[Gmsh] Problem with Boundary Layer around 2D airfoil with sharp trailing edge

[DILASSER Guillaume]

Hello Ashish,

You can add to the BoundaryLayer definition the property “Field[1].FanNodesList = {1,n} ;” to get rid of the weird behavior of the mesh around the tips of the foil. Somehow, the 2D blossom recombination algorithm does not like when you do that so replace it with the standard one using “Mesh.RecombinationAlgorithm = 0 ;”. Both modifications are done in the enclosed file. Finally, you may want to increase the mesh density at the front of the foil to better match the geometry there.

Sincerely Yours,

Guillaume DILASSER
Doctorant SACM / LEAS
CEA - Centre de Saclay - Bât.123 - PC 319c
91191 Gif sur Yvette Cedex - France -

guillaume.dilasser at cea.fr<mailto:guillaume.dilasser at cea.fr>


De : gmsh [mailto:gmsh-bounces at ace20.montefiore.ulg.ac.be] De la part de ashish bhole
Envoyé : lundi 11 juillet 2016 19:02
À : gmsh at onelab.info
Objet : [Gmsh] Problem with Boundary Layer around 2D airfoil with sharp trailing edge

Hello All,
I am new at using gmsh. I want to generate a mesh (unstructured) around 2D airfoil with sharp trailing edge. When I use Boundary Layer field in gmsh, it generates boundary layer but with undesirable intersections. I have attached my .geo file here. Currently, I have commented Boundary Layer field lines in the script.
Please share idea how can I make it work correctly.
Thank you.

------------------------------------
Mesh.RecombineAll = 1;

Li = 50.0; // distance of inflow boundary from origin
Lo = 50.0; // distance of outflow boundary from origin

n  = 50; // points on upper/lower surface of airfoil used to define airfoil
         // These points may not appear in the mesh.

lc1 = 10.0;
lc2 = 0.05;

m = 2*n - 2; // total number of points on airfoil without repetition
             // LE and TE points are common to upper/lower surface

nle = n; // point number of LE = no. of points on upper surface
         // Point(1) is trailing edge

// NACA0012 profile
// formula taken from http://turbmodels.larc.nasa.gov/naca0012_val.html
Macro NACA0012
   x2 = x * x;
   x3 = x * x2;
   x4 = x * x3;
   y = 0.594689181*(0.298222773*Sqrt(x)
       - 0.127125232*x - 0.357907906*x2 + 0.291984971*x3 - 0.105174606*x4);
Return

// put points on upper surface of airfoil
For i In {1:n}
   theta = Pi * (i-1) / (n-1);
   x = 0.5 * (Cos(theta) + 1.0);
   Call NACA0012;
   Point(i) = {x, y, 0.0, lc2};
   xx[i] = x;
   yy[i] = y;
EndFor

// put points on lower surface of airfoil, use upper surface points and reflect
For i In {n+1:m}
   Point(i) = {xx[2*n-i], -yy[2*n-i], 0.0, lc2};
EndFor

Spline(1) = {1:n};
Spline(2) = {n:m, 1};

Point(1000) = {1.0, Li, 0.0,lc1};
Point(1001) = {0.0, Li, 0.0,lc1};
Point(1002) = {-Li, 0.0, 0.0,lc1};
Point(1003) = {0.0, -Li, 0.0,lc1};
Point(1004) = {1.0, -Li, 0.0,lc1};

Point(1005) = {Lo, 0.0, 0.0,lc1};
Point(1006) = {Lo, Li, 0.0,lc1};
Point(1007) = {Lo, -Li, 0.0,lc1};

Line(5) = {1000, 1001};
Circle(6) = {1001, nle, 1002};
Circle(7) = {1002, nle, 1003};
Line(8) = {1003, 1004};
Line(13) = {1005, 1006};
Line(14) = {1005, 1007};
Line(15) = {1006, 1000};
Line(16) = {1007, 1004};

Line Loop(1) = {1,2};
Line Loop(2) = {5,6,7,8,-16,-14,13,15};

Plane Surface(201) = {2,1};

/*
//Define Boundary Layer
Field[1] = BoundaryLayer;
Field[1].EdgesList = {1,2};
Field[1].NodesList = {1,m};
Field[1].hfar = 0.05;
Field[1].hwall_n = 0.009;
Field[1].thickness = 0.2;
Field[1].ratio = 1.1;
Field[1].AnisoMax = 10;
Field[1].Quads = 1;
Field[1].IntersectMetrics = 0;
BoundaryLayer Field = 1;
*/
------------------------------------

-- With Reagrds
Ashish Bhole
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