Laser Anemometry Measurements of Steady Flow Past Aortic Valve Prostheses

1993 ◽  
Vol 115 (3) ◽  
pp. 290-298 ◽  
Author(s):  
Y. T. Chew ◽  
H. T. Low ◽  
C. N. Lee ◽  
S. S. Kwa
Keyword(s):  
Steady Flow ◽  
Heart Valves ◽  
Flow Region ◽  
Ball Valve ◽  
Prosthetic Heart Valves ◽  
Shear Stresses ◽  
Normal Stresses ◽  
Reversed Flow ◽  
Disk Valve ◽  
Wall Shear

An experimental investigation was conducted in steady flow to examine the fluid dynamics performance of three prosthetic heart valves of 27 mm diameter: Starr-Edwards caged ball valve, Bjork-Shiley convexo-concave tilting disk valve, and St. Vincent tilting disk valve. It was found that the pressure loss across the St. Vincent valve is the least and is, in general, about 70 percent of that of the Starr-Edwards valve. The pressure recovery is completed about 4 diameters downstream. The velocity profiles for the ball valve reveal a large single reversed flow region behind the occluder while those for the tilting disks valves reveal two reversed flow regions immediately behind the occluders. Small regions of stasis are also found near the wall in the minor opening of Bjork-Shiley valve and in the major opening of St. Vincent valve. The maximum wall shear stresses of the three valves at a flow rate of 30 l/min are in the range 30–50 dyn/cm2 which can cause hemolysis of attached red blood cells. The corresponding maximum Reynolds normal stresses are in the range of 1600–3100 dyn/cm2. The Reynolds normal stresses decay quickly and return approximately to the upstream undisturbed level at about 4 diameters downstream while the wall shear stresses decay at a slower rate. The maximum Reynolds normal stresses occur at about 1 diameter downstream while the maximum wall shear stress is at about 2 diameters downstream. In general, the St. Vincent valve has better performance. A method to compensate for refractive index variations and curvature effect of the sinus region of the aorta root using laser doppler anemometer measurements is also proposed.

scholarly journals Stereoscopic PIV of Steady Flow Through a Bileaflet Mechanical Heart Valve

2008 ◽  
Author(s):  
C. Hutchison ◽  
P. E. Sullivan ◽  
C. R. Ethier
Keyword(s):  
Steady Flow ◽  
Heart Valve ◽  
Heart Valves ◽  
Mechanical Heart Valve ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Shear Stresses ◽  
Stereoscopic Piv ◽  
Bileaflet Mechanical Heart Valve ◽  
Component Particle

Each year over 180,000 mechanical heart valves are implanted worldwide, with the bileaflet mechanical heart valve (BiMHV) accounting for approximately 85% of all valve replacements [1,2]. Although much improved from previous valve designs, aortic BiMHV design is far from ideal, and serious complications such as thromboembolism and hemolysis often result. Hemolysis and platelet activation are thought to be caused by turbulent Reynolds shear stresses in the flow [1]. Numerous previous studies have examined aortic BiMHV flow using LDA and two component Particle Image Velocimetry (PIV), and have shown the flow to be complex and three-dimensional [3,4]. Stereoscopic PIV (SPIV) can obtain all three velocity components on a flow plane, and hence has the potential to provide better understanding of three dimensional flow characteristics. The objective of the current study was to use SPIV to measure steady flow, including turbulence properties, downstream of a BiMHV in a modeled aorta. The resulting dataset will be useful for CFD model validation, and the intent is to make it publicly available.

Non-Newtonian effects in steady motion of some idealized elastico-viscous liquids

1958 ◽  
Vol 245 (1241) ◽  
pp. 278-297 ◽  
Keyword(s):  
Steady Flow ◽  
Apparent Viscosity ◽  
Steady Motion ◽  
Shear Stresses ◽  
Normal Stresses ◽  
Straight Pipe ◽  
Shearing Flow ◽  
Viscous Liquids ◽  
Variable Shear ◽  
Steady Shearing

