Cyclic Symmetry in ANSYS Workbench

Cyclic Symmetry

Rotating equipment like turbines, propellers and fans are often symmetric and one can run simulations on parts of the structure. The method is called Cyclic Symmetry and ANSYS has excellent features to capture the correct physics of the entire structure based on the Cyclic Symmetry model.

ANSYS Workbench however currently lacks some of this functionality, but this article explains how to solve the challenge.

TUTORIAL: Cyclic Symmetry Analysis in ANSYS Workbench

If we have a cyclic symmetric structure which is supposed to have symmetric response, no special technique is needed and Frictionless Support on the symmetry planes will be enough.

However if the response is not symmetric, such as the structure in the figure 1, which has a moment as loading, we have to perform cyclic symmetry analysis in Workbench by using command objects.

Figure 1. A full model with unsymmetric loading

To perform such an analysis, first of all we have to cut a cyclic sector with its share of loading and boundary condition. In this example, a 1/6th sector is created. The Pressure is the same while The Moment is 1/6th of the full model.

Figure 2. a 1/6th sector of the full model

The second step is to insert a command objects by right-clicking Static Structural:

Figure 3. inserting a “commands” object

Now we can type 3 commands as shown in Figure 4. The CYCLIC command activates the symmetry solution technique and the parameter 6 means there is 6 sectors in the full model.

Figure 4. Commands snippet for activating cyclic solution.

We can also insert some commands under Solution for postprocessing, see Figure 5. The reason to do so is that in nowadays Workbench we cannot expand structure symmetrically in postprocessing. The commands object will create a expanded stress plot after solving the model. However the plot is static so it is important to define view point and view angle previously.

Figure 5. Commands for generating stress plot for a expanded full model.

When solving process begins, we can open Solution Information and check the CYCLIC command output.

Figure 6. The CYCLIC command output.

Now solution is completed and we can continue with postprocessing.

Figure 7. Stress plot in workbench for one sector.

Figure 8. Stress plot for the expanded full model.

Do you want to learn more?

EDR provides a training course that covers Cyclic Symmetry in more detail, as well as other interesting topics.

Or contact our ANSYS Support to ask for hints!