Turbulence Characteristics Downstream of Bileaflet Aortic Valve Prostheses

1999 ◽  
Vol 122 (2) ◽  
pp. 118-124 ◽  
Author(s):  
J. S. Liu ◽  
P. C. Lu ◽  
S. H. Chu
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Cell Damage ◽  
Reliable Estimate ◽  
In Vitro Tests ◽  
Shear Stresses ◽  
Reynolds Stresses ◽  
Aortic Sinus ◽  
Mean Velocity ◽  
Jude Medical

This study was focused on a series of in vitro tests on the turbulent flow characteristics of three bileaflet aortic valves: St. Jude Medical (SJM), CarboMedics (CM), and Edwards Tekna (modified Duromedics, DM). The flow fields of the valves were measured in a pulsatile flow model with a laser-Doppler anemometer (LDA) at the aortic sinus area downstream of the valves. The heart rate was set at 70 beats per minute, the cardiac output was maintained at 5 liters per minute, and the aortic pressure wave forms were kept within the physiological range. Cycle-resolved analysis was applied to obtain turbulence data, including mean velocity, Reynolds stresses, autocorrelation coefficients, energy spectral density functions, and turbulence scales. The Reynolds shear stresses of all three valves induced only minor damage to red blood cells, but directly damaged the platelets, increasing the possibility of thrombosis. The smallest turbulence length scale, which offers a more reliable estimate of the effects of turbulence on blood cell damage, was three times the size of red blood cells and five times the size of platelets. This suggests that there is more direct interaction with the blood cells, thus causing more damage. [S0148-0731(00)00302-2]

Multiscale Modeling of Flow Induced Thrombogenicity Using Dissipative Particle Dynamics and Molecular Dynamics

2013 ◽  
Author(s):  
Danny Bluestein ◽  
João S. Soares ◽  
Peng Zhang ◽  
Chao Gao ◽  
Seetha Pothapragada ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Blood Flow ◽  
Red Blood Cells ◽  
Platelet Activation ◽  
Blood Cells ◽  
Dissipative Particle Dynamics ◽  
Particle Dynamics ◽  
Coagulation Cascade ◽  
Shear Stresses ◽  
Activated Platelets

The coagulation cascade of blood may be initiated by flow induced platelet activation, which prompts clot formation in prosthetic cardiovascular devices and arterial disease processes. While platelet activation may be induced by biochemical agonists, shear stresses arising from pathological flow patterns enhance the propensity of platelets to activate and initiate the intrinsic pathway of coagulation, leading to thrombosis. Upon activation platelets undergo complex biochemical and morphological changes: organelles are centralized, membrane glycoproteins undergo conformational changes, and adhesive pseudopods are extended. Activated platelets polymerize fibrinogen into a fibrin network that enmeshes red blood cells. Activated platelets also cross-talk and aggregate to form thrombi. Current numerical simulations to model this complex process mostly treat blood as a continuum and solve the Navier-Stokes equations governing blood flow, coupled with diffusion-convection-reaction equations. It requires various complex constitutive relations or simplifying assumptions, and is limited to μm level scales. However, molecular mechanisms governing platelet shape change upon activation and their effect on rheological properties can be in the nm level scales. To address this challenge, a multiscale approach which departs from continuum approaches, may offer an effective means to bridge the gap between macroscopic flow and cellular scales. Molecular dynamics (MD) and dissipative particle dynamics (DPD) methods have been employed in recent years to simulate complex processes at the molecular scales, and various viscous fluids at low-to-high Reynolds numbers at mesoscopic scales. Such particle methods possess important properties at the mesoscopic scale: complex fluids with heterogeneous particles can be modeled, allowing the simulation of processes which are otherwise very difficult to solve by continuum approaches. It is becoming a powerful tool for simulating complex blood flow, red blood cells interactions, and platelet-mediated thrombosis involving platelet activation, aggregation, and adhesion.

