Courant in axisymmetric simulations
 

Hi foamers


I am currently trying to simulate an axis-symmetrical set-up using wedge. Because of the wedge-like shape, some cells become very small. I tried to solve this using the simpleGrading which makes the cells near the axis longer (in r-direction) than the cells further away from the axis. However, I still get very long calculation times.


Is there any other method which I can apply to reduce the calculation time?


I am using a wedge of 1°, so the cells are also very thin. I could increase this to 5 degrees, but I am not sure whether:
- the calculation time will decrease significantly?
- this has any influence on the accuracy of the simulation?


Thank you in advance


Best regards
Arne

Is your mesh 2d, or 3d? What does meshCheck say?

Hi yambanshee


Thank you very much for your reply.



My mesh is 2D, which I thought was obligated when using the wedge-boundary conditions?


I did not try checkMesh yet, my mesh works since the calculations run, they just run very slowly because of the Courant Number in the cells at the axis.
I will try checkMesh immediatly and I will let you know the results.


Best regards
Arne

__________________________________________________ __________________________________________________ ________________________________


EDIT: I just tried checkMesh and he results are below. This mesh was made with blockMesh and had a simpleGrading of (1 1 1).




/*---------------------------------------------------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: v1806 |
| \\ / A nd | Web: www.OpenFOAM.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
Build : v1806
Arch : "LSB;label=32;scalar=64"
Exec : checkMesh
Date : Mar 06 2019
Time : 09:26:36
Host : "ea10c417"
PID : 672
I/O : uncollated
Case : /mnt/c/Users/arsimons/Documents/OpenFOAM_local/simulaties/AA_Geometry/Wedge
nProcs : 1
trapFpe: Floating point exception trapping enabled (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster (fileModificationSkew 10)
allowSystemOperations : Allowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create mesh for time = 0

Time = 0

Mesh stats
points: 20301
internal points: 0
faces: 40050
internal faces: 19750
cells: 10000
faces per cell: 5.98
boundary patches: 6
point zones: 0
face zones: 0
cell zones: 0

Overall number of cells of each type:
hexahedra: 9800
prisms: 200
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 0
polyhedra: 0

Checking topology...
Boundary definition OK.
Cell to face addressing OK.
Point usage OK.
Upper triangular ordering OK.
Face vertices OK.
Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
Patch Faces Points Surface topology
axis 0 0 ok (empty)
rightWall 200 402 ok (non-closed singly connected)
lowerWall 50 101 ok (non-closed singly connected)
atmosphere 50 101 ok (non-closed singly connected)
back 10000 10251 ok (non-closed singly connected)
front 10000 10251 ok (non-closed singly connected)

Checking faceZone topology for multiply connected surfaces...
No faceZones found.

Checking basic cellZone addressing...
No cellZones found.

Checking geometry...
Overall domain bounding box (0 0 -0.0174) (0.05 0.2 0.0174)
Mesh has 2 geometric (non-empty/wedge) directions (1 1 0)
Mesh has 3 solution (non-empty) directions (1 1 1)
Wedge back with angle 19.1879 degrees
Wedge front with angle 19.1879 degrees
All edges aligned with or perpendicular to non-empty directions.
Boundary openness (7.25056e-14 -3.85576e-18 1.36653e-17) OK.
Max cell openness = 2.21273e-16 OK.
Max aspect ratio = 2 OK.
Minimum face area = 3.48e-07. Maximum face area = 3.48e-05. Face area magnitudes OK.
Min volume = 3.48e-10. Max volume = 3.4452e-08. Total volume = 0.000174. Cell volumes OK.
Mesh non-orthogonality Max: 0 average: 0
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 0.869726 OK.
Coupled point location match (average 0) OK.

Mesh OK.

End