HMII producing a flow rate of 3.2 L/min. The physiological experiment included a pulsatile pump operated at 105 BPM with a ventricle filling volume of 50 mL and in conjunction with the HMII producing a total flow rate of 5.0 L/min. Velocity fields, Reynolds normal stresses (RNSs), and Reynolds shear stresses (RSSs) were analyzed to quantify the outlet flow's potential contribution to vWF degradation. Under both flow conditions, the HMII generated principal Reynolds stresses that are, at times, orders of magnitude higher than those needed to unfurl vWF, potentially impacting its physiological function. Under steady flow, principal RNSs were calculated to be approximately 500 Pa in the outlet cannula. Elevated Reynolds stresses were observed throughout every phase of the cardiac cycle under physiological flow with principal RNSs approaching 1500 Pa during peak systole. Prolonged exposure to these conditions may lead to acquired von Willebrand syndrome (AvWS), which is accompanied by uncontrollable bleeding episodes.

Experimental Investigation of Flow Blurring Atomizer at Near Field Using Particle Image Velocimetry

2019 ◽  
Author(s):  
Raju Murugan ◽  
Dhanalakshmi Sellan ◽  
Pankaj S. Kolhe
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Rate ◽  
Liquid Flow ◽  
Particle Image ◽  
Liquid Flow Rate ◽  
Diagnostic Technique ◽  
Reynolds Stresses ◽  
Full Field ◽  
Image Velocimetry ◽  
Spray Droplets

Abstract Two-fluid flow blurring atomization is characterized by the backflow recirculation of the air phase in the liquid pipe by bifurcation of the liquid and airflow. Most of the primary spray process is completed in the injector due to the penetration of air into the liquid tube. Thus, the majority of the liquid ligaments are converted into a fine spray at the outlet of the nozzle. Experiments were performed with two different air to liquid ratios (0.6 and 1) by mass, where water is considered as the liquid and airflow was kept constant (0.2 g/s). To change the ALR, the liquid flow rate was changed. Particle image velocimetry (PIV) diagnostic technique provides the full-field velocity of the spray droplets (discrete phase). It may be noted that sprays are self-seeded and PIV measurements reflect the droplet velocities instead of air velocity. To understand the effect of the spatial resolution of PIV on spray droplet velocity; experiments were conducted at three different spatial resolutions (11.8, 16.4 and 23.22 μm/pixel) for each ALR. As the ALR is increased, the mass of the liquid in the spray decreases, resulting in finer atomization and velocity of the spray droplets. This means that finer droplets are generated for the same mass of air at a lower liquid flow rate as compared to higher liquid flow rate. Note that Reynolds stresses provide an indication of the turbulent breakup of the droplet and larger magnitudes observed for higher ALR indicate finer atomization.

scholarly journals Validation of numerically simulated ventricular flow patterns during left ventricular assist device support

2020 ◽  
Vol 44 (1) ◽  
pp. 30-38 ◽  
Author(s):  
Mojgan Ghodrati ◽  
Thananya Khienwad ◽  
Alexander Maurer ◽  
Francesco Moscato ◽  
Francesco Zonta ◽  
...  
Keyword(s):  
Shear Stress ◽  
Particle Image Velocimetry ◽  
Particle Image ◽  
Fluid Dynamic ◽  
Flow Patterns ◽  
Left Ventricular ◽  
Dynamic Simulations ◽  
Ventricular Assist ◽  
Shear Stress Transport ◽  
Image Velocimetry

Intraventricular flow patterns during left ventricular assist device support have been investigated via computational fluid dynamics by several groups. Based on such simulations, specific parameters for thrombus formation risk analysis have been developed. However, computational fluid dynamic simulations of complex flow configurations require proper validation by experiments. To meet this need, a ventricular model with a well-defined inflow section was analyzed by particle image velocimetry and replicated by transient computational fluid dynamic simulations. To cover the laminar, transitional, and turbulent flow regime, four numerical methods including the laminar, standard k-omega, shear-stress transport, and renormalized group k-epsilon were applied and compared to the particle image velocimetry results in 46 different planes in the whole left ventricle. The simulated flow patterns for all methods, except renormalized group k-epsilon, were comparable to the flow patterns measured using particle image velocimetry (absolute error over whole left ventricle: laminar: 10.5, standard k-omega: 11.3, shear–stress transport: 11.3, and renormalized group k-epsilon: 17.8 mm/s). Intraventricular flow fields were simulated using four numerical methods and validated with experimental particle image velocimetry results. In the given setting and for the chosen boundary conditions, the laminar, standard K-omega, and shear–stress transport methods showed acceptable similarity to experimental particle image velocimetry data, with the laminar model showing the best transient behavior.

scholarly journals Methods for determination of stagnation in pneumatic ventricular assist devices

2018 ◽  
Vol 41 (10) ◽  
pp. 653-663 ◽  
Author(s):  
Damian Obidowski ◽  
Piotr Reorowicz ◽  
Dariusz Witkowski ◽  
Krzysztof Sobczak ◽  
Krzysztof Jóźwik
Keyword(s):  
Particle Image Velocimetry ◽  
Ventricular Assist Device ◽  
Particle Image ◽  
Single Case ◽  
Ventricular Assist Devices ◽  
Assist Device ◽  
Single Experiment ◽  
Ventricular Assist ◽  
University Of Technology ◽  
Image Velocimetry

Background: A pneumatic paediatric ventricular assist device developed at the Foundation of Cardiac Surgery Development, Zabrze, equipped with valves based on J. Moll’s design, with later modifications introduced at the Institute of Turbomachinery, Lodz University of Technology, was tested numerically and experimentally. The main aim of those investigations was to detect stagnation zones within the ventricular assist device and indicate advantages and limitations of both approaches. Methods: In the numerical transient test, a motion of the diaphragm and discs was simulated. Two different methods were used to illustrate stagnation zones in the ventricular assist device. The flow pattern inside the chamber was represented by velocity contours and vectors to validate the results using images obtained in the laser particle image velocimetry experiment. Results: The experimental light-based method implied problems with proper illumination of regions in the wall vicinity. High-resolution flow data and other important parameters as stagnation regions or flow patterns in regions not accessible for light in the particle image velocimetry method are derived in the numerical solution. However, computations of a single case are much more time-consuming if compared to a single experiment conducted on a well-calibrated stand. Conclusion: The resulting main vortexes in the central part of the pump chamber and the velocity magnitudes are correlated in both methods, which are complementary and when used together offer better insight into the flow structure inside the ventricular assist device and enable a deeper analysis of the results.

