[cheng1988sjtu]

Hi All:

I've spent some time interpreting the UEqn.C of twoPhaseEulerFoam. The momentum equation seems OK. however, the drag term seems problematic:

See the following link for the standard momentum equation.
http://openfoamwiki.net/index.php/BubbleFoam

In the UEqn.H, the momentum equation is :

00022 UaEqn =
00023 (
00024 (scalar(1) + Cvm*rhob*beta/rhoa)*
00025 (
00026 fvm::ddt(Ua)
00027 + fvm::div(phia, Ua, "div(phia,Ua)")
00028 - fvm::Sp(fvc::div(phia), Ua)
00029 )
00030
00031 - fvm::laplacian(nuEffa, Ua)
00032 + fvc::div(Rca)
00033
00034 + fvm::div(phiRa, Ua, "div(phia,Ua)")
00035 - fvm::Sp(fvc::div(phiRa), Ua)
00036 + (fvc::grad(alpha)/(fvc::average(alpha) + scalar(0.001)) & Rca)
00037 ==
00038 // g // Buoyancy term transfered to p-equation
00039 - fvm::Sp(beta/rhoa*K, Ua) //Drag term
00040 //+ beta/rhoa*K*Ub // Explicit drag transfered to p-equation
00041 - beta/rhoa*(liftCoeff - Cvm*rhob*DDtUb)
00042 );
00043
00044 UaEqn.relax();
00045 }

The drag term should involve the difference between Ua and Ub, not just Ua.

I've tried to implement that (Ub-Ua), I just added the following line in the rhs:

+ fvm::Sp(beta/rhoa*K, Ub)
For the UbEqns, I've done a similar modification
Am I right? Anyone can help?