  In this work we consider how surface-adherent bacterial biofilm communities
respond in flowing systems. We simulate the fluid-structure interaction and
separation process using the immersed boundary method. In these simulations we
model and simulate different density and viscosity values of the biofilm than
that of the surrounding fluid. The simulation also includes breakable springs
connecting the bacteria in the biofilm. This allows the inclusion of erosion
and detachment into the simulation. We use the incompressible Navier-Stokes
(N-S) equations to describe the motion of the flowing fluid. We discretize the
fluid equations using finite differences and use a geometric multigrid method
to solve the resulting equations at each time step. The use of multigrid is
necessary because of the dramatically different densities and viscosities
between the biofilm and the surrounding fluid. We investigate and simulate the
model in both two and three dimensions.
  Our method differs from previous attempts of using IBM for modeling
biofilm/flow interactions in the following ways: the density and viscosity of
the biofilm can differ from the surrounding fluid, and the Lagrangian node
locations correspond to experimentally measured bacterial cell locations from
3D images taken of Staphylococcus epidermidis in a biofilm.
