A Coupled Overlapping Domain Method for the Computation of Transitional Flow Through Artificial Heart Valves

2012 ◽  
Author(s):  
A. C. Verkaik ◽  
A. C. B. Bogaerds ◽  
F. Storti ◽  
F. N. van de Vosse
Keyword(s):  
High Speed ◽  
Heart Valves ◽  
Reynolds Numbers ◽  
Transitional Flow ◽  
Small Scale ◽  
High Deformation ◽  
Artificial Heart Valves ◽  
Laminar And Turbulent Flow ◽  
Flow Through ◽  
Dependent Flow

When blood is pumped through the aortic valves, it has a time dependent flow with a relatively high speed, resulting in Reynolds numbers between 1500 and 3000. Hence, flow is in the transitional regime between laminar and turbulent flow. Transitional flow contains small scale fluctuations, see Figure 1, and may result in local high deformation rates.

scholarly journals Numerical Study of Blood Flow Through Artificial Heart Valves

2021 ◽  
Vol 1094 (1) ◽  
pp. 012120
Author(s):  
Hussein Togun ◽  
Ali Abdul Hussain ◽  
Saja Ahmed ◽  
Iman Abdul hussain ◽  
Huda Shaker
Keyword(s):  
Blood Flow ◽  
Artificial Heart ◽  
Heart Valves ◽  
Numerical Study ◽  
Artificial Heart Valves ◽  
Flow Through

Axisymmetric Flow in a Motored Reciprocating Engine

1978 ◽  
Vol 192 (1) ◽  
pp. 213-223 ◽  
Author(s):  
A. D. Gosman ◽  
A. Melling ◽  
J. H. Whitelaw ◽  
P. Watkins
Keyword(s):  
Laser Doppler Anemometry ◽  
Axisymmetric Flow ◽  
Flow Characteristics ◽  
Small Scale ◽  
Mean Velocity ◽  
Inlet Velocity ◽  
Reciprocating Engine ◽  
Laminar And Turbulent Flow ◽  
Flow Through ◽  
The Mean

A study was made of axisymmetric, laminar and turbulent flow in a motored reciprocating engine with flow through a cylinder head port. Measurements were obtained by laser-Doppler anemometry and predictions for the laminar case were generated by finite-difference means. Agreement between calculated and measured results is good for the main features of the flow field, but significant small scale differences exist, due partly to uncertainties in the inlet velocity distribution. The measurements show, for example, that the mean velocity field is influenced more strongly by the engine geometry than by the speed. In general, the results confirm that the calculation method can be used to represent the flow characteristics of motored reciprocating engines without compression and suggest that extensions to include compression and combustion are within reach.

A Method to Measure the Station of Artificial Mechanical Heart Valves

2013 ◽  
Vol 683 ◽  
pp. 712-715
Author(s):  
Feng Zhou ◽  
Liang Liang Wu ◽  
Yuan Yuan Cui ◽  
Ying Chen ◽  
Jie Yang ◽  
...  
Keyword(s):  
High Speed ◽  
Heart Valves ◽  
Ultrasonic Method ◽  
High Speed Photography ◽  
In Vitro Experiments ◽  
In Vivo Experiments ◽  
Artificial Heart Valves ◽  
Economic Injury

The experiments of artificial heart valves were divided into in vivo and in vitro experiments; in vivo experiments provide accurate experimental parameters serving in vitro research. Simulation experiment used in vitro usually goes like this, firstly design a similar model or prototype phenomenon, then analysis the model working out the regular parameters related to the process, ruled out the possibility of impact on the study of individual exist in vivo experiment. In vitro experiments are likely designed; performance can be simplified and prominently concerned about contents, even designed some extreme conditions to test. A number of means related to fluid experimental measurement are included, such as the Particle Image Velocimetry（PIV）[1], Dual Catheter Method [2]，and ultrasonic method[3] and so on. However, these methods have different kinds of limitations, for example the Dual Catheter Method cannot be used as a routine determination for clinic due to its destructiveness, and PIV test requires expensive equipment. This study was designed by the image processing technology of high-speed photography aiming at the production of a reliable, simple, economic, injury-free and non-contact measurement method.

