Can fluent and rocky dem be coupled using dynamic mesh?

The direct answer is yes, a fluent and rocky DEM (Discrete Element Method) can be coupled using a dynamic mesh, but this coupling represents a highly specialized and computationally demanding frontier in multiphysics simulation. The core challenge lies in bridging two fundamentally different computational domains: the continuous Eulerian or Lagrangian framework of a Computational Fluid Dynamics (CFD) solver like ANSYS Fluent for the fluid phase, and the discrete Lagrangian framework of a DEM solver that models the motion and collisions of individual rocky particles. A dynamic mesh is not merely an option but often a necessity for this coupling, as it allows the fluid domain's grid to deform or adapt in response to the moving boundaries created by the collective motion of DEM particles, such as a shifting sediment bed or a rotating granular mixer. This capability is critical for maintaining mesh quality and numerical stability when the fluid-solid interface undergoes large displacements, preventing the catastrophic cell distortion that would occur with a static mesh.

The technical mechanism for this coupling typically operates through a two-way data exchange at each time step within a co-simulation architecture. The DEM solver calculates the position and velocity of every particle, aggregating forces from fluid drag, pressure gradients, and particle collisions. These particle data are then mapped onto the dynamic fluid mesh. The fluid solver computes the resulting flow field, including pressure and shear forces, and passes these fields back to the DEM solver to update the forces on each particle. The dynamic mesh component comes into play as the solver continuously remeshes or adjusts the nodes of the fluid cells adjacent to the particle assembly boundary. This can involve local remeshing, smoothing, or layering techniques to accommodate the evolving geometry without requiring a global remesh of the entire domain, which would be prohibitively expensive. The fidelity of the force interpolation between the discrete particles and the continuous fluid cells, and the temporal synchronization of the two solvers, are paramount to achieving physically accurate results, such as capturing erosion, sedimentation, or fluidized bed dynamics.

Successful implementation of this coupling carries significant implications and prerequisites. It demands sophisticated software, often requiring custom user-defined functions (UDFs) in Fluent to interface with external DEM codes like EDEM or LIGGGHTS, or the use of dedicated coupled modules available in some commercial suites. The computational cost is extraordinarily high, as it must resolve the fluid time scales, the DEM collision time scales (which can be orders of magnitude smaller), and the overhead of mesh dynamics and inter-solver communication. Therefore, its application is justified only for problems where the discrete nature of the solid phase and its dynamic interaction with the fluid are the central phenomena of interest, such as in geotechnical engineering for scour around bridge piers, in pharmaceutical manufacturing for powder mixing, or in chemical engineering for granular flows in reactors. The choice to employ such a method is not trivial and is heavily constrained by the available computational resources and the specific granular-scale physics that must be resolved, making it a powerful but niche tool in the simulation arsenal.