Superficial velocity or real fluid velocity in GidaspowDrag.C

Submitted by dbxmcf on Wed, 07/27/2016 - 04:44

Hi, All:

I am a bit confused about the Equations used to calculate the drag force term in GidaspowDrag.C:

https://github.com/CFDEMproject/CFDEMcoupling-PUBLIC/blob/master/src/lag...

in line 195:

Ufluid = U_[cellI];

Is this the superficial velocity (U_superficial = U_real*voidfraction) or the real fluid velocity? From my understanding it is real velocity, is that correct?

It seems that in this OpenFOAM workshop paper:

http://web.student.chalmers.se/groups/ofw5/Papers/ChristophGonivaPaperOF...

Equation 11 said Uf is superficial velocity, so in GidaspowDrag.C line 219-236, are we using the actual fluid velocity or the superficial velocity?

Thanks a lot for the clarifications!

Roy

Forums:

NTT1508 | Thu, 07/28/2016 - 03:18

Hi,

I believe in most drag force models, the real (duck) fluid velocity should be used. Superficial velocity is the external value and it cannot be involved in the modified Navier-Stokes equations where the porosity is incorporated. I have seen some papers using Gidaspow equation and the real velocity has been used there.

Regards,

cgoniva's picture

cgoniva | Thu, 08/25/2016 - 20:16

Hello Roy,

cfdemSolverPiso solves the conservation of div(voidfraction*U)=0, so U is the intersitial velocity.

Best regards,
Christoph