Time-Resolved DPIV Analysis of Vortex Dynamics in a Left Ventricular Model Through Bileaflet Mechanical and Porcine Heart Valve Prostheses

2004 ◽  
Vol 126 (6) ◽  
pp. 714-726 ◽  
Author(s):  
Olga Pierrakos ◽  
Pavlos P. Vlachos ◽  
Demetri P. Telionis
Keyword(s):  
Mitral Valve ◽  
Vortex Formation ◽  
Flow Patterns ◽  
Left Ventricular ◽  
Time Resolved ◽  
Vortical Structures ◽  
Jude Medical ◽  
Image Velocimetry ◽  
Valve Prostheses ◽  
Physical Phenomena

The performance of the heart after a mitral valve replacement operation greatly depends on the flow character downstream of the valve. The design and implanting orientation of valves may considerably affect the flow development. A study of the hemodynamics of two orientations, anatomical and anti-anatomical, of the St. Jude Medical (SJM) bileaflet valve are presented and compared with those of the SJM Biocor porcine valve, which served also to represent the natural valve. We document the velocity field in a flexible, transparent (LV) using time-resolved digital particle image velocimetry (TRDPIV). Vortex formation and vortex interaction are two important physical phenomena that dominate the filling and emptying of the ventricle. For the three configurations, the following effects were examined: mitral valve inlet jet asymmetry, survival of vortical structures upstream of the aortic valve, vortex-induced velocities and redirection of the flow in abidance of the Biot–Savart law, domain segmentation, resonant times of vortical structures, and regions of stagnant flow. The presence of three distinct flow patterns, for the three configurations, was identified by the location of vortical structures and level of coherence corresponding to a significant variation in the turbulence level distribution inside the LV. The adverse effect of these observations could potentially compromise the efficiency of the LV and result in flow patterns that deviate from those in the natural heart.

Replication of left ventricular haemodynamics with a simple planar mitral valve model

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Anna Daub ◽  
Jochen Kriegseis ◽  
Bettina Frohnapfel
Keyword(s):  
Mitral Valve ◽  
Computational Models ◽  
Vortex Formation ◽  
Flow Characteristics ◽  
Left Ventricular ◽  
Computational Effort ◽  
Type Model ◽  
Diastolic Phase ◽  
Valve Model ◽  
Modelling Approach

AbstractTools for the numerical prediction of haemodynamics in multi-disciplinary integrated heart simulations have to be based on computational models that can be solved with low computational effort and still provide physiological flow characteristics. In this context the mitral valve model is important since it strongly influences the flow kinematics, especially during the diastolic phase. In contrast to a 3D valve, a vastly simplified valve model in form of a simple diode is known to be unable to reproduce the characteristic vortex formation and unable to promote a proper ventricular washout. In the present study, an adaptation of the widely used simplest modelling approach for the mitral valve is employed and compared to a physiologically inspired 3D valve within the same ventricular geometry. The adapted approach shows enhanced vortex formation and an improved ventricular washout in comparison to the diode type model. It further shows a high potential in reproducing the main flow characteristics and related particle residence times generated by a 3D valve.

Effects of Orientation and Position of the Combustor-Turbine Interface on the Cooling of a Vane Endwall

2011 ◽  
Author(s):  
A. A. Thrift ◽  
K. A. Thole ◽  
S. Hada
Keyword(s):  
Film Cooling ◽  
Guide Vane ◽  
Vortex Formation ◽  
Horseshoe Vortex ◽  
Time Resolved ◽  
Image Velocimetry ◽  
Thermal Measurements ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Stagnation Plane

First stage, nozzle guide vanes and accompanying endwalls are extensively cooled by the use of film cooling through discrete holes and leakage flow from the combustor-turbine interface gap. While there are cooling benefits from the interface gap, it is generally not considered as part of the cooling scheme. This paper reports on the effects of the position and orientation of a two-dimensional slot on the cooling performance of a nozzle guide vane endwall. In addition to surface thermal measurements, time-resolved, digital particle image velocimetry (TRDPIV) measurements were performed at the vane stagnation plane. Two slot orientations, 90° and 45°, and three streamwise positions were studied. Effectiveness results indicate a significant increase in area averaged effectiveness for the 45° slot relative to the 90° orientation. Flowfield measurements show dramatic differences in the horseshoe vortex formation.

