Computer Simulation Study of Collective Phenomena in Dense Suspensions of Red Blood Cells under Shear [recurso electrónico

The rheology of dense red blood cell suspensions is investigated via computer simulations based on the lattice Boltzmann, the immersed boundary, and the finite element methods. The red blood cells are treated as extended and deformable particles immersed in the ambient fluid. In the first part of the work, the numerical model and strategies for stress evaluation are discussed. In the second part, the behavior of the suspensions in simple shear flow is studied for different volume fractions, particle deformabilities, and shear rates. Shear thinning behavior is recovered. The existence of a shear-induced transition from a tumbling to a tank-treading motion is demonstrated. The transition can be parameterized by a single quantity, namely the effective capillary number. It is the ratio of the suspension stress and the characteristic particle membrane stress. At the transition point, a strong increase in the orientational order of the red blood cells and a significant decrease of the particle diffusivity are observed. However, the average cell deformation shows no signature of the transition. Front Matter....Pages i-xiii Front Matter....Pages 3-3 Motivation, aims, and outline of the thesis....Pages 1-2 Introduction to complex fluids and their rheology....Pages 5-10 Introduction to the physics of red blood cells and hemorheology....Pages 11-14 Front Matter....Pages 15-15 Physical considerations and ingredients for the numerical model....Pages 17-19 Fluid solver: the lattice Boltzmann method....Pages 21-36 Fluid-structure interaction: the immersed boundary method....Pages 37-42 Membrane model and energetics....Pages 43-48 Advanced model discussions....Pages 49-69 Front Matter....Pages 71-71 Stress evaluation in combined immersed boundary lattice Boltzmann simulations....Pages 73-84 Rheology and microscopic behavior of red blood cell suspensions....Pages 85-120 Conclusions and outlook....Pages 121-126 Back Matter....Pages 127-165

Complex fluids and their rheology Physics of red blood cells and hemorheology Numerical model for simulations of red blood cell suspensions Physical considerations and ingredients for the numerical model Fluid solver: the lattice Boltzmann method Fluid-structure interaction: the immersed boundary method Membrane model and energetics Stress evaluation in combined immersed boundary lattice Boltzmann simulations Rheology and microscopic behavior of red blood cell suspensions.

.