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Lid Driven Cavity FSI: Continuity error cannot be removed by adjusting the outflow.

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Old   February 9, 2018, 02:26
Default Lid Driven Cavity FSI: Continuity error cannot be removed by adjusting the outflow.
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saurabh shubham
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Hi,
I am new to openFoam. I am trying to run a lid driven cavity case with a vertical rectangular block in between, using FoamExtend.

This is the error I am getting:

Time = 0.01, iteration: 2
Current fsi under-relaxation factor: 0.01
Maximal accumulated displacement of interface points: 0.000260251
Courant Number mean: 0.0100219 max: 0.905439 velocity magnitude: 0.455274
BiCGStab: Solving for Ux, Initial residual = 0.0169969, Final residual = 3.79187e-07, No Iterations 3
BiCGStab: Solving for Uy, Initial residual = 0.036895, Final residual = 1.31522e-07, No Iterations 3


--> FOAM FATAL ERROR:
Continuity error cannot be removed by adjusting the outflow.
Please check the velocity boundary conditions and/or run potentialFoam to initialise the outflow.
Specified mass inflow : 3.45746e-09
Specified mass outflow : 2.14369e-06
Difference : 2.14023e-06
Adjustable mass outflow : 0


From function adjustPhi
(
surfaceScalarField& phi,
const volVectorField& U,
const volScalarField& p
)
in file cfdTools/general/adjustPhi/adjustPhi.C at line 150.

FOAM exiting
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Old   February 14, 2018, 05:47
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Philip Cardiff
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Quote:
Originally Posted by saurabhshubham View Post
Hi,
I am new to openFoam. I am trying to run a lid driven cavity case with a vertical rectangular block in between, using FoamExtend.

This is the error I am getting:

Time = 0.01, iteration: 2
Current fsi under-relaxation factor: 0.01
Maximal accumulated displacement of interface points: 0.000260251
Courant Number mean: 0.0100219 max: 0.905439 velocity magnitude: 0.455274
BiCGStab: Solving for Ux, Initial residual = 0.0169969, Final residual = 3.79187e-07, No Iterations 3
BiCGStab: Solving for Uy, Initial residual = 0.036895, Final residual = 1.31522e-07, No Iterations 3


--> FOAM FATAL ERROR:
Continuity error cannot be removed by adjusting the outflow.
Please check the velocity boundary conditions and/or run potentialFoam to initialise the outflow.
Specified mass inflow : 3.45746e-09
Specified mass outflow : 2.14369e-06
Difference : 2.14023e-06
Adjustable mass outflow : 0


From function adjustPhi
(
surfaceScalarField& phi,
const volVectorField& U,
const volScalarField& p
)
in file cfdTools/general/adjustPhi/adjustPhi.C at line 150.

FOAM exiting
Hi Saurabh,

I guess the challenge here is that your fluid domain is fully closed (no inlet or outlet) and you are assuming an incompressible fluid, which can be difficult for Dirichlet-Neumann FSI coupling procedures: this is because a change in the fluid interface position must not change the total volume of the fluid domain. There are other coupling methods that may work better in this case e.g. see presentation by Željko Tukovic at the OFW11: http://openfoam-extend.sourceforge.n...ributions.html: "ADDED MASS PARTITIONED FLUID-STRUCTURE INTERACTION SOLVER BASED ON ROBIN BOUNDARY CONDITION FOR PRESSURE".

If it helps, I have set up a one-way coupled version of the cavity case with flexible walls: if you PM me your email, I will send it to you.

Philip
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Old   February 20, 2018, 02:58
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saurabh shubham
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Hi Philip Cardiff,

Thanks for your reply.
I solved the problem. For the initial one frame i changed the pressure outlet condition as:
outlet
{
type fixedValue;
value uniform 0;
}
after that I quickly changed it to:

outlet
{
type extrapolatedPressure;
value uniform 0;
}

And it worked
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