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-   -   refineWallLayer for reaching y+<1 for low Re number turbulence model (http://www.cfd-online.com/Forums/openfoam-meshing-snappyhexmesh/123697-refinewalllayer-reaching-y-1-low-re-number-turbulence-model.html)

s.m September 19, 2013 02:58

refineWallLayer for reaching y+<1 for low Re number turbulence model
 
1 Attachment(s)
Hi:)
Dear foamer i have a big promlem, i want to analysis two turbulence models on 3 element airfoil,
1. high Re number e.g realizableKE ==> 30 <y+ <200
2. low Re number e.g lunderSharmaKE ==> y+ <1
i use snappyHexMesh for meshin the domain aroun the airfoil, and after finishing the analysis with realizableKE, i execute "yPlusRAS" and it told me y+ is:
Time = 3400
Reading field U

Reading/calculating face flux field phi

Selecting incompressible transport model Newtonian
Selecting RAS turbulence model realizableKE
realizableKECoeffs
{
Cmu 0.09;
A0 4;
C2 1.9;
sigmak 1;
sigmaEps 1.2;
}

Patch 5 named main_solid y+ : min: 3.92116 max: 92.2824 average: 41.5749

Patch 6 named flap_solid y+ : min: 11.3159 max: 75.4566 average: 34.844

Patch 7 named slat_solid y+ : min: 17.4322 max: 61.5812 average: 43.726

and the checkMesh for RealizableKE doeasn't complain of skewness and nonOrthogonality,
here it is:
Create polyMesh for time = 3400

Time = 3400

Mesh stats
points: 188346
internal points: 0
faces: 368558
internal faces: 182800
cells: 91461
faces per cell: 6.02834
boundary patches: 8
point zones: 0
face zones: 0
cell zones: 0

Overall number of cells of each type:
hexahedra: 88316
prisms: 584
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 0
polyhedra: 2561
Breakdown of polyhedra by number of faces:
faces number of cells
7 1953
8 603
9 3
10 2

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
topAndBottom 496 996 ok (non-closed singly connected)
inlet 176 354 ok (non-closed singly connected)
outlet 176 354 ok (non-closed singly connected)
front 91461 94173 ok (non-closed singly connected)
back 91461 94173 ok (non-closed singly connected)
main_solid 1298 2596 ok (non-closed singly connected)
flap_solid 376 752 ok (non-closed singly connected)
slat_solid 314 628 ok (non-closed singly connected)

Checking geometry...
Overall domain bounding box (-5.84378 -11.1882 0.15) (20.9289 9.3226 0.250001)
Mesh (non-empty, non-wedge) directions (1 1 0)
Mesh (non-empty) directions (1 1 0)
***Number of edges not aligned with or perpendicular to non-empty directions: 33
<<Writing 30 points on non-aligned edges to set nonAlignedEdges
Boundary openness (4.30491e-19 -2.30373e-20 -1.93086e-13) OK.
Max cell openness = 2.10615e-16 OK.
Max aspect ratio = 6.91795 OK.
Minimum face area = 4.88326e-08. Maximum face area = 0.0100272. Face area magnitudes OK.
Min volume = 4.88326e-09. Max volume = 0.00100272. Total volume = 43.645. Cell volumes OK.
Mesh non-orthogonality Max: 62.2458 average: 3.79811
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 2.67447 OK.
Coupled point location match (average 0) OK.

Failed 1 mesh checks.

but when i execute refineWallLayer for reaching lower layer thickness near the wall and also lower y+ that was proper for lunderSharmaKE, the checkMesh complain skewness alot.
what should i do?:(:(:(
how should i yeild the low y+ with snappyhexMesh???
please guide me:(

s.m September 19, 2013 03:06

here it is some pics of adding layer to main element
 
5 Attachment(s)
here it is some pics of adding layer to the leading edge of main element

s.m September 19, 2013 03:10

5 Attachment(s)
here is some pics of adding layer to another element of 3 element airfoil (slat)

s.m September 19, 2013 03:18

5 Attachment(s)
here is some pic of slat


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