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How To Choose Between Rotating Zone and Rotating Wall?

This article describes how to choose between a rotating zone and a rotating wall by discussing different scenarios.

The following chart gives an overview over the current possible options to simulate motion in SimScale:

boundary condition for motion schematic
Figure 1: Options for motion in SimScale

Wall Boundary Condition

Under the Boundary conditions > Wall, you can choose between different options, such as moving wall and rotating wall.

wall boundary condition settings
Figure 2: Assigning a Wall boundary condition in SimScale. Choose between Moving wall or Rotating wall.

A) Moving Wall

Moving wall can be applied for flat surfaces which has a movement that translates. You would choose this, for e.g. when you want to simulate a vehicle driving on a street:

moving wall application on a street simscale
Figure 3: Moving wall boundary condition

B) Rotating Wall

Rotating walls can be applied to cylindrical surfaces which rotate:

rotating wall application simscale
Figure 4: Rotating wall boundary condition

This is only valid for cylindrical surfaces. Read more about other types of wall boundary conditions with an example here.

Rotating Zone

Rotating zones can be found under Advanced concepts. Here you can choose between AMI and MRF. For transient simulations, you need to select AMI and for steady-state MRF. This document provides a more technical background regarding rotating zones.

rotating zones in simscale workbench
Figure 5: Find Rotating zones in the simulation tree under Advanced concepts.

C) MRF

The Multiple Reference Frame (MRF) rotating zone is a steady-state approximation of the transient rotating motion at an “instance” of time. Therefore, the mesh/body is not physically rotated. One must make sure that the problem does not include large-scale transient phenomena.

You select MRF if you have a geometry, that is not symmetric. Here you will have a rotation for the whole mesh inside the rotating zone.

rotating zone covering everything that is supposed to rotate
Figure 6: Rotating zone covering everything that is supposed to rotate

You normally need a rotating zone for simulating pumps, turbines or fans.

D) AMI

Arbitrary Mesh Interface (AMI) rotating zone 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.

Note

If none of the above suggestions solved your problem, then please post the issue on our forum or contact us.

Last updated: January 21st, 2021

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