Normal-stress effects and the variation of apparent viscosity with rate of shear in simple types of steady flow of certain idealized elastico-viscous liquids are discussed. The liquids are those whose behaviour at sufficiently small variable shear stresses can be characterized by three constants (a coefficient of viscosity, a relaxation time and a retardation time) and whose invariant differential equations of state for general motion (involving eight independent physical constants) are linear in the stresses and include terms of no higher degree than the second in the stresses and velocity gradients together. The normal stresses which, in addition to shear stresses, are present in such a liquid in a state of simple shearing flow, or in flow in a circular pipe, or between rotating cylinders, are investigated; and the conditions under which the Weissenberg climbing effect will occur, in a positive or negative sense, are examined. In many liquids of this class, steady rectilinear flow under a uniform pressure gradient is not always possible in a straight pipe of arbitrary section, nor is steady flow in horizontal circles in a region bounded by arbitrary surfaces of revolution in relative rotation about common vertical axis. The behaviour of these idealized liquids when sheared in a narrow gap between a rotating wide-angled cone and a flat plate is compared with the observations of Roberts (1952, 1953) on some real elastico-viscous liquids. Certain liquids of this class, characterized by six independent constants satisfying certain inequalities, exhibit rheological behaviour which is, at least qualitatively, similar to the behaviour of many real elastico-viscous liquids in the following respects: the behaviour at small variable shear stresses, the variation of apparent viscosity with rate of steady shearing, the climbing effect up a vertical rod rotated in the liquid, and a distribution of normal stresses equivalent to an extra tension along the streamlines (with an isotropic state of stress in the plane normal to the streamlines) which is present in all the simple types of steady shearing flow investigated. These liquids can flow steadily in straight lines through a straight pipe of any section.

Evaluation of Platelet Activation Models With Dynamic Shear Stress In Vitro Experiments

2012 ◽  
Author(s):  
Jawaad Sheriff ◽  
Michalis Xenos ◽  
João S. Soares ◽  
Jolyon Jesty ◽  
Danny Bluestein
Keyword(s):  
Platelet Activation ◽  
Heart Valves ◽  
Ventricular Assist Devices ◽  
Prosthetic Heart Valves ◽  
Shear Stresses ◽  
Ventricular Assist ◽  
Relative Paucity ◽  
Valvular Diseases ◽  
End Stage

Blood recirculating devices, which include ventricular assist devices and prosthetic heart valves, are necessary for some patients suffering from end-stage heart failure and valvular diseases. However, disturbed flow patterns in these devices cause shear-induced platelet activation and aggregation. Thromboembolic complications resulting from this platelet behavior necessitates lifelong anticoagulant therapy for patients implanted with such devices. In addition, blood recirculating device manufacturers mostly test and optimize their products for hemolysis, which occurs at shear stresses ten-fold higher than required for platelet activation. The relative paucity of optimization for flow-induced thrombogenicity is further exacerbated by the fact that there are few predictive shear-induced platelet activation models.

Bleeding Complications in Treatment with ASA and Anticoagulants

1979 ◽  
Author(s):  
J. Dale ◽  
E. Myhre
Keyword(s):  
Placebo Group ◽  
Heart Valves ◽  
Ball Valve ◽  
Bleeding Complications ◽  
Prosthetic Heart Valves ◽  
Platelet Adhesiveness ◽  
High Incidence ◽  
Intracranial Complications ◽  
Bleeding Episodes ◽  
Valve Prostheses

Patients with prosthetic heart valves have a reduced platelet adhesiveness and a high incidence of arterial thromboembolic episodes. Therefore 148 patients with aortic ball valve prostheses were chosen for an antithrombotic study. They received either one gm. of ASA or placebo in combination with anticoagulants. In two years, 15 bleeding episodes developed in those taking ASA, seven during the firstmonth. Two had intracranial hemorrhage, one died, while the others recovered completely. Six episodes occurred in the placebo group, three intracranial complications caused two deaths. The higher incidence of bleeding in the combined group was entirely due to gastrointestinal hemorrhage. In both groups, the occurrence and severity of bleeding correlated to the intensity of anticoagulant therapy. Low platelet adhesiveness also predisposed to bleeding.

Laboratory Testing of Prosthetic Heart Valves

1987 ◽  
Vol 16 (2) ◽  
pp. 67-76 ◽  
Author(s):  
H Reul ◽  
M Giersiepen ◽  
E Knott
Keyword(s):  
Steady Flow ◽  
Pulsatile Flow ◽  
Laboratory Testing ◽  
Heart Valves ◽  
Fatigue Testing ◽  
Comparative Test ◽  
Prosthetic Heart Valves ◽  
Test Results ◽  
Testing Methods

A whole range of laboratory testing methods for prosthetic heart valves, such as steady flow testing, pulsatile flow testing, and fatigue testing, are presented. Comparative test results for various valve types are given and relative valve performance is discussed.

