Why rho coeffs are zero in compressible solvers?

immortality · December 7, 2012, 05:18

in any comressibe solver like rhoCentralFoam and rhoPimpleFoam i have run
The rho residual coeffs are zero.why it is so?
And is it possible to see rho field in results without need for making changes in solver?

piccinini · December 9, 2012, 07:58

Hello, it is probably because density is being computed explicitly, using past time step values for phi field.

immortality · December 10, 2012, 02:49

thank you dear piccinini.but how about rhoCentralFoam?why rho,rhoE,rhoUx,etc coefficients are zero?in this solver rho Fields are calculeted from continuity because it is a density based solver.

piccinini · December 10, 2012, 19:04

yes, that's right. continuity equation is being solved, but in an explicit manner.

e.g.

Code:

        solve
        (
            fvm::ddt(rhoE)
          + fvc::div(phiEp)
          - fvc::div(sigmaDotU)
        );

immortality · December 11, 2012, 03:04

thanks dear piccinini.but could you explain more about explicit solution of rho?zero coeffs how are composed?and then how can i plot rho field in paraview or other plotters?

immortality · December 14, 2012, 12:09

thank you piccinini.but whats the difference between a density based and a pressure based solver?both calculate rho from other previous fields?and then why the zeros are showing from start to end?could you tell me what have openfoam providers been intended of this displaying manner?

December 7, 2012, 05:18	Why rho coeffs are zero in compressible solvers?	#1
immortality Senior Member Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 26	in any comressibe solver like rhoCentralFoam and rhoPimpleFoam i have run The rho residual coeffs are zero.why it is so? And is it possible to see rho field in results without need for making changes in solver?

December 10, 2012, 19:04		#4
piccinini New Member Join Date: Mar 2009 Location: Sao Jose dos Campos, Brazil Posts: 29 Rep Power: 17	yes, that's right. continuity equation is being solved, but in an explicit manner. e.g. Code: solve ( fvm::ddt(rhoE) + fvc::div(phiEp) - fvc::div(sigmaDotU) );

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December 9, 2012, 07:58		#2
piccinini New Member Join Date: Mar 2009 Location: Sao Jose dos Campos, Brazil Posts: 29 Rep Power: 17	Hello, it is probably because density is being computed explicitly, using past time step values for phi field.

December 10, 2012, 02:49		#3
immortality Senior Member Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 26	thank you dear piccinini.but how about rhoCentralFoam?why rho,rhoE,rhoUx,etc coefficients are zero?in this solver rho Fields are calculeted from continuity because it is a density based solver.

December 11, 2012, 03:04		#5
immortality Senior Member Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 26	thanks dear piccinini.but could you explain more about explicit solution of rho?zero coeffs how are composed?and then how can i plot rho field in paraview or other plotters?

December 14, 2012, 12:09		#6
immortality Senior Member Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 26	thank you piccinini.but whats the difference between a density based and a pressure based solver?both calculate rho from other previous fields?and then why the zeros are showing from start to end?could you tell me what have openfoam providers been intended of this displaying manner?