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-   -   Cold flow analysis on a AC generator (http://www.cfd-online.com/Forums/cfx/99560-cold-flow-analysis-ac-generator.html)

sainath.s@tdps.co.in April 6, 2012 05:49

Cold flow analysis on a AC generator
 
I am trying to run a cold flow analysis on an A.C. Generator. The set up consists of both rotating and stationary bodies.

There is a rotor and a fan on the same axis and the direction of rotation is the same. Surrounding the rotor is a stator. All these components are placed inside a box open at the top. On the top of the box is another box to represent a cooler, but for this case there are no tubes and just a dummy box on top.

My aim is to determine the pressure drop inside the generator. The fan is a radial bi-directional fan rotating at a rpm of 1800. Both the rotor and fan are shaft mounted.

I have meshed the problem(5 million elements) and set up the problem. Only input from my side is the rpm and i have set a SST model for turbulence.

When i run it (in parallel), my solution diverges.

Is there any suggestions or steps that i need to take in order to help my solution converge.

kambireddy April 6, 2012 06:55

Check your mesh quality ?

sainath.s@tdps.co.in April 6, 2012 07:02

Re:
 
My mesh stats is as below.


+--------------------------------------------------------------------+
| Mesh Statistics |
+--------------------------------------------------------------------+
| Domain Name | Orthog. Angle | Exp. Factor | Aspect Ratio |
+----------------------+---------------+--------------+--------------+
| | Minimum [deg] | Maximum | Maximum |
+----------------------+---------------+--------------+--------------+
| Cooler | 81.6 OK | 1 OK | 1 OK |
| Fan | 21.1 ok | 7 ok | 14 OK |
| Frame | 15.2 ! | 36 ! | 26 OK |
| Rotor | 7.7 ! | 106 ! | 32 OK |
| Stator | 5.1 ! | 85 ! | 54 OK |
| Global | 5.1 ! | 106 ! | 54 OK |
+----------------------+---------------+--------------+--------------+
| | %! %ok %OK | %! %ok %OK | %! %ok %OK |
+----------------------+---------------+--------------+--------------+
| Cooler | 0 0 100 | 0 0 100 | 0 0 100 |
| Fan | 0 1 99 | 0 <1 100 | 0 0 100 |
| Frame | <1 1 99 | <1 <1 100 | 0 0 100 |
| Rotor | <1 3 97 | <1 1 99 | 0 0 100 |
| Stator | <1 5 95 | <1 1 99 | 0 0 100 |
| Global | <1 2 98 | <1 <1 100 | 0 0 100 |
+----------------------+---------------+--------------+--------------+

Is there something wrong?

Far April 6, 2012 07:06

Angles are not good.

kambireddy April 6, 2012 07:11

Mesh quality check
Orthog. Angle >20 deg
Max Exp Factor < 20

Please go through the documentation to know the importance of above parameters on solution


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