# Overset problem with directionMixed for overlapping boundaries

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October 10, 2019, 15:36
Overset problem with directionMixed for overlapping boundaries
#1
New Member

MI
Join Date: Apr 2018
Posts: 5
Rep Power: 7
Hi guys, I hope someone can help me with this.

I want to use overPimpleDyFoam for solving the problem of a sphere moving in a fluid. I could do it using the tutorials of OpenFoam. I also could do it for the symmetric case and solved it for half-domain. (Picture below). I defined the overlapping boundaries on the background mesh and overset grid (top boundaries in the picture) as symmetryPlane and everything works fine.

The problem is when I want to use directionMixed bc on these two boundaries the simulation does not converge because it cannot satisfy the continuity equation.

As far as I know, the boundary condition of directionMixed that I am using exactly simulates the symmetryPlane bc but it does NOT work.

interface
{
type directionMixed;
refValue uniform (0 0 0);
valueFraction uniform (0 0 0 0 0 1);
}

(du/dz = 0, dv/dz =0 , w = 0 )

ERORR:

DILUPBiCGStab: Solving for p, Initial residual = 1, Final residual = 9.12448e+22, No Iterations 1000
time step continuity errors : sum local = 89832.8, global = 454.523, cumulative = 454.523
DILUPBiCGStab: Solving for p, Initial residual = 0.000122361, Final residual = 3.59197e+13, No Iterations 1000
time step continuity errors : sum local = 9.8101e+35, global = -1.03784e+34, cumulative = -1.03784e+34
ExecutionTime = 7.95 s ClockTime = 10 s

Courant Number mean: 1.4044e+36 max: 3.90299e+39
Time = 0.01

inverseDistance : detected 2 mesh regions
zone:0 nCells:13500 voxels:(37 37 37) bb:(-10 -10 -3e-05) (10 10 10)
zone:1 nCells:41175 voxels:(37 37 37) bb:(-4.99997 -5.00002 -1.5e-05) (5.00007 5.00002 5.00002)
Overset analysis : nCells : 54675
calculated : 0
interpolated : 0 (interpolated from local:0 mixed local/remote:0 remote:0)
hole : 54675

--> 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.
Total flux : 2.28424e+55
Specified mass inflow : 1.46417e+55
Specified mass outflow : 6.8255e-19
Attached Images
 SS.jpg (62.1 KB, 20 views)

 Tags directionmixed, interface, openfoam, overset