Susceptibility of density-fractionated erythrocytes to subhaemolytic mechanical shear stress

2018 ◽  
Vol 42 (3) ◽  
pp. 151-157 ◽  
Author(s):  
Antony P McNamee ◽  
Kieran Richardson ◽  
Jarod Horobin ◽  
Lennart Kuck ◽  
Michael J Simmonds
Keyword(s):  
Blood Cell ◽  
Red Blood Cells ◽  
Red Blood Cell ◽  
Blood Cells ◽  
Shear Stresses ◽  
Mechanical Stimuli ◽  
Cell Deformability ◽  
Red Blood Cell Deformability ◽  
Cell Age ◽  
Low Shear

Introduction: Accumulating evidence demonstrates that subhaemolytic mechanical stresses, typical of circulatory support, induce physical and biochemical changes to red blood cells. It remains unclear, however, whether cell age affects susceptibility to these mechanical forces. This study thus examined the sensitivity of density-fractionated red blood cells to sublethal mechanical stresses. Methods: Red blood cells were isolated and washed twice, with the least and most dense fractions being obtained following centrifugation (1500 g × 5 min). Red blood cell deformability was determined across an osmotic gradient and a range of shear stresses (0.3–50 Pa). Cell deformability was also quantified before and after 300 s exposure to shear stresses known to decrease (64 Pa) or increase (10 Pa) red blood cell deformability. The time course of accumulated sublethal damage that occurred during exposure to 64 Pa was also examined. Results: Dense red blood cells exhibited decreased capacity to deform when compared with less dense cells. Cellular response to mechanical stimuli was similar in trend for all red blood cells, independent of density; however, the magnitude of impairment in cell deformability was exacerbated in dense cells. Moreover, the rate of impairment in cellular deformability, induced by 64 Pa, was more rapid for dense cells. Relative improvement in red blood cell deformability, due to low-shear conditioning (10 Pa), was consistent for both cell populations. Conclusion: Red blood cell populations respond differently to mechanical stimuli: older (more dense) cells are highly susceptible to sublethal mechanical trauma, while cell age (density) does not appear to alter the magnitude of improved cell deformability following low-shear conditioning.

Eulerian-Eulerian Multiphase Modeling of Blood Cells Segregation in Flow Through Microtubes

2017 ◽  
Author(s):  
Yertay Mendygarin ◽  
Luis R. Rojas-Solórzano ◽  
Nurassyl Kussaiyn ◽  
Rakhim Supiyev ◽  
Mansur Zhussupbekov
Keyword(s):  
Shear Stress ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Heart Diseases ◽  
Accurate Determination ◽  
Shear Stresses ◽  
High Shear ◽  
Blood Damage ◽  
Solid Phases

Cardiovascular Diseases, the common name for various Heart Diseases, are responsible for nearly 17.3 million deaths annually and remain the leading global cause of death in the world. It is estimated that this number will grow to more than 23.6 million by 2030, with almost 80% of all cases taking place in low and middle income countries. Surgical treatment of these diseases involves the use of blood-wetted devices, whose relatively recent development has given rise to numerous possibilities for design improvements. However, blood can be damaged when flowing through these devices due to the lack of biocompatibility of surrounding walls, thermal and osmotic effects and most prominently, due to the excessive exposure of blood cells to shear stress for prolonged periods of time. This extended exposure may lead to a rupture of membrane of red blood cells, resulting in a release of hemoglobin into the blood plasma, in a process called hemolysis. Moreover, exposure of platelets to high shear stresses can increase the likelihood of thrombosis. Therefore, regions of high shear stress and residence time of blood cells must be considered thoroughly during the design of blood-contacting devices. Though laboratory tests are vital for design improvements, in-vitro experiments have proven to be costly, time-intensive and ethically controversial. On the other hand, simulating blood behavior using Computational Fluid Dynamics (CFD) is considered to be an inexpensive and promising tool to help predicting blood damage in complex flows. Nevertheless, current state-of-the-art CFD models of blood flow to predict hemolysis are still far from being fully reliable and accurate for design purposes. Previous work have demonstrated that prediction of hemolysis can be dramatically improved when using a multiphase (i.e., phases are plasma, red blood cells and platelets) model of the blood instead of assuming the blood as a homogeneous mixture. Nonetheless, the accurate determination of how the cells segregate becomes the critical issue in reaching a truthful prediction of blood damage. Therefore, the attempt of this study is to develop and validate a numerical model based on Granular Kinetic Theory (GKT) for solid phases (i.e., cells treated as particles) that provides an improved prediction of blood cells segregation within the flow in a microtube. Simulations were based on finite volume method using Eulerian-Eulerian modeling for treatment of three-phase (liquid-red blood cells and platelets) flow including the GKT to deal with viscous properties of the solid phases. GKT proved to be a good model to predict particle concentration and pressure drop by taking into account the contribution of collisional, kinetic and frictional effects in the stress tensor of the segregated solid phases. Preliminary results show that the improved segregated model leads to a better prediction of spatial distribution of blood cells. Simulations were performed using ANSYS FLUENT platform.

