When   Monday, February 9, 2009   Time   4:00 PM - 5:00 PM  
Where   Technological Instit M416 2145 Sheridan Rd.   map it
Audience   - Faculty/Staff - Student - Public
Contact   Molly E Scanlon   +1 847 491 5586  
Group   McCormick-Colloquia Engineering Sciences and Applied Mathematics

Applied Math Colloquium

Title: Complex dynamics of red blood cells and vesicles in viscous flows

Speaker: Petia Vlahovska, Dartmouth College

Abstract:

Red blood cells (RBCs) in steady shear flow can tank-tread, tumble, or "swing" (tank-treading accompanied by oscillations in the inclination angle). I will present a model that quantitatively describes this behavior. The analysis accounts for the fact that the membrane is deformable, incompressible, and resistant to bending and shearing. Considering a nearly spherical shape, I obtain analytical solutions for the creeping-flow equations via a regular perturbation expansion in the excess area.

In steady shear flows, the theory shows that a closed lipid membrane (vesicle or RBC) deforms into a prolate ellipsoid, which tumbles at low shear rates, and swings at higher shear rates. The amplitude of the oscillations decreases with shear rate. In quadratic flows, the theory predicts a peculiar coexistence of parachute- and bullet-like vesicle shapes at the flow centerline. Vesicles and RBCs always migrate towards the flow centerline unlike drops, whose direction of migration depends on the viscosity ratio. In time-dependent flows, vesicles can exhibit chaotic dynamics.

These results improve understanding of blood rheology in the microcirculation, and the mechanics of blood disorders.