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Old   August 21, 2003, 07:42
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prasat
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I have few questions and i am beginner in Fluent. Do we have moving wall boundary conditions in fluent or gambit.? What is underrelaxation factor mean? pressure 0.3 density 1.0 Body forces 1.0 Momentum 0.7

prasat
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Old   August 21, 2003, 08:37
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ap
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Yes, you can activate the moving wall function directly in FLUENT, using the Boundary Condition panel.

If not all your walls are moving, I suggest to give to the moving wall a different name in GAMBIT: this will help you to find the right wall in the boundary condition panel.

Under-relaxation factors are parameters used by the solver. See the manual for mathematical definitions.

Usually you reduce the under-relaxation factors to stabilize the solution in order to achieve convergence.

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ap
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Old   August 21, 2003, 10:05
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prasat
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thanks for the quick answers. I have one more question. In the solver define option Why steady and implict options are together. When we are going to solve for steady state we altogther neglect time right. Then why we should define implicit. prasat
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Old   August 21, 2003, 21:33
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ap
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I think you are referring to the Define->Model->Solver menu.

In the Formulation group, Implicit and Explicit options refers to the Coupled solver (Segregated solver uses implicit method).

Implicit or explicit unsteady formulation are available only if you activate the Unsteady option in the Time group.

Also, Explicit unsteady formulation is available only if you choose the coupled solver with the explicit formulation.

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ap
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Old   August 24, 2003, 11:32
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mateus
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Hi!

You have to know one thing about the underrelaxation factors that is not mentioned in Fluent documentation...you have to be really carefull when reducing the values - your simulation will become more stabil and it will probabilly converge faster, but the final solution can be unphisycal!!! You should NEVER reduce the underrelaxation to less than 0.3!!!

Regards!

MATEUS
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