# Problem in blockMesh for different z_length

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November 18, 2019, 02:39
Problem in blockMesh for different z_length
#1
Member

Bidesh Sengupta
Join Date: Sep 2018
Location: Sngapore
Posts: 76
Rep Power: 7
Hi Foamers!

I am facing a strange problem while changing the height of the cylinder. I am proving the blockMeshDict file.

//meshGenApp blockMesh;
convertToMeters 1;
dia 1.48;
ll -2;
lu 0;
ori_x 0;
ori_y 0;
xdiv 30;
ydiv 50;
zdiv 60;

sq_two 1.414;

rb #calc "\$dia/2";
nrb #calc "-1*\$dia/2";
ra #calc "0.8*\$dia/4";
nra #calc "0.8*-1*\$dia/4";
b #calc "0.5*\$dia/\$sq_two";
nb #calc "-0.5*\$dia/\$sq_two";
a #calc "0.25*\$dia/\$sq_two";
na #calc "-0.25*\$dia/\$sq_two";

vertices
(
//Plane A:
(\$a \$na \$ll)//(0.0643 -0.064 -2) // Vertex A0 = 0 (dia/sq_two -dia/sq_two)
(\$a \$a \$ll)//(0.0643 0.0643 -2) // Vertex A1 = 1 (dia/sq_two dia/sq_two)
(\$na \$a \$ll)//(-0.064 0.0643 -2) // Vertex A2 = 2 (-dia/sq_two dia/sq_two)
(\$na \$na \$ll)//(-0.064 -0.0643 -2) // Vertex A3 = 3 (-dia/sq_two -dia/sq_two)
(\$b \$nb \$ll)//(0.0919 -0.0919 -2) // Vertex A4 = 4 (0.5*dia/sq_two -0.5*dia/sq_two)
(\$b \$b \$ll)//(0.09192 0.0919 -2) // Vertex A5 = 5 (0.5*dia/sq_two 0.5*dia/sq_two)
(\$nb \$b \$ll)//(-0.09192 0.0919 -2) // Vertex A6 = 6 (-0.5*dia/sq_two 0.5*dia/sq_two)
(\$nb \$nb \$ll)//(-0.09192 -0.0919 -2) // Vertex A7 = 7 (-0.5*dia/sq_two -0.5*dia/sq_two)

//Plane B:
(\$a \$na \$lu)//(0.0643 -0.064 0) // Vertex B0 = 8
(\$a \$a \$lu)//(0.0643 0.0643 0) // Vertex B1 = 9
(\$na \$a \$lu)//(-0.064 0.0643 0) // Vertex B2 = 10
(\$na \$na \$lu)//(-0.064 -0.0643 0) // Vertex B3 = 11
(\$b \$nb \$lu)//(0.0919 -0.0919 0) // Vertex B4 = 12
(\$b \$b \$lu)//(0.09192 0.0919 0) // Vertex B5 = 13
(\$nb \$b \$lu)//(-0.09192 0.0919 0) // Vertex B6 = 14
(\$nb \$nb \$lu)//(-0.09192 -0.0919 0) // Vertex B7 = 15
);

// Defining blocks:
blocks
(
//Blocks betweenplane A and plane B:
// block0 -positive x O-grid block
hex (5 1 0 4 13 9 8 12 ) (\$xdiv \$ydiv \$zdiv)simpleGrading (1 1 1)
// block1 -positive y O-grid block
hex (6 2 1 5 14 10 9 13 ) (\$xdiv \$ydiv \$zdiv)simpleGrading (1 1 1)
// block2 -negative x O-grid block
hex (7 3 2 6 15 11 10 14 ) (\$xdiv \$ydiv \$zdiv)simpleGrading (1 1 1)
// block3 -negative y O-grid block
hex (4 0 3 7 12 8 11 15 ) (\$xdiv \$ydiv \$zdiv)simpleGrading (1 1 1)
// block4 -central O-grid block
hex (0 1 2 3 8 9 10 11 ) (\$ydiv \$ydiv \$zdiv)simpleGrading (1 1 1)
);

edges
(
//Plane A:
arc 0 1 (\$ra 0 -2)
arc 1 2 (0 \$ra -2)
arc 2 3 (\$nra 0 -2)
arc 3 0 (0 \$nra -2)
arc 4 5 (\$rb 0 -2)
arc 5 6 (0 \$rb -2)
arc 6 7 (\$nrb 0 -2)
arc 7 4 (0 \$nrb -2)

//Plane B:
arc 8 9 (\$ra 0 0)
arc 9 10 (0 \$ra 0)
arc 10 11 (\$nra 0 0)
arc 11 8 (0 \$nra 0)
arc 12 13 (\$rb 0 0)
arc 13 14 (0 \$rb 0)
arc 14 15 (\$nrb 0 0)
arc 15 12 (0 \$nrb 0)
);

// Defining patches:
patches
(
patch inlet
(
(1 5 4 0)
(2 6 5 1)
(3 7 6 2)
(0 4 7 3)
(3 2 1 0)
)
patch outlet
(
(13 9 8 12)
(14 10 9 13)
(15 11 10 14)
(12 8 11 15)
(8 9 10 11)
)
wall wallDiffuser
(
(4 5 13 12)
(5 6 14 13)
(6 7 15 14)
(7 4 12 15)
)
);

While ll=-2, the mesh (Fig1) is nice. But when I am trying with ll=-0.2, it (Fig2) is very strange.
Attached Images
 Fig1.png (65.7 KB, 3 views) Fig2.png (107.6 KB, 3 views)

 November 18, 2019, 19:40 #2 Member   Bidesh Sengupta Join Date: Sep 2018 Location: Sngapore Posts: 76 Rep Power: 7 The problem was solved by changing the arc with ll and lu. Thank you.

 Tags blockmesh, foam extend, openfaom

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