In the Ansys Fluent [44] Eulerian multiphase model, the fluid phase conservation equations are identical to the fluid equations of the DEM-CFD coupling presented in section Governing equations. This enabled the usage of Fluent solver in this coupling implementation with Rocky for one-way and two-way coupling modes.
Note: Constant one-way does not require the Fluent solver.
The choice of using Ansys Fluent to solve the fluid phase was mainly due to its user-defined functions support (UDFs) for the customization of some parts of the code. This feature has allowed the definition of the source terms in the fluid phase conservation equations that carried out the integration of DEM model for modeling the solid phase.
Ansys Fluent [5] solver is based on the standard finite volume method which is cell centered and adopts an implicit scheme for time stepping. A block algebraic multigrid solver is used for the solution of the linearized equations [4].
The momentum and energy equations of the phase that represents the discrete phase are not solved by Fluent, the dispersed phase velocity and temperature fields are solved by Rocky. A source term is included on the disperse phase continuity equation to impose the disperse volume fraction calculated at the DEM side. The momentum exchange term is not calculated in the CFD solver, but on the DEM side, as explained in section Governing equations, and included through a source term in the continuous phase momentum equation. The PC-SIMPLE algorithm, which is the SIMPLE algorithm extended to multiphase flows, is used for the pressure-velocity coupling. More detailed information about this coupling segregated pressure-based method can be found in the paper by Vasquez and Ivanov [3].