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Ahmed Body on 25degree

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Old   March 16, 2011, 17:16
Default Ahmed Body on 25degree
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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
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Old   March 17, 2011, 16:28
Vinicius Girardi
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In which order of magnitude it is oscilating?
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Old   March 22, 2011, 09:16
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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?

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Old   August 18, 2011, 07:35
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Girish Gaikwad
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try using trimmer mesh...
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