CFD Online Logo CFD Online URL
Home > Forums > OpenFOAM Running, Solving & CFD

How to add bodyforce in momentum equation in viscoelasticFluidFoam?

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Display Modes
Old   April 9, 2013, 10:03
Default How to add bodyforce in momentum equation in viscoelasticFluidFoam?
New Member
Join Date: Mar 2013
Posts: 1
Rep Power: 0
arshoon is on a distinguished road

I'm using a copy of free code(downloaded from to simulate

viscoelastic fluid in OpenFoam. The main function includes two decoupling equation: viscoelastic stress

equation and momentum equation, and I make a little change to momentum equation to add bodyforce to drive

the fluid. The equations are listed as follows:
1.UEqn(momentum equation) added bodyforce:
tmp<fvVectorMatrix> UEqn
+ fvm::div(phi, U)
+ fvc::laplacian(kappa/rho, U)
- fvm::laplacian((nus+kappa)/rho, U)
- fvc::div(sigmap/rho)
solve(UEqn() == -fvc::grad(p));
2.TEqn(viscolastic equation):
gradU = fvc::grad(U);
tmp<fvTensorMatrix> TEqn
+ fvm::div(phi,sigmap)
nup/lambda1*(gradU + gradU.T())
+ (sigmap & gradU) + (gradU.T() & sigmap)
- (fvm::Sp(epsilon/nup*tr(sigmap), sigmap) + fvm::Sp(1/lambda1,sigmap))
- (xi/1)*( (gradU & sigmap) + (sigmap & gradU.T()) + (gradU.T() & sigmap) + (sigmap &

// TEqn().relax();
I start from 2D poiseuille flow,Initial U is set to zero, and the inlet and outlet of the tube are defined

as cyclic boundary.
I carried out two simulations with the same physic parameters but different mesh sizes, one is 100by50, the

other is 200by100, then I output the velocity profile in paraview.
To my huge surprise the maximum velocity differed a lot(U1:0.0052, U2:0.0093), and It seemed to be

impossible to be explained as space error...This problem bothered me a lot!!
I really wonder why??? Can anybody give me some advices?? Thanks very much!!

Last edited by arshoon; April 9, 2013 at 20:24.
arshoon is offline   Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
viscosity term in discetrization momentum equation hans-186 Main CFD Forum 4 April 1, 2013 13:34
solving the momentum equation in UEqn. callahance OpenFOAM 2 October 18, 2012 09:38
Derivation of k-e model from momentum equation CFDtoy Main CFD Forum 5 May 10, 2006 16:53
Guess Momentum add value Jackie Main CFD Forum 0 July 31, 2003 23:39
How to add a fixed force on momentum equation sun Phoenics 3 January 19, 2002 07:31

All times are GMT -4. The time now is 22:24.