Adhesive Characteristics of Hemoglobin SC Red Blood Cells.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3780-3780
Author(s):  
Ai C. Chien ◽  
Rahima Zennadi ◽  
Laura M. De Castro ◽  
Marilyn J. Telen
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Matrix Protein ◽  
Physiological Stress ◽  
Flow Chamber ◽  
Extracellular Matrix Protein ◽  
Shear Stresses ◽  
Αvβ3 Integrin ◽  
Adhesive Properties ◽  
Hb S

Abstract Hemoglobin (Hb)-S containing red blood cells (RBCs) adhere abnormally to the vascular wall; this phenomenon is postulated to contribute to vaso-occlusive crisis and serious tissue damage. Patients homozygous for Hb S experience the most severe form of SCD, whereas heterozygous patients carrying Hb S and another hemoglobin variant, Hb C, experience somewhat milder clinical courses. Laminin is the extracellular matrix protein to which SS RBCs bind most avidly and is the ligand for the BCAM/Lu receptor. αvβ3 integrin is one of the major integrins on endothelial cells (ECs) and is the counter-receptor for LW on SS RBCs. Epinephrine activates both LW and BCAM/Lu on SS RBCs and thereby induces increased SS RBC adhesion to both ECs and laminin via a cAMP-dependent pathway. We have now compared the adhesive properties of Hb SC RBCs to SS RBCs. We measured the expression of RBC adhesion receptors, BCAM/Lu and LW, and assayed adhesion of SC RBCs to laminin and ECs (with and without prior stimulation of RBCs by epinephrine). Blood samples from Hb SC and SS patients in steady state and from normal controls (Hb AA) were collected into citrate tubes and were washed to remove plasma and buffy coat before use. The levels of BCAM/Lu and LW expression on RBCs were measured by flow cytometry using monoclonal antibodies to BCAM/Lu and anti-LW. SC RBCs expressed higher levels of BCAM/Lu (MFI 476.2, n=13) than did SS RBCs (MFI 332.3, n=33) and AA RBCs (MFI=225.5, n=16), but none of these differences were statistically significant (all p values >0.05). The levels of LW expression were also similar on AA, SC, and SS RBCs. Adhesion to laminin and ECs was measured as previously described, in a graduated height flow chamber. Non-treated, sham-treated, and epinephrine-treated RBCs were each infused into a flow chamber fitted with a slide coated with laminin or ECs. After washing at a constant rate, adherent RBCs were quantitated at points of different shear stresses. Adhesion of SC RBCs to laminin (mean of 53.1 cells/mm2 at 1 dyne/cm2, n=9) was lower than that of SS RBCs (mean of 69.0 cells/mm2 at 1 dyne/cm2, n=6, p=0.459) but was markedly higher than the adhesion seen with AA RBCs (mean of 0.03 cells/mm2 at 1 dyne/cm2, n=3, SC vs AA p=0.011). A positive correlation was found between BCAM/Lu expression and SC RBC adhesion to laminin (r=0.638, p=0.047). While epinephrine induced an increase in SC RBC adhesion to laminin in only 10% of all SC patient samples tested (compared to 50% of SS patients), epinephrine upregulated SC RBC adhesion to ECs approximately 10-fold in all samples tested (n=3). We conclude that SC RBCs represent an intermediate adhesive phenotype compared to AA and SS RBCs. While BCAM/Lu-mediated adhesion to laminin was lower on SC RBCs than on SS RBCs, unstimulated BCAM/Lu adhesive function was strikingly enhanced in relation to AA RBCs. Most importantly, epinephrine uniformly increased SC RBC adhesion to ECs, suggesting that in Hb SC disease, physiological stress may induce SC RBC adhesion and vaso-occlusive crises by mechanisms similar to those postulated to occur as a result of stress in Hb SS disease.

Hot-Wire Measurements Inside a Centrifugal Fan Impeller

1989 ◽  
Vol 111 (4) ◽  
pp. 363-368 ◽  
Author(s):  
A. Kjo¨rk ◽  
L. Lo¨fdahl
Keyword(s):  
Suction Side ◽  
Design Flow ◽  
Shear Stresses ◽  
Centrifugal Fan ◽  
Reynolds Stresses ◽  
Low Velocity ◽  
Mean Velocity ◽  
Attached Flow ◽  
The Mean ◽  
Velocity Region

Measurements of the three mean velocity components and five of the Reynolds stresses have been carried out in the blade passage of a centrifugal fan impeller. The impeller was of ordinary design, with nine backward curved blades, and all measurements were carried out at the design flow rate. The mean velocity measurements show that the flow can be characterized as an attached flow with almost linearly distributed velocity profiles. However, in a region near the suction side close to the shroud a low velocity region is created. From the turbulence measurements it can be concluded that relatively low values of the turbulent stresses are predominating in the center region of the channel. Closer to the walls higher values of the normal as well as shear stresses are noted.

