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November 6, 2009, 06:21 |
"Coulomb"-type BC
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#1 |
New Member
Christian Kröner
Join Date: Nov 2009
Location: Bonn
Posts: 7
Rep Power: 16 |
Hello Foamers,
i would like to use a Coulomb-Type BC for the simulation of a collapse of a granular column with interFoam. Therefore, i want to mimic a kind of stick-slip BC by utilizing the partSlip BC and introducing a calculated valueFraction. The flow at the boundary should feel an additional friction term F_c=-u_t/|u_t|*tan(delta)*N, where delta is the bottom friction angle, N the normal force acting on the Boundary and u_t is the velocity at the patch. The change in velocity due to this force could be callculated, by assuming free slip, and correcting the velocity by: u_t=u_fs - deltaT*u_fs/|u_fs| *tan(delta)*pressure*area u_t=u_fs*(1-deltaT/|u_fs|*tan(delta)*pressure*area) so i would like to calculte the valueFraction by: Code:
if(deltaT/|u_fs|*tan(delta)*pressure*area>=0){ valueFraction=deltaT/|u_fs|*tan(delta)*pressure*area } else{ valueFraction=0;} 1) Is it legal to handle the bottom friction in this way? Or is there a better way to introduce an bottom frition law? 2) I'm new to OpenFoam and, therefore, have some problems with the fundamental basics of implementing the BC. a) Can I use Code:
const Field<scalar>& magS=patch().magSf(); const fvPatchField<scalar>& pp=patch().lookupPatchField<volScalarField, scalar> ("p"); const fvPatchField<scalar>& rhop=patch().lookupPatchField<volScalarField, scalar>("rho"); scalar dt=runTime.deltaT(); b) And to calculate the valueFraction could I use: Code:
if(dt/mag(*this)*valueFraction_*magS*pp*rhop>=0){ valueFractionCalc_ = dt/mag(*this)*tandelta_*magS*pp*rhop; } else{valueFractionCalc_ =0;} Thanks a lot! Christian |
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