About the dimension of Saffman-Mei particle lift force model
I'm working with flows with discrete, Lagrangian, particles in OpenFOAM. In the latest 2.2-release of OF, there is a particle lift force model, i.e. cross-stream forces on particles from velocity gradients.
However, I am slightly unsure if the implemented force model can be correct. I have not yet filed a bug report on it, in case my interpretation of the code is wrong. The piece of code I am looking at is found in src/lagrangian/intermediate/submodels/Kinematic/ParticleForces/Lift/LiftForce/LiftForce.C, line 144: Code:
value.Su() = mass/p.rho()*p.d()/2.0*p.rhoc()*Cl*((p.Uc() - p.U())^curlUc); The "correct" behaviour can for example be seen in src/lagrangian/intermediate/submodels/Kinematic/ParticleForces/Gravity/GravityForce.C: Code:
value.Su() = mass*g_*(1.0 - p.rhoc()/p.rho()); Does any of you have any reasonable explanation on how the expression in LiftForce.C can be correct? |
I have now come to the conclusion that it defineatly is a bug in the above mentioned piece of code. The bug is reported here: http://www.openfoam.org/mantisbt/view.php?id=822
For the reference, removing the particle diameter from the expression gives you the correct force. See the bug report above for details. The corrected line of code then become: Code:
value.Su() = mass/p.rho()*p.rhoc()/2*Cl*((p.Uc() - p.U())^curlUc); |
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