Added stresses because of the presence of FENE-P bead–spring chains in a random velocity field

1997 ◽  
Vol 337 ◽  
pp. 67-101 ◽  
Author(s):  
HESHMAT MASSAH ◽  
THOMAS J. HANRATTY
Keyword(s):  
Shear Stress ◽  
Velocity Field ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Velocity Gradient ◽  
Gradient Field ◽  
Shear Stresses ◽  
Reynolds Stresses ◽  
Mean Velocity ◽  
Random Velocity

FENE-P bead–spring chains unravel in the presence of large enough velocity gradients. In a turbulent flow, this can result in intermittent added stresses and exchanges of energy between the chains and the fluid, whose magnitudes depend on the degree of unravelling and on the orientations of the bead–spring chains. These effects are studied by calculating the average behaviour at different times of an ensemble of chains, contained in a fluid particle that is moving around in a random velocity field obtained from direct numerical simulation of turbulent flow of a Newtonian fluid in a channel. The results are used to evaluate theoretical explanations of drag reduction observed in very dilute solutions of polymers.In regions of the flow in which the energy exchange with the fluid is positive, the possibility arises that turbulence can be produced by mechanisms other than the interaction of Reynolds stresses and the mean velocity gradient field. Of particular interest, from the viewpoint of understanding polymer drag reduction, is the finding that the exchange is negative in velocity fields representative of the wall vortices that are large producers of turbulence. One can, therefore, postulate that polymers cause drag reduction by selectively changing the structures of eddies that produce Reynolds stresses. The intermittent appearance of large added shear stresses is consistent with the experimental finding of a stress deficit, whereby the total local shear stress is greater than the sum of the Reynolds stress and the time-averaged shear stress calculated from the time-averaged velocity gradient and the viscosity of the solvent.

scholarly journals Dynamics of Individual Red Blood Cells Under Shear Flow: A Way to Discriminate Deformability Alterations

2022 ◽  
Vol 12 ◽  
Author(s):  
Scott Atwell ◽  
Catherine Badens ◽  
Anne Charrier ◽  
Emmanuèle Helfer ◽  
Annie Viallat
Keyword(s):  
Shear Stress ◽  
Shear Flow ◽  
Red Blood Cells ◽  
Sickle Cell ◽  
Blood Cells ◽  
Center Of Mass ◽  
Shear Plane ◽  
Shear Stresses ◽  
Cell Axis ◽  
Lower Shear

In this work, we compared the dynamics of motion in a linear shear flow of individual red blood cells (RBCs) from healthy and pathological donors (Sickle Cell Disease (SCD) or Sickle Cell-β-thalassemia) and of low and high densities, in a suspending medium of higher viscosity. In these conditions, at lower shear rates, biconcave discocyte-shaped RBCs present an unsteady flip-flopping motion, where the cell axis of symmetry rotates in the shear plane, rocking to and fro between an orbital angle ±ϕ observed when the cell is on its edge. We show that the evolution of ϕ depends solely on RBC density for healthy RBCs, with denser RBCs displaying lower ϕ values than the lighter ones. Typically, at a shear stress of 0.08 Pa, ϕ has values of 82 and 72° for RBCs with average densities of 1.097 and 1.115, respectively. Surprisingly, we show that SCD RBCs display the same ϕ-evolution as healthy RBCs of same density, showing that the flip-flopping behavior is unaffected by the SCD pathology. When the shear stress is increased further (above 0.1 Pa), healthy RBCs start going through a transition to a fluid-like motion, called tank-treading, where the RBC has a quasi-constant orientation relatively to the flow and the membrane rotates around the center of mass of the cell. This transition occurs at higher shear stresses (above 0.2 Pa) for denser cells. This shift toward higher stresses is even more remarkable in the case of SCD RBCs, showing that the transition to the tank-treading regime is highly dependent on the SCD pathology. Indeed, at a shear stress of 0.2 Pa, for RBCs with a density of 1.097, 100% of healthy RBCs have transited to the tank-treading regime vs. less than 50% SCD RBCs. We correlate the observed differences in dynamics to the alterations of RBC mechanical properties with regard to density and SCD pathology reported in the literature. Our results suggest that it might be possible to develop simple non-invasive assays for diagnosis purpose based on the RBC motion in shear flow and relying on this millifluidic approach.

