CFD Online Discussion Forums - closed tank and dynamic mesh

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closed tank and dynamic mesh

Hi all,

I worked with rhoPimpleDyMFoam some times in non closed cases but now I have a closed volumina. Therefor I got "pcorr" step to 1000 iterations every time.

To check if this occure with closed volume cases I changed the tutorial case in the rhoPimpleDyMFoam so that there is no inlet and outlet anymore.

Its the same result. pcorr blows up:

Code:

solidBodyMotionFunctions::rotatingMotion::transformation(): Time = 0.0152941 transformation: ((0 0 0) (0.981781 (0 0 0.190014)))

AMI: Creating addressing and weights between 10944 source faces and 10944 target faces

AMI: Patch source weights min/max/average = 0.945398, 1.00512, 0.999941

AMI: Patch target weights min/max/average = 0.951965, 1.00398, 0.999942

GAMG:  Solving for pcorr, Initial residual = 0.999999, Final residual = 20.8413, No Iterations 1000

diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0

Is there any solution?
Regards
Tobi

PS: @admin - if its possible the title can be changed into "closed volume and dynamic mesh"

Hi all,

I tested my case yesterday again with a few outer faces used to be an atmosphere.

Therefor p is totalPressure and U is an pressureInletOutletVelocity. With this Addition the Simulation is running stable and fast.

pcorr is normal with a few iterations 5 - 20.

But I am still interested why pcorr blows up in closed volume cases.
Maybe I should have a look at the equations :)

Hi Tobias,

It sounds to me, as if the compressibility of the fluid is not taken into consideration by the solver/pcorr loop. You probably changed the total volume of the box, and then pcorr has a problem in putting the excess volume somewhere.

A suggestion for checking this could be as follows:

1. Set up a simple cavity test.
2a. Move the left and right boundaries with the same velocity.
2b. Move the left and right boundaries with different velocities.

Case 2a should be successful, because the total volume remains constant, and 2b should fail.

Good luck,

Niels

Hey Tobi.

I'm also dealing with a closed domain with moving boundaries. Although my model doesn't blow up, the iterations in the pcorr step are always a lot slowing down terribly the simulations.

In your (or others opinion), should a reduced level of convergence for pcorr deteriorate the accuracy of results or can we live with it?

Thanks,

R

I cannot give you any advice but you can check out - or set - the keyword that calculates the pressure correction for closed volumes. You have to add the keyword in the fvSolution file (not sure, check out the sources yourself).

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Hi,
Have you set a pRef and pRefpoint somewhere in your domain? I can't see that it should be necessary with a compressible solver though.

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Hello Tobias,

I also want to simulate a closed volume stirred tank using the solver rhoPimpleDyMFoam. Im simulating an incompressible fluid, but need the compressible version of the solver for the heat transfer simulation. As you described, the simulation runs only with one patch defined as inletOutlet. My problem is now, because its an inlet, I get a flow in and out of the domain, but I want the domain to be closed.

I defined my BC as follow:
U

Code:

    oben

    {

        type            pressureInletOutletVelocity;

        value           uniform (0 0 0);

    }

Code:

    oben

    {

        type            totalPressure;

        p0              $internalField;

        U               U;

        phi             phi;

        rho             rho;

        psi             none;

        gamma           1;

        value           $internalField;

    }

Do you know how to define the patch, that I dont get a mass flow in and out of the domain with still getting a stable simulation?

Kind regards
Michael