Evaluation of the finite element lattice Boltzmann method for binary fluid flows

In contrast to the commonly used lattice Boltzmann method, off-lattice Boltzmann methods decouple the velocity discretization from the underlying spatial grid thereby potentially increasing the geometric flexibility of the method. The current work combines characteristic-based integration of the streaming step with the free-energy based multiphase model by Lee and Lin (2005). This allows for simulation time steps more than an order of magnitude larger than the relaxation time. Unlike previous work by Wardle and Lee (2013) that integrated intermolecular forcing terms in the advection term, the current scheme applies collision and forcing terms locally for a simpler finite element formulation. A series of thorough benchmark studies reveal that this does not compromise stability and that the scheme is able to accurately simulate flows at large density and viscosity contrasts.