A New Automatic Instrument to Investigate the Rheological Behaviour of Red Blood Cells

1979 ◽  
Author(s):  
P Teitel ◽  
K Mussler
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Isotonic Saline ◽  
Rheological Behaviour ◽  
Cylindrical Sample ◽  
Flow Behaviour ◽  
Digital Data ◽  
Shear Stresses ◽  
Automatic Instrument ◽  
Packed Red Blood Cells

Based on the principles already described (Blood Cells, 1977, 3, 55) a completely automatic instrument has been constructed for the investigation of the flow behaviour of packed red blood cells at low shear stresses (below 1 Pa). Functioning as a simple polymicroviscometer the instrument features : (1) four cylindrical sample holders with filter mountings, (2) four opto-electronic level measuring devices, (3) a microprocessor controlling the functions of the whole instrument (including the successive scan of the samples in discrete steps), (4) a digital display of the actual sample level in each holder, (5) a memory unit to store the scanning results and (6) a logarithmic chip. At the end of the investigation the data stored can be retrieved either in analog or in digital form. The analog retrieval over a potentiometric recorder generates a "filtration curve" on which the type of flow behaviour (Newtonian or more or less non-Newtonian) can be directly visualized. The digital data retrieved over a printer can be fed into a computer to calculate the equation of the flow curve. The instrument can provide information either on the forces of aggregation between individual erythrocytes or on their rigidity (washed RBC packed in buffered isotonic saline containing 1 % human albumin). These information might help illuminate the contribution of RBC rheological factors in the pathogenesis of vascular occlusion.

Measurement by PIV of Synoptic Strain Rate Downstream of a St. Jude Prosthetic Valve

1999 ◽  
Author(s):  
L. M. Lourenco ◽  
K. J. Spellings
Keyword(s):  
Blood Cells ◽  
Cell Walls ◽  
Prosthetic Valve ◽  
Thrombus Formation ◽  
Turbulent Shear ◽  
Shear Stresses ◽  
Major Contributor ◽  
Reynolds Stresses ◽  
Flowing Blood ◽  
Biochemical Signals

Abstract It is widely accepted that shear stresses in flowing blood affect the behavior of blood cells. Effects may range from the alteration of the surface properties of platelets to damage of cell walls. These effects result in the release of biochemical signals leading to platelet aggregation and thrombus formation. While numerous studies support these observations it is still unclear what the main shear mechanisms are. However, there is large support to the notion that turbulent shear stresses (Reynolds stresses) are the major contributor to the shear experienced by blood solids.

scholarly journals Dynamic deformability of sickle red blood cells in microphysiological flow

TECHNOLOGY ◽  
2016 ◽  
Vol 04 (02) ◽  
pp. 71-79 ◽  
Author(s):  
Y. Alapan ◽  
Y. Matsuyama ◽  
J. A. Little ◽  
U. A. Gurkan
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Shear Stresses ◽  
Flow Shear ◽  
Vessel Occlusion ◽  
Blood Samples ◽  
Dependent Change ◽  
A Cell ◽  
Time Dependent Change ◽  
Flow Shear Stress

In sickle cell disease (SCD), hemoglobin molecules polymerize intracellularly and lead to a cascade of events resulting in decreased deformability and increased adhesion of red blood cells (RBCs). Decreased deformability and increased adhesion of sickle RBCs lead to blood vessel occlusion (vaso-occlusion) in SCD patients. Here, we present a microfluidic approach integrated with a cell dimensioning algorithm to analyze dynamic deformability of adhered RBC at the single-cell level in controlled microphysiological flow. We measured and compared dynamic deformability and adhesion of healthy hemoglobin A (HbA) and homozygous sickle hemoglobin (HbS) containing RBCs in blood samples obtained from 24 subjects. We introduce a new parameter to assess deformability of RBCs: the dynamic deformability index (DDI), which is defined as the time-dependent change of the cell's aspect ratio in response to fluid flow shear stress. Our results show that DDI of HbS-containing RBCs were significantly lower compared to that of HbA-containing RBCs. Moreover, we observed subpopulations of HbS containing RBCs in terms of their dynamic deformability characteristics: deformable and non-deformable RBCs. Then, we tested blood samples from SCD patients and analyzed RBC adhesion and deformability at physiological and above physiological flow shear stresses. We observed significantly greater number of adhered non-deformable sickle RBCs than deformable sickle RBCs at flow shear stresses well above the physiological range, suggesting an interplay between dynamic deformability and increased adhesion of RBCs in vaso-occlusive events.

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