The dynamic mesh model in Ansys Fluent can be used to model flows where the shape of the domain is changing with time due to motion on the domain boundaries. The dynamic mesh model can be applied to single or multiphase flows (and multi-species flows). The generic transport equation (Equation 3–1) applies to all applicable model equations, such as turbulence, energy, species, phases, and so on. The dynamic mesh model can also be used for steady-state applications, when it is beneficial to move the mesh in the steady-state solver. The motion can be a prescribed motion (for example, you can specify the linear and angular velocities about the center of gravity of a solid body with time) or an unprescribed motion where the subsequent motion is determined based on the solution at the current time (for example, the linear and angular velocities are calculated from the force balance on a solid body, as is done by the six degree of freedom (six DOF) solver; see Six DOF Solver Settings in the User's Guide). The update of the volume mesh is handled automatically by Ansys Fluent at each time step based on the new positions of the boundaries. To use the dynamic mesh model, you need to provide a starting volume mesh and the description of the motion of any moving zones in the model. Ansys Fluent allows you to describe the motion using either boundary profiles, user-defined functions (UDFs), or the six degree of freedom solver.

Ansys Fluent expects the description of the motion to be specified on either face or cell zones. If the model contains moving and non-moving regions, you need to identify these regions by grouping them into their respective face or cell zones in the starting volume mesh that you generate. Furthermore, regions that are deforming due to motion on their adjacent regions must also be grouped into separate zones in the starting volume mesh. The boundary between the various regions need not be conformal. You can use the non-conformal or sliding interface capability in Ansys Fluent to connect the various zones in the final model.