2.1 The phase field model
The PF model for two-phase flow was applied to simulate biofilm
deformation under fluid flow. This two-dimensional continuum biofilm
model was implemented using COMSOL Multiphysics (COMSOL v5.4, Comsol
Inc, Burlington, MA) with finite element method. COMSOL has
computational fluid dynamics and phase field modeling as built-in
features, and we implemented the constitutive equation (i.e., Oldroyd-B
viscoelastic model) for the biofilm viscoelastic behavior using partial
differential equation (PDE) module. The biofilm was considered an
incompressible viscoelastic liquid.