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-   -   Ahmed Body on 25degree (http://www.cfd-online.com/Forums/star-ccm/86204-ahmed-body-25degree.html)

dimsum March 16, 2011 17:16

Ahmed Body on 25degree
 
Hello everyone,

I am an undergraduate who is doing a ahmed body with 25degree. This is the first time that I use a CFD software.

I have a question about the residual plot when you start running the report.
The Tdr line starts going up and down when iteration start from about 150+. May I ask is there any problem to do with the model or mesh?

Here is my setting:
inlet velocity: 40m/s
turbulence intensity: 0.5%
surface mesh: polyhedral mesher, prism layer mesher and surface remesher
physics: constant density, gas, k-epsilon turbulence, realizable k-epsilon two layer, reyonlds-average navier stokes, segregated flow, steady, three dimensional, turbulent and two layer all y+ treatment.

where the base size of the mesh is 100mm and mesh in the body is min: 1mm and target: 5mm. The floor and the wall is in slip condition. There are 4 prism layers around the body which is 1mm thick, growth rate: 1.2

Please help me out. Thanks

Vinicius March 17, 2011 16:28

In which order of magnitude it is oscilating?

abdul099 March 22, 2011 09:16

I expect the flow to seperate from the body, producing some vortices behind the body. That may be a reason for the osscillation, as you are running this case in steady state.
What are the other residuals looking like? And the forces on the body?

Cheers

girishg August 18, 2011 06:35

try using trimmer mesh...


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