[Alasir]

Hi

I want to start of a channel as 0 at all places, cyclic inlet and outlet, but with a constant dP/dx pressure gradient so that the fluid eventually approach a steady flow.

Anyone know how to do this using the fvOptions file?

[hulli]

Hi man

I never did it with pressure but with velocity i.e. Ubar Best H
:
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 3.0.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "constant";
object fvOptions;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

momentumSource
{
type meanVelocityForce;
active yes;

meanVelocityForceCoeffs
{
selectionMode all;

fieldNames (U);
Ubar (0.335 0 0);
}
}


// ************************************************** *********************** //

[RobertHB]

Hello Anders,
just follow Hullis example. Besides, for OpenFOAM 5.0, it has to read
fields (U); instead of fieldNames (U);
Works with transient, as well as with steady-state flows.

[Alasir]

This seems to have the disadvantage of jumping DIRECTLY to a high speed everywhere, thus making the simulation unsteady?

[RobertHB]

Sure, if your simulations becomes unstable at a certain velocity threshold, setting fvOptins/Ubar to this value will cause your solution to diverge. Otherwise there shouldn't be any problem.

[hulli]

try to play around with Ubar !!! otherwise you might have to adjust your schemes ....

[agustinvo]

Hi,

try to use the vectorSemiImplicitSource. In case of U, you introduce it as

injectionRateSuSp { U ((dpdx 0 0) 0); }

https://github.com/OpenFOAM/OpenFOAM...plicitSource.H

[HPE]

May help?

directionalPressureGradientExplicitSource

[Haitham Osman CFD]

Originally Posted by HPE

May help?

directionalPressureGradientExplicitSource

it was renamed to meanVelocityForce

https://github.com/OpenFOAM/OpenFOAM...898bec5fac74ad

kind regards