Daniel A. Reasor

Determination of Critical Parameters in Platelet Margination

An investigation of margination dependence on hematocrit, platelet shape, and viscosity ratio of plasma to cytoplasm is presented. Whole blood is modeled as a suspension of deformable red blood cells (RBCs) and rigid platelets in a viscous liquid. The fluid phase is simulated using the lattice-Boltzmann method, the RBC membranes are modeled with a coarse-grained spectrin-link method, and the dynamics of rigid particles are updated using Newton’s equations of motion for axisymmetric shapes. The results emphasize that an increase in hematocrit increases the rate of margination. The viscosity ratio between the interior cytoplasm and suspending fluid can considerably alter the rate of margination. The aspect ratio of surrogate platelet particles influences the rate of margination as well. Spherical particles tend to migrate more quickly than disks. Highly viscous or rigid RBCs slow down margination.

Direct Numerical Simulation of Cellular Blood Flow Through a Model Arteriole Bifurcation

Blood is composed of a suspension of red blood cells (RBCs) suspended in plasma, and the presence of the RBCs substantially changes the flow characteristics and rheology of these suspensions. The viscosity of blood varies with the hematocrit (volume fraction of RBCs), which is a result not seen in Newtonian fluids. Additionally, RBCs are deformable, which can alter suspension dynamics. Understanding the physics in these flows requires accurately simulating the suspended phase to recover the microscale, and a subsequent analysis of the rheology to ascertain the continuum-level effects caused by the changes at the particle level. The direct numerical simulation of blood flow including RBC migration effects has the capability to resolve the Fahraeus effect of observing low hematocrit values near walls, the subsequent cell-depleted layer, and the presence of velocity profile blunting due to the distribution of RBCs.Copyright