Rotating zones can be used to model rotating systems such as turbines, fans, ventilators and similar systems. This chapter shows how a simulation with a rotating part can be set up on the SimScale platform.
Firstly, a cell-zone is required as part of the mesh which contains a cylindrical zone around the rotor. Find out how to create a cell zone here.
In the tree, navigate to Advanced concepts and add a rotating zone. Two types of rotating zones are supported:
Steady-state: Multi Reference Frame (MRF)
MRF is a Steady-State approximation of the transient rotating motion at an ‘instance’ of time. So, the body/mesh is not physically rotated. One must make sure that the problem does not include large-scale transient phenomena.
This approach uses a rotating frame of reference that modifies the governing equations in the rotating zone. Additional source terms that incorporate forces in the rotating reference frame are taken into account that simulate a rotation effect in the flow.
Performing MRF simulations is computationally much less demanding than transient modeling. Hence, if the problem is set up correctly, MRF provides good approximations with less computational effort and considerably less compute times.
Transient: Arbitrary Mesh Interface (AMI)
AMI simulations are fully Transient and therefore are computationally much more expensive than MRF. They take all transient effects into account and are usually sensitive to the time step length. AMI can be specified as oscillating or full rotating motion.
In the AMI approach a mesh interface is created between the moving and stationary parts of mesh. At each time step, The rotating zone is physically rotated and quantities are interpolated at this interface to allow realistic movement of the rotating parts.
The rotation is define by the following properties:
- Rotation center
- Rotation axis
- Angular velocity
Alternatively, the Rotation axis and Angular velocity could be combined into Radial velocity. The oscillating rotating motion requires an Amplitue vector instead of the Rotation axis. Once the rotation is defined, it should be assigned to the rotating zone that is created as part of the mesh.
For a practical guide on how to set up and use rotating zones, take a look at this tutorial simulating the flow in a centrifugal pump.