finite volume solver problem

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 June 20, 2012, 06:24 finite volume solver problem #1 Member   ufocfd Join Date: Jun 2012 Posts: 36 Rep Power: 7 I am developing a uniform compressible finite volume solver, Runs ok when using a cell size of 2.0 but somethings going wrong when I reduce the cell size to 0.1 units. I think the CFL & timestep specification is ok but I think its related to the update of the Q vector: RHS = dE/dx + dF/dy + dG/dz Q(n+1) = Q(n) + RHS*dt/vol, where dt = timestep and vol = cell volume Is this correct ? Have I missed something obvious ? Thanks.

June 20, 2012, 06:37
#2
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Filippo Maria Denaro
Join Date: Jul 2010
Posts: 3,819
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Quote:
 Originally Posted by ufocfd I am developing a uniform compressible finite volume solver, Runs ok when using a cell size of 2.0 but somethings going wrong when I reduce the cell size to 0.1 units. I think the CFL & timestep specification is ok but I think its related to the update of the Q vector: RHS = dE/dx + dF/dy + dG/dz Q(n+1) = Q(n) + RHS*dt/vol, where dt = timestep and vol = cell volume Is this correct ? Have I missed something obvious ? Thanks.
I see a discrepancy, dimensionally your equation is not correct ...

If V is your Volume, then the equation writes:

d/dt [Integral_V Q dV] + Integral_V Div Flux dV = 0

Therefore:

d/dt [Q_average] + (1/vol) Integral_V Div Flux dV = 0

Hence, your RHS must be vol*(dE/dx + dF/dy + dG/dz)

 June 20, 2012, 10:15 #3 Member   ufocfd Join Date: Jun 2012 Posts: 36 Rep Power: 7 thanks very much FMD !

 Tags finite volume, rhs update, solver error

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