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March 31, 2014, 11:56 |
boundary conditions and artificial viscosity
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#1 |
Senior Member
Joachim
Join Date: Mar 2012
Location: Paris, France
Posts: 145
Rep Power: 15 |
Hey everyone!
I am using the Jameson dissipation terms in my solver, and I was wondering what to do at the boundaries. I read in some papers that the dissipation was sometime set to zero at the wall. Why is that so? why shouldn't I compute the value of the dissipation term at the wall assuming that u = 0 (viscous)? I guess that at the inlet/outlet, I can simply compute the dissipation terms from the boundary values. Any suggestions?? Thanks! Joachim |
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March 31, 2014, 12:20 |
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#2 | |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,768
Rep Power: 71 |
Quote:
artificial dissipation is just a trick to stabilize the numerical solution across zones where strong gradients are present and can generate oscillations, so it should be added only locally |
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March 31, 2014, 13:18 |
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#3 |
Senior Member
Joachim
Join Date: Mar 2012
Location: Paris, France
Posts: 145
Rep Power: 15 |
Thanks for your answer!
However, I am using a central scheme for my convective terms (+RK order 4), so that I need fourth order artificial viscosity to remove any odd/even decoupling. |
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March 31, 2014, 13:26 |
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#4 | |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,768
Rep Power: 71 |
Quote:
but artificial dissipation is modulated by the local gradient intensity... do you have strong gradients as BC.s? |
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March 31, 2014, 13:32 |
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#5 |
Senior Member
Joachim
Join Date: Mar 2012
Location: Paris, France
Posts: 145
Rep Power: 15 |
well, I am computing the flow over a laminar flat plate right now, so I have gradients at the wall...
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March 31, 2014, 13:51 |
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#6 |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,768
Rep Power: 71 |
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March 31, 2014, 13:54 |
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#7 |
Senior Member
Joachim
Join Date: Mar 2012
Location: Paris, France
Posts: 145
Rep Power: 15 |
I have the values at time step n, and I explicitly compute the fluxes to get the state vector at time step n+1. However, I don't know if I should include the artificial viscosity at the wall or not...
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