Two-Component Laser Velocimeter Measurements Downstream of Heart Valve Prostheses in Pulsatile Flow

1986 ◽  
Vol 108 (1) ◽  
pp. 59-64 ◽  
Author(s):  
W. G. Tiederman ◽  
M. J. Steinle ◽  
W. M. Phillips
Keyword(s):  
Shear Stress ◽  
Pulsatile Flow ◽  
Turbulent Shear ◽  
Prosthetic Heart Valves ◽  
Shear Stresses ◽  
Axial Distance ◽  
Prosthetic Valves ◽  
Disk Valve ◽  
Two Component ◽  
Stress Levels

Elevated turbulent shear stresses resulting from disturbed blood flow through prosthetic heart valves can cause damage to red blood cells and platelets. The purpose of this study was to measure the turbulent shear stresses occurring downstream of aortic prosthetic valves during in-vitro pulsatile flow. By matching the indices of refraction of the blood analog fluid and model aorta, correlated, simultaneous two-component laser velocimeter measurements of the axial and radial velocity components were made immediately downstream of two aortic prosthetic valves. Velocity data were ensemble averaged over 200 or more cycles for a 15-ms window opened at peak systolic flow. The systolic duration for cardiac flows of 8.4 L/min was 200 ms. Ensemble-averaged total shear stress levels of 2820 dynes/cm2 and 2070 dynes/cm2 were found downstream of a trileaflet valve and a tilting disk valve, respectively. These shear stress levels decreased with axial distance downstream much faster for the tilting disk valve than for the trileaflet valve.

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.

scholarly journals Elongational Stresses and Cells

Cells ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 2352
Author(s):  
Kylie M. Foster ◽  
Dimitrios V. Papavassiliou ◽  
Edgar A. O’Rear
Keyword(s):  
Heart Valves ◽  
Cell Injury ◽  
Extensional Flow ◽  
Cross Flow ◽  
Food Product ◽  
Artificial Organs ◽  
Microfluidic Channels ◽  
Prosthetic Heart Valves ◽  
Shear Stresses ◽  
Cell Deformability

Fluid forces and their effects on cells have been researched for quite some time, especially in the realm of biology and medicine. Shear forces have been the primary emphasis, often attributed as being the main source of cell deformation/damage in devices like prosthetic heart valves and artificial organs. Less well understood and studied are extensional stresses which are often found in such devices, in bioreactors, and in normal blood circulation. Several microfluidic channels utilizing hyperbolic, abrupt, or tapered constrictions and cross-flow geometries, have been used to isolate the effects of extensional flow. Under such flow cell deformations, erythrocytes, leukocytes, and a variety of other cell types have been examined. Results suggest that extensional stresses cause larger deformation than shear stresses of the same magnitude. This has further implications in assessing cell injury from mechanical forces in artificial organs and bioreactors. The cells’ greater sensitivity to extensional stress has found utility in mechanophenotyping devices, which have been successfully used to identify pathologies that affect cell deformability. Further application outside of biology includes disrupting cells for increased food product stability and harvesting macromolecules for biofuel. The effects of extensional stresses on cells remains an area meriting further study.

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.

scholarly journals ADP and Retention of Platelets in Glass Bead Columns

1977 ◽  
Author(s):  
J. Dale
Keyword(s):  
Whole Blood ◽  
Glass Bead ◽  
Heart Valves ◽  
Adenine Nucleotides ◽  
Ball Valve ◽  
Red Cells ◽  
Prosthetic Heart Valves ◽  
Modified Method ◽  
Edta Blood ◽  
Edta Anticoagulated Blood

Platelet retention is known to be dependent upon ADP, thought to be derived either from red cells by hemolysis in the glass bead columns or from the platelets themselves. In order to study this, the following experiments were done in blood from 8 healthy subjects and 11 patients with prosthetic heart valves: The whole blood content of adenine nucleotides was measured, the platelet retention in whole blood was determined by Hellem’s modified method, the degree of hemolysis provoked by passage of whole blood and EDTA-anticoagulated blood was estimated, and finally the liberation of adenine, nucleotides from EDTA-blood was measured. The wholeblood content of ADP was similar in the two groups of subjects, as was the degree of hemolysis caused by passage of blood through the columns, while platelet retention was low in blood from the ball-valve patients. The adenine nucleotides were liberated in the same proportions as hemoglobin, and ADP appeared in plasma in mean concentrations of 0.10 juM in both groups of subjects after passage of EDTA-blood through the columns. The results indicate that ADP in amounts necessary to induce platelet retention is derived from red cells. The reduced retention in ball-valve patients in spite of normal ADP-liberation is probably a result of trauma to the platelets inflicted by the prosthetic valve.

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