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-   -   How to add time varying body force (http://www.cfd-online.com/Forums/openfoam-solving/60440-how-add-time-varying-body-force.html)

hsieh November 1, 2005 09:40

Hi, How to add a time varyi
 
Hi,

How to add a time varying body force into the solver? Can anyone suggest point to me a direction?

pei-ying

hsieh November 4, 2005 18:16

Hi, OK, no one answered thi
 
Hi,

OK, no one answered this question. But, I found something. This is what I did:

dimensionedVector BF
(
"BF", dimensionSet(0,1,-2,0,0), vector(0,1,0)
);

BF = amplitude * (Foam::sin(2.0 * 3.14 * runTime.value()/0.001)) * BF;

Info<< "bodyForce:" << BF << endl;

// Pressure-velocity PISO corrector
{
// Momentum predictor

fvVectorMatrix UEqn
(
fvm::ddt(U)
+ fvm::div(phi, U)
+ turbulence->divR(U)
);

solve(UEqn == BF -fvc::grad(p));

Pei

daveatstyacht July 26, 2010 11:43

A question about applying moments to an object
 
I am looking to apply a varying moment to a dynamic mesh problem where the value of the "force" creating the moment is equal to the force acting on the object, but offset at a distance to produce a moment (fixed distance application point for the moment, but not actually acting on the surface of the mesh). Would the method employed here be applicable to that and if so is it a matter of just changing the units to force*distance where the force is that of the current time step (or even previous time step) multiplied by a predefined distance? I am trying to set the driving force of a sail equal to the resistance acting on the hull of a vessel but acting at the center of effort of the sail and hence creating a trimming moment.

-Dave


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