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 cctv August 19, 2013 11:06

Hi
I find in icoDyMFoam, there are some operation about fvc::makeRelative(phi, U) and fvc::makeAbsolute(phi, U), I know what it means, but do not know why to do this. Who can told me the reason or provide me some papers about this? Thanks.
Yu

 mkraposhin August 19, 2013 15:15

You must refer to Ferziger and Peric "Computational Fluid Dynamics" where they presented generalization for the Reynolds Transport Theorem for the moving control volume

Another good article:
"Dynamic Mesh Handling in OpenFOAM" by H. Jasak, try to google it

 cctv August 19, 2013 15:55

Quote:
 Originally Posted by mkraposhin (Post 446745) You must refer to Ferziger and Peric "Computational Fluid Dynamics" where they presented generalization for the Reynolds Transport Theorem for the moving control volume Another good article: "Dynamic Mesh Handling in OpenFOAM" by H. Jasak, try to google it
Thank you for your reply. I have ever read the article "Dynamic Mesh Handling in OpenFOAM" by H. Jasak, but I do not think he explained the reason to use fvc::makeRelative(phi, U) and fvc::makeAbsolute(phi, U) in details, In additon, do you know what would the function 'meshphi(U)' return ? Thank you very much.

 mkraposhin August 19, 2013 17:14

Quote:
 Originally Posted by cctv (Post 446754) Thank you for your reply. I have ever read the article "Dynamic Mesh Handling in OpenFOAM" by H. Jasak, but I do not think he explained the reason to use fvc::makeRelative(phi, U) and fvc::makeAbsolute(phi, U) in details, In additon, do you know what would the function 'meshphi(U)' return ? Thank you very much.
for any extensive property B and intensive property b we can write:

DB/Dt=D/Dt(int (rho*beta)dV) + int (rho*beta*(Ua-Ub))*dS

Ua - absolute velocity
Ub - velocity of the control volume boundary element
Ur=Ua-Ub - relative
D/Dt - material derivative
int (*) dV - integral over volume
int (*) dS - integral over surface

In OpenFOAM fvc::makeRelative(phi,U) estimates relative flux Ur=Ua-Ub
fvc::makeAbsolute(phi,U) estimates total flux Ua = Ur + Ub
Function fvc::meshPhi(U) returns flux of the control volume boundary Ub

This functions are used to convert from/to relative fluxes to absolute when control volume is moving, see Ferziger and Peric

 cctv August 20, 2013 11:27

Quote:
 Originally Posted by mkraposhin (Post 446768) for any extensive property B and intensive property b we can write: DB/Dt=D/Dt(int (rho*beta)dV) + int (rho*beta*(Ua-Ub))*dS Ua - absolute velocity Ub - velocity of the control volume boundary element Ur=Ua-Ub - relative D/Dt - material derivative int (*) dV - integral over volume int (*) dS - integral over surface In OpenFOAM fvc::makeRelative(phi,U) estimates relative flux Ur=Ua-Ub fvc::makeAbsolute(phi,U) estimates total flux Ua = Ur + Ub Function fvc::meshPhi(U) returns flux of the control volume boundary Ub This functions are used to convert from/to relative fluxes to absolute when control volume is moving, see Ferziger and Peric
Got it . Thank you very much.

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