Experimental Measurements of the Flow-Induced Shear Stress Distribution in the Vicinity of Prosthetic Heart Valves

1981 ◽  
Vol 103 (4) ◽  
pp. 267-274 ◽  
Author(s):  
W. H. Herkes ◽  
J. R. Lloyd
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Test Section ◽  
Heart Valves ◽  
Reynolds Numbers ◽  
Shear Stress Distribution ◽  
Electrochemical Technique ◽  
Prosthetic Heart Valves ◽  
Disk Valve ◽  
Flow Through

The present study examines the local shear stress distribution occurring during flow through prosthetic valves. The electrochemical technique is a powerful tool for the study of mass transfer related phenomena and was selected for this investigation. The present investigation attempts to establish the viability of the particular application of the technique. Three test section geometries were analyzed: a straight tube, a ball-in-cage valve, and a model disk-in-cage valve, and the tests were conducted at six Reynolds numbers ranging from 1000 to 6000 under steady-state conditions. The model disk valve provided a base-case check on the validity of the technique since it has been employed in several previous studies and the flow through it is well documented. High shear and low shear regions are clearly evident and their locations can be pinpointed. The ball-in-cage valve was tested over the full range of Reynolds numbers. The shear profiles demonstrate a double peak in the region of the ball, a result which was unexpected. Careful study revealed that this was a result of the test section geometry and provides another demonstration of the importance of test section geometry. The frequency of the fluctuations in wall shear for the ball valve were found to be different than those for the disk valve indicating that the environment at the aortic wall is definitely affected by valve design. This study showed the electrochemical technique to be a valuable tool for the study of the flow through prosthetic heart valves.

A Comparison of Predicted and Measured Friction Factors for Turbulent Flow Through Rectangular Ducts

1962 ◽  
Vol 84 (1) ◽  
pp. 82-88 ◽  
Author(s):  
J. P. Hartnett ◽  
J. C. Y. Koh ◽  
S. T. McComas
Keyword(s):  
Friction Coefficient ◽  
Turbulent Flow ◽  
Reynolds Numbers ◽  
Square Duct ◽  
Aspect Ratios ◽  
Friction Factors ◽  
Rectangular Channels ◽  
Laminar And Turbulent Flow ◽  
Flow Through ◽  
Predicted Values

The friction coefficient for both laminar and turbulent flow through rectangular channels was analytically and experimentally studied. The analytic expression for the pressure loss in fully established laminar flow was verified by experiment. In turbulent flow, the method of Deissler and Taylor was used to calculate the friction coefficient. The calculated and measured results were in agreement for ducts having large aspect ratios. At aspect ratios less than 5:1, the predicted values of the friction factors were lower than the experimental data, with a maximum difference of 12 per cent evident for the square duct. It was found that the circular-tube correlation accurately predicts the friction coefficient for flow through rectangular ducts of any aspect ratio for Reynolds numbers between 6 × 103 and 5 × 105. Hydrodynamic entrance-length results are also presented in the laminar and turbulent flow ranges for both a smooth and an abrupt entrance configuration.

Turbulent dynamics of pipe flow captured in a reduced model: puff relaminarization and localized ‘edge’ states

2009 ◽  
Vol 619 ◽  
pp. 213-233 ◽  
Author(s):  
ASHLEY P. WILLIS ◽  
RICH R. KERSWELL
Keyword(s):  
Pipe Flow ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Edge State ◽  
Travelling Wave ◽  
Edge States ◽  
Huge Number ◽  
Laminar And Turbulent Flow ◽  
Flow Through

Fully three-dimensional computations of flow through a long pipe demand a huge number of degrees of freedom, making it very expensive to explore parameter space and difficult to isolate the structure of the underlying dynamics. We therefore introduce a ‘2+ε-dimensional’ model of pipe flow, which is a minimal three-dimensionalization of the axisymmetric case: only sinusoidal variation in azimuth plus azimuthal shifts are retained; yet the same dynamics familiar from experiments are found. In particular the model retains the subcritical dynamics of fully resolved pipe flow, capturing realistic localized ‘puff-like’ structures which can decay abruptly after long times, as well as global ‘slug’ turbulence. Relaminarization statistics of puffs reproduce the memoryless feature of pipe flow and indicate the existence of a Reynolds number about which lifetimes diverge rapidly, provided that the pipe is sufficiently long. Exponential divergence of the lifetime is prevalent in shorter periodic domains. In a short pipe, exact travelling-wave solutions are found near flow trajectories on the boundary between laminar and turbulent flow. In a long pipe, the attracting state on the laminar–turbulent boundary is a localized structure which resembles a smoothened puff. This ‘edge’ state remains localized even for Reynolds numbers at which the turbulent state is global.

