Discovery generally solves the equations of fluid flow and heat transfer in a stationary (or inertial) reference frame. However, there are many problems where the equations might need to be solved in a moving (or non-inertial) reference frame. For example, fans and mixing tanks with their rotating blades, impellers, and similar objects (comprising a cylindrical body and blades) cause the fluid around those parts to flow with some rotation. In most cases, the moving parts render the problem unsteady when viewed from the stationary frame. However, the flow around the moving part can (with certain restrictions) be modeled as a steady-state problem with respect to the moving frame.

In this quick tip video, we will see how you can apply rotating fluid zone in Discovery.

Refer this documentation to understand this better: Rotating Fluid Zones