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# Simulation of a 90° section of a 360° radial compressor with Periodic Boundary Condition

Hello Everybody

I am simulating the flow in a radial compressor and had the idea to save calculation time by spliting the part into 4 90° sections through the middle of the flow chambers (12 Blades for this test). I want to use the "Periodic Boundary Condition- rotational" tool to connect the open walls of the sections but i always get an error because the "dependend mesh" tool gets overwritten by the Fluid Domain so that the meshes are not simmilar anymore, which is mandatory for the "Periodic Boundary Condition- rotational" tool.

1. Do you think it is a good idea at all to split the compressor rotational?

2. Do you know an other way to solve the problem?

Thank you very much

kind regards

Solution
Solution
Accepted by topic author DanielOn
‎08-26-2015 04:32 AM

## Re: Simulation of a 90° section of a 360° radial compressor with Periodic Boundary Condition

Daniel,

The two periodic faces that represent the common boundaries of the periodic flow must have identical meshes. With the fluid domain/Fluid surface mesh BC, it is hard to respect this condition in some models (some corner nodes) even with match solid mesh option in the FS mesh. As a workaround, please place the attached meshMatching.dat file in the same directory as the sim file. Edit the file; here is a description:

Here is a description (ie Periodic BC (1)):

1-      Tag: the name of the periodic BC.

2-      0.0 0.0 0.0 - Trans_x,y,z: this is the translation value you want to apply from one face to the other (in global coordinates). In your case, it should be zero, since you only need rotation.

3-      Axis_x,y,z: this is the axis of rotation you want to use from one face to the other (in global coordinates). In your case, it is Z, so I entered (0 0 1).

4-      Center_x,y,z: this is the center point for the axis of rotation (in global coordinates). In your case, it is the origin of the global system, so I entered (0 0 0).

5-      Theta: is the rotation angle in degrees from face 1 to 2. You can enter positive or negative numbers.

The fluid domain mesher will read this file and impose identical meshes for the boundaries of the periodic flow.

Phil

Philippe Tremblay
phillippe.tremblay.ext@siemens.com
www.mayahtt.com