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Adding a time-varying momentum source term to pimpleDyMFoam

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Old   April 15, 2015, 12:41
Question Adding a time-varying momentum source term to pimpleDyMFoam
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Pruthvi
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Hello everybody.

I'm trying to simulate a flapping airfoil with plunge amplitudes as high as 2 chords. Mesh deformation seems to be infeasible for this purpose. Therefore I want to implement the method used by Kinsey and Dumas (2008). They have added a time-varying momentum source term to the Ueqn and also time-varying velocity inlets to the top,bottom and inlet patches. The body force term is independent of space. This is basically a solver in a non-inertial frame of reference. The pitching motion is taken care of by a rotating AMI.

I want to validate the pimpleFoam solver in the non-inertial frame before I proceed to pimpleDyMFoam. I modified the solver as follows by following some previous posts in the forum.

I added an explicit source term to the right hand side of Ueqn as follows

Code:
solve(UEqn() == -g -fvc::grad(p));
g is the time varying body force defined as follows

Code:
 g=gunits*Foam::cos(runTime.value()*freQ)*vector(0,1,0);
I ran a simulation using the modified solver which is available here. The flow field seems to be reasonable but the value of forceCoeffs is much smaller than the actual value and also very erratic. Check out the forceCoeff plots below.

Cy_non_inertial.png // Non-inertial plot

forceCoeffs_flatplate.jpg // Dynamic Mesh plot

I want to know if there is any mistake in this implementation.

Here is a flow field of the same case using a dynamic mesh.

Do I need to add the body force term to the fvSchemes file? I didn't because 'g' is just a known constant.

Did anybody implement this before? I will be glad to hear your suggestions.

The case file is available here.

Thanks,
Pruthvi.
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Last edited by pruthvi1991; April 15, 2015 at 12:48. Reason: renamed attachments
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Old   April 15, 2015, 16:05
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ali alkebsi
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I dont know if what im saying makes sense or not but since you want any suggestion

When changing the momentum equation, shouldn't the pressure correction and flux correction be changed as well?
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Old   April 16, 2015, 13:03
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Pruthvi
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Hi Ali,

I don't know if I should or shouldn't. Can you explain why I should?
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Old   September 11, 2018, 14:04
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JSR
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Do you solve that issue? I am also working on the same type of problem.
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Old   June 21, 2021, 11:02
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Shuo Mi
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Quote:
Originally Posted by JSR View Post
Do you solve that issue? I am also working on the same type of problem.
Hello,

Have you solved the problem?
Thanks.
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kinsey and dumas, modified solver, pimpledymfoam, source term, validation

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