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 Particle image velocimetry measurements of induced separation at the leading edge of a plate

2016 ◽  
Vol 804 ◽  
pp. 278-297 ◽  
Author(s):  
J. P. J. Stevenson ◽  
K. P. Nolan ◽  
E. J. Walsh
Keyword(s):  
Particle Image Velocimetry ◽  
Shear Layer ◽  
Particle Image ◽  
Reverse Flow ◽  
Leading Edge ◽  
Quadrant Analysis ◽  
Bypass Transition ◽  
Reynolds Stresses ◽  
Free Stream Turbulence ◽  
Image Velocimetry

The free shear layer that separates from the leading edge of a round-nosed plate has been studied under conditions of low (background) and elevated (grid-generated) free stream turbulence (FST) using high-fidelity particle image velocimetry. Transition occurs after separation in each case, followed by reattachment to the flat surface of the plate downstream. A bubble of reverse flow is thereby formed. First, we find that, under elevated (7 %) FST, the time-mean bubble is almost threefold shorter due to an accelerated transition of the shear layer. Quadrant analysis of the Reynolds stresses reveals the presence of slender, highly coherent fluctuations amid the laminar part of the shear layer that are reminiscent of the boundary-layer streaks seen in bypass transition. Instability and the roll-up of vortices then follow near the crest of the shear layer. These vortices are also present under low FST and in both cases are found to make significant contributions to the production of Reynolds stress over the rear of the bubble. But their role in reattachment, whilst important, is not yet fully clear. Instantaneous flow fields from the low-FST case reveal that the bubble of reverse flow often breaks up into two or more parts, thereby complicating the overall reattachment process. We therefore suggest that the downstream end of the ‘separation isoline’ (the locus of zero absolute streamwise velocity that extends unbroken from the leading edge) be used to define the instantaneous reattachment point. A histogram of this point is found to be bimodal: the upstream peak coincides with the location of roll-up, whereas the downstream mode may suggest a ‘flapping’ motion.

Particle Image Velocimetry Experiment and Computational Fluid Dynamics Simulation of Flow Around Rigid Cylinder

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Guangyao Wang ◽  
Ye Tian ◽  
Spyros A. Kinnas
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Particle Image Velocimetry ◽  
Vector Fields ◽  
Particle Image ◽  
Cfd Simulation ◽  
Dynamics Simulation ◽  
Reynolds Stresses ◽  
Rigid Cylinder ◽  
Image Velocimetry

This work focuses on the study of the flow around a rigid cylinder with both particle image velocimetry (PIV) experiment and computational fluid dynamics (CFD) simulation. PIV measurements of the flow field downstream of the cylinder are first presented. The boundary conditions for CFD simulations are measured in the PIV experiment. Then the PIV flow is compared with both Reynolds-averaged Navier–Stokes (RANS) two-dimensional (2D) and large eddy simulation (LES) three-dimensional (3D) simulations performed with ANSYS fluent. The velocity vector fields and time histories of velocity are analyzed. In addition, the time-averaged velocity profiles and Reynolds stresses are analyzed. It is found that, in general, LES (3D) gives a better prediction of flow characteristics than RANS (2D).

Particle-Image Velocimetry Study of a Pediatric Ventricular Assist Device

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
E. Ferrara ◽  
M. Muramatsu ◽  
K. T. Christensen ◽  
I. A. Cestari
Keyword(s):  
Particle Image Velocimetry ◽  
Ventricular Assist Device ◽  
Particle Image ◽  
Thrombus Formation ◽  
Test Fluid ◽  
Polystyrene Spheres ◽  
Assist Device ◽  
Ventricular Assist ◽  
Strong Turbulence ◽  
Image Velocimetry

Particle-image velocimetry (PIV) was used to visualize the flow within an optically transparent pediatric ventricular assist device (PVAD) under development in our laboratory. The device studied is a diaphragm type pulsatile pump with an ejection volume of 30 ml per beating cycle intended for temporary cardiac assistance as a bridge to transplantation or recovery in children. Of particular interest was the identification of flow patterns, including regions of stagnation and/or strong turbulence that often promote thrombus formation and hemolysis, which can degrade the usefulness of such devices. For this purpose, phase-locked PIV measurements were performed in planes parallel to the diaphram that drives the flow in the device. The test fluid was seeded with 10 μm polystyrene spheres, and the motion of these particles was used to determine the instantaneous flow velocity distribution in the illumination plane. These measurements revealed that flow velocities up to 1.0 m/s can occur within the PVAD. Phase-averaged velocity fields revealed the fixed vortices that drive the bulk flow within the device, though significant cycle-to-cycle variability was also quite apparent in the instantaneous velocity distributions, most notably during the filling phase. This cycle-to-cycle variability can generate strong turbulence that may contribute to greater hemolysis. Stagnation regions have also been observed between the input and output branches of the prototype, which can increase the likelihood of thrombus formation.

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