Title: Numerical simulations of isotropic active gels

Author (Talk): Nicholas Derr, Harvard University

Abstract:

Biological systems allow for the generation of active stresses, which can lead to instability and pattern formation. These phenomena often stem from material fluxes induced by active stress, and hence many systems are described as single-phase active fluids. However, this description is not sufficient for modeling poroelastic systems such as the cytoskeleton. In this talk, we describe a generic continuum model of an incompressible, biphasic gel, consisting of a viscoelastic solid and viscous fluid phase coupled by frictional drag. Isotropic active stresses are induced by the presence of bound molecular motors, the binding/unbinding dynamics of which are described by a set of rate equations. Simulations are carried out using a custom implementation of Chorin's projection method to enforce incompressibility, and the large linear system resulting from the projection is solved at each time step using a geometric multigrid method. Solution of the full set of non-linear governing equations in this way allows for the behavior of isotropic active gels to be investigated at long times, far from equilibrium, in two and three dimensions.