[HumanistEngineer]

I am new to OpenFoam and also to GMSH.

I try to model an axisymmetric geometry for a sensible stratified heat storage tank. I need to define empty geometry at the inlet and outlet of the tank as obstacles (namely diffusers).

Please see attached geo file; when I apply 3D meshing, it works but the diffusers also get meshed with the inner medium.

Would you please help me with this issue?

Kind regards.
Hakan

[HumanistEngineer]

I could overcome this issue via subtracting the obstacle (empty) volume from the main medium volume by use of "BooleanDifference", see the code below for geo file:

SetFactory("OpenCASCADE");

// Inputs 
r_tank=2.56/2; 	// m - radius of tank
r_pipe=0.075;  	// m - radius of pipe 
r_diff=0.8; 	// m - radius of diffuser

h_tank=3.83; 	// m - tank height
h_pipe=0.25; 	// m - inlet/outlet height

h_such=0.13; 	// m - suction head

t_diff=0.005; 	// m - material thickness (diffuser and pipe)
h_diff=0.075; 	// m - diffuser gap height

grid_s=1; 	// grid size

// Geometry - Tank
Point(1) = {0,0,0,grid_s};
Point(2) = {r_pipe,0,0,grid_s};
Point(3) = {r_pipe,0,h_pipe,grid_s};
Point(4) = {r_tank,0,h_pipe,grid_s};
Point(5) = {r_tank,0,h_pipe+h_tank,grid_s};
Point(6) = {r_pipe,0,h_pipe+h_tank,grid_s};
Point(7) = {r_pipe,0,h_pipe+h_tank+h_pipe,grid_s};
Point(8) = {0,0,h_pipe+h_tank+h_pipe,grid_s};

Line(1) = {1,2};
Line(2) = {2,3};
Line(3) = {3,4};
Line(4) = {4,5};
Line(5) = {5,6};
Line(6) = {6,7};
Line(7) = {7,8};
Line(8) = {8,1};

Line Loop(1) = {1,2,3,4,5,6,7,8};

Plane Surface(0) = {1};

// Geometry - Diffuser - Bottom
Point(9) = {0,0,h_pipe+h_diff,grid_s};
Point(10)= {r_diff,0,h_pipe+h_diff,grid_s};
Point(11)= {r_diff,0,h_pipe+h_diff+t_diff,grid_s};
Point(12)= {0,0,h_pipe+h_diff+t_diff,grid_s};

Line(9) = {9,10};
Line(10)= {10,11};
Line(11)= {11,12};
Line(12)= {12,9};

Line Loop(2) = {9,10,11,12};

Plane Surface(1) = {2};

// Geometry - Diffuser - Top Plate
Point(13)= {0,0,h_tank+h_pipe-h_such-h_diff-t_diff,grid_s};
Point(14)= {r_diff,0,h_tank+h_pipe-h_such-h_diff-t_diff,grid_s};
Point(15)= {r_diff,0,h_tank+h_pipe-h_such-h_diff,grid_s};
Point(16)= {0,0,h_tank+h_pipe-h_such-h_diff,grid_s};

Line(13)= {13,14};
Line(14)= {14,15};
Line(15)= {15,16};
Line(16)= {16,13};

Line Loop(3) = {13,14,15,16};

Plane Surface(2) = {3};

// Geometry - Diffuser - Top Inlet
Point(17)= {r_pipe,0,h_tank+h_pipe-h_such-t_diff,grid_s};
Point(18)= {r_diff,0,h_tank+h_pipe-h_such-t_diff,grid_s};
Point(19)= {r_diff,0,h_tank+h_pipe-h_such,grid_s};
Point(20)= {r_pipe+t_diff,0,h_tank+h_pipe-h_such,grid_s};
Point(21)= {r_pipe+t_diff,0,h_tank+h_pipe,grid_s};

Line(17)= {17,18};
Line(18)= {18,19};
Line(19)= {19,20};
Line(20)= {20,21};
Line(21)= {21,6};
Line(22)= {6,17};

Line Loop(4) = {17,18,19,20,21,22};

Plane Surface(3) = {4};

// Union of Diffuser Surfaces

// Plane Surface (4) = BooleanUnion{ Surface{1}; Delete; }{ Surface{2,3}; Delete; };

// Subtracting Diffuser from the Main Flow Body

// Plane Surface (5) = BooleanDifference{ Surface{1}; }{ Surface{4}; Delete; };

// Rotating the Surface and Forming Volume (AxiSymmetric)
Rotate {{0,0,1},{0,0,0},-2.5*Pi/180.0}
{
	Surface {0};
}

Extrude {{0,0,1},{0,0,0},5*Pi/180.0}
{
	Surface {0};
	Layers{1};
	Recombine;
}

// Rotating the Surface and Forming Volume - diffuser (AxiSymmetric)
// BooleanUnion{ Surface{1}; Delete; }{ Surface{2,3}; Delete; }


Rotate {{0,0,1},{0,0,0},-2.5*Pi/180.0}
{
	Surface {1};
}

Extrude {{0,0,1},{0,0,0},5*Pi/180.0}
{
	Surface {1};
	Layers{1};
	Recombine;
}

BooleanDifference{ Volume{1}; Delete;}{ Volume{2}; Delete;}

Rotate {{0,0,1},{0,0,0},-2.5*Pi/180.0}
{
	Surface {2};
}

Extrude {{0,0,1},{0,0,0},5*Pi/180.0}
{
	Surface {2};
	Layers{1};
	Recombine;
}

BooleanDifference{ Volume{1}; Delete;}{ Volume{2}; Delete;}

Rotate {{0,0,1},{0,0,0},-2.5*Pi/180.0}
{
	Surface {3};
}

Extrude {{0,0,1},{0,0,0},5*Pi/180.0}
{
	Surface {3};
	Layers{1};
	Recombine;
}

BooleanDifference{ Volume{1}; Delete;}{ Volume{2}; Delete;}

Physical Surface("inlet") = {54};
Physical Surface("outlet") = {43};
Physical Surface("walls") = {44,47,58,57,55};
Physical Surface("wedge_1") = {45};
Physical Surface("wedge_2") = {46};
Physical Surface("diffuser") = {39,40,41,42,48,49,50,51,52,53,56};

Physical Volume("innerFlow") = {1}