Model Studies at Mechanical Aortic Heart Valve Prostheses—Part I: Steady-State Flow Fields and Pressure Loss Coefficients

1988 ◽  
Vol 110 (4) ◽  
pp. 334-343 ◽  
Author(s):  
Martin Knoch ◽  
Helmut Reul ◽  
Ralf Kro¨ger ◽  
Gu¨nter Rau
Keyword(s):  
Heart Valve ◽  
Vortex Formation ◽  
Flow Fields ◽  
Turbulent Shear ◽  
Human Aorta ◽  
Shear Stresses ◽  
Scaled Model ◽  
Jude Medical ◽  
Heart Valve Prostheses ◽  
Valve Prostheses

In a 3:1 scaled model of the human aorta models of the Omniscience, Bjo¨rk-Shiley Convexo-Concave, Bjo¨rk-Shiley Monostrut, Medtronic-Hall, Duromedics (Hemex) and the Saint Jude Medical heart valve prostheses are studied in steady flow representing the systolic peak flow phase. Detailed flow visualization experiments show flow separations at all inner ring surfaces as well as at most of the occluders. The resulting stagnation areas increase the risk of thrombus accumulation. Flow separations also stimulate vortex formation and turbulent mixing at the downstream jet boundaries and thus may intensify blood damage by turbulent shear stresses. The different influences of struts and occluder guides on the flow around the occluders are discussed. The effects of the individual valve components on the flow fields are analyzed and correlated with the resulting pressure losses.

scholarly journals Effects of the atrium on intraventricular flow patterns during mechanical circulatory support

2021 ◽  
pp. 039139882110560
Author(s):  
Mojgan Ghodrati ◽  
Thomas Schlöglhofer ◽  
Alexander Maurer ◽  
Thananya Khienwad ◽  
Daniel Zimpfer ◽  
...  
Keyword(s):  
Shear Stress ◽  
Mitral Valve ◽  
Residence Time ◽  
Flow Patterns ◽  
Left Ventricular ◽  
Circulatory Support ◽  
Low Velocity ◽  
Ventricular Assist ◽  
Intraventricular Flow ◽  
Blood Flow Dynamics

Simulations of the ventricular flow patterns during left ventricular assist device (LVAD) support are mainly performed with idealized cylindrical inflow, neglecting the influence of the atrial vortex. In this study, the influence of the left atrium (LA) on the intra-ventricular flow was investigated via Computational Fluid Dynamics (CFD) simulations. Ventricular flow was simulated by a combined Eulerian (carrier flow)/Lagrangian (particles) approach taking into account either the LA or a cylindrical inflow section to mimic a fully support condition. The flow deviation at the mitral valve, the blood low-velocity volume as well as the residence time and shear stress history of the particles were calculated. Inclusion of the LA deflects the flow at the mitral valve by 25°, resulting in an asymmetric flow jet entering the left ventricle. This reduced the ventricular low-velocity volume by 40% (from 6.4 to 3.9 cm3), increased (40%) the shear stress experienced by particles and correspondingly increased (27%) their residence time. Under the studied conditions, the atrial geometry plays a major role in the development of intraventricular flow patterns. A reliable prediction of blood flow dynamics and consequently thrombosis risk analysis within the ventricle requires the consideration of the LA in computational simulations.

scholarly journals Evaluation of patients with a HeartMate 3 left ventricular assist device using echocardiographic particle image velocimetry

2020 ◽  
Author(s):  
Arend F. L. Schinkel ◽  
Sakir Akin ◽  
Mihai Strachinaru ◽  
Rahatullah Muslem ◽  
Dan Bowen ◽  
...  
Keyword(s):  
Blood Flow ◽  
Particle Image Velocimetry ◽  
Particle Image ◽  
Vortex Formation ◽  
Left Ventricular ◽  
Flow Dynamics ◽  
Lv Function ◽  
Image Velocimetry ◽  
Intraventricular Flow ◽  
Blood Flow Dynamics

Abstract Purpose Poor left ventricular (LV) function may affect the physiological intraventricular blood flow and physiological vortex formation. The aim of this study was to investigate the pattern of intraventricular blood flow dynamics in patients with LV assist devices (LVADs) using echocardiographic particle image velocimetry. Materials and methods This prospective study included 17 patients (mean age 57 ± 11 years, 82% male) who had received an LVAD (HeartMate 3, Abbott Laboratories, Chicago, Illinois, USA) because of end-stage heart failure and poor LV function. Eleven (64%) patients had ischemic cardiomyopathy, and six patients (36%) had nonischemic cardiomyopathy. All patients underwent echocardiography, including intravenous administration of an ultrasound-enhancing agent (SonoVue, Bracco, Milan, Italy). Echocardiographic particle image velocimetry was used to quantify LV blood flow dynamics, including vortex formation (Hyperflow software, Tomtec imaging systems Gmbh, Unterschleissheim, Germany). Results Contrast-enhanced ultrasound was well tolerated in all patients and was performed without adverse reactions or side effects. The LVAD function parameters did not change during or after the ultrasound examination. The LVAD flow was on average 4.3 ± 0.3 L/min, and the speed was 5247 ± 109 rotations/min. The quantification of LV intraventricular flow demonstrated substantial impairment of vortex parameters. The energy dissipation, vorticity, and kinetic energy fluctuation indices were severely impaired. Conclusions Echo particle velocimetry is safe and feasible for the quantitative assessment of intraventricular flow in patients with an LVAD. The intraventricular LV flow and vortex parameters are severely impaired in these patients.

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