(582p) Simulation of Turbulence Effects On Red Blood Cell Trauma

Blood flow is often laminar, but in some cases like the coronary artery, the ascending aorta and in arteriovenous grafts, turbulent blood flow can occur in vivo. In near prosthetic heart devices, such as ventricular assist devices, artificial hearts, blood pumps, and artificial valves, turbulence occurs much more often [1] . Locally high shear stresses and significant pressure fluctuations are some of the negative effects of turbulence in blood. In addition, physical contact within these devices produces mechanical forces. Such flow conditions can often cause hemolysis that can be experimentally observed through hemoglobin release from erythrocytes or red blood cells, RBC, because of destruction or trauma of the RBC. Design of such devices, therefore, depends on understanding and predicting the effect of turbulent shear stresses on RBC. However, the structure and the effects of turbulence on the cells remains unclear, and application of computational fluid dynamics in conjunction with better correlations to predict blood damage could significantly improve the development of blood contacting devices.

Blood trauma is in general considered to be a function of time exposure to high stresses and of the magnitude of the shear stresses. Furthermore, recent work out of our laboratory has indicated that extensional stresses can also be detrimental to RBC [2]. Computational techniques that can predict the detailed structure of turbulence can be used to investigate the effect of turbulent eddy structures on cell damage. In this work, we use Reynolds-averaged Navier-Stokes models of turbulence (kappa-epsilon) to simulate classic Couette flow hemolysis experiments [3, 4]. The goal is to relate the hemolysis seen experimentally to the characteristics of turbulence in the flow. Reynolds stresses and Kolmogorov scales are calculated and correlated to the observed hemolysis. After discussing the validation of our simulations, we will discuss details of the flow that are not easily available experimentally, such as turbulence kinetic energy dissipation rates, but are important to RBC trauma.  An understanding of the scales and the structure of turbulence that is mostly responsible for blood trauma would lead to rapid design of heart assist devices that minimize blood damage. 

References

1.         Antiga, L. and D.A. Steinman, Rethinking Turbulence in Blood. Biorheology, 2009. 46: p. 77-81.

2.         Down, L.A., D.V. Papavassiliou, and E.A. O'Rear, Significance of Extensional Stresses to Red Blood Cell Lysis in a Shearing Flow. Annals of Biomedical Engineering, 2011. 39(6): p. 1632-1642.

3.         Kameneva, M.V., et al., Effects of Turbulent Stresses upon Mechanical Hemolysis: Experimental and Computational Analysis. ASAIO Journal, 2004. 50: p. 418-423.

4.         Sutera, S.P. and M.H. Mehrjardi, Deformation and Fragmentation of Human Red Blood Cells in Turbulent Shear Flow. Biophysical journal, 1975. 15.