A Finite-Element Study of Newtonian and Power-Law Fluids in Conical Channel Flow

1997 ◽  
Vol 119 (2) ◽  
pp. 341-346 ◽  
Author(s):  
S. H. Garrioch ◽  
D. F. James
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Conical Flow ◽  
Shear Thinning Fluids ◽  
Conical Channel ◽  
Power Law Fluids ◽  
Converging Flow ◽  
Flow Through ◽  
Converging Flow Rheometer

A numerical study of Newtonian and shear-thinning fluids in high-speed, laminar flow through a conical channel is presented. Using a variety of cone-angles and Reynolds numbers on the order of 100, converging flow is mapped according to several characteristics: the angle at which separation occurs at the cone outlet, the extent to which sink-flow is approximated, and the pressure drop through the cone. While the data provides a fundamental description of conical flow, it may be of particular usefulness to rheologists in establishing an inelastic baseline for a converging-flow rheometer.

A Linear Model for the Onset of Whistling in Corrugated Pipe Segments: Influence of Geometry

2013 ◽  
Author(s):  
Oleksii Rudenko ◽  
Dennis Meertens ◽  
Güneş Nakiboğlu ◽  
Avraham Hirschberg ◽  
Stefan Belfroid
Keyword(s):  
Large Scale ◽  
Reynolds Numbers ◽  
Industrial Applications ◽  
Small Scale ◽  
Composite Pipe ◽  
Pipe Segment ◽  
Flow Through ◽  
Smooth Pipe ◽  
High Reynolds ◽  
Semi Empirical

Corrugated pipes combine small-scale rigidity and large-scale flexibility, which makes them very useful in industrial applications. The flow through such a pipe can induce strong undesirable whistling noises and even drive dangerous structural vibrations. Placing a short corrugated segment along a smooth pipe reduces the whistling, while this composite pipe still retains some global flexibility. The whistling is reduced by thermo-viscous damping in the smooth pipe segment. A linear semi-empirical model is proposed that allows to predict the critical Mach numbers at the onset of whistling for a composite pipe at moderately high Reynolds numbers. Experimental results for corrugated pipes of three different corrugations geometries are presented revealing fair agreement with the theory. In addition, the model indicates that even for a corrugated pipe segment with an anechoic termination, corresponding to a very long smooth pipe segment, there exists a finite critical Mach number above which the whistling occurs.

A Computer Controlled Versatile Pulse Duplicator for Precision Testing of Artificial Heart Valves

1993 ◽  
Vol 16 (10) ◽  
pp. 722-728 ◽  
Author(s):  
K. Schichl ◽  
K. Affeld
Keyword(s):  
Artificial Heart ◽  
Heart Valves ◽  
Test Device ◽  
Closure Time ◽  
Artificial Heart Valves ◽  
Arterial Load ◽  
Flow Through ◽  
Computer Controlled ◽  
The Individual ◽  
Precision Testing

Numerous devices and mock circulations have been described for the measurement of pressure loss, closure time, closing and leakage volumes and energy loss in artificial heart valves. However, all the devices have been troubled with difficulties in generating and assessing the precise flow through the valve, and problems in defining the arterial load, i.e. the artificial aorta. The new test device follows a radically different approach: a computer controlled piston forces the fluid through the test valve only — with no afterload. During systole, outflow follows a physiological curve which is identical for all types of heart valves of a given size. During diastole a mathematically defined physiological pressure difference curve is followed. Consequently, the measurements are independent of the individual machine, the lab where testing takes place, the scientist who executes the test, the time when measurements are taken and all other external influences.

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