[Gmsh] 2D meshing problem; extrude; 360 rotation; revolution solid.

Gustavo Charles Peixoto de Oliveira gustavo.oliveira at uerj.br
Thu Mar 26 05:49:38 CET 2015




 
 
 
Dear Gmshers, 
I'm
trying to generate a revolution solid from a cosine function profile and
sequential 2D surface meshing. Although I could get to the
surface after a rotation around the x-axis with the
'Extrude' command, Gmsh returns an error if I try to mesh
this "apparently closed" resulting solid.
My
insight is that there's a problem with
overlapped entities after the 2*pi rotation, however I
can't get rid of the error. I tried a full rotation of 2*pi and 4 partial
rotations of pi/2 with the same profile, but
both the strategies haven't work,
while non-overlapping angles ( < 2*pi) have produced the
expected mesh.
Could someone help me
to understand what's going wrong and how can I have the mesh working?
Or maybe an alternative way. The .geo
is like below. 
Thankfully,

	 

	/* Defaults */

	Geometry.Surfaces = 1; //

 
 
 

	 

	/* Settings */ 

	x0 = 0.0;

	y0 = 0.0;

	z0 = 0.0;

	c1 = 0.05;

	amp = 0.05; 

	r1 = 0.5*amp; 

	t0 = 2.0;

	R0 = 0.5;

	lambda = 2*R0;

	L = lambda;

	 

	/* Discretization */

	np = 10;

	nt = 10;

	dx = L/(np - 1);

	Geometry.ExtrudeSplinePoints = nt;

	 

	// initial point

	X[0] = x0 - lambda/2;

	Y[0] = y0 + r1;

	P0 = newp;

	P[0] = P0;

	Point(P0) = {X[0],Y[0],z0,c1};

	 

	// 'revolution' profile 

	For p In {1:np-1}

	X[p] = X[0] + p*dx;

	Y[p] = Y[0] + amp*Sinh(t0)*(1.0 + Cos(2*Pi*X[p]/lambda) );

	Pp = newp;

	Point(Pp) = {X[p],Y[p],z0,c1};

	P[p] = Pp;

	L = newl;

	Line(L) = {P[p-1],P[p]};

	extr[] = Extrude{ {0,0,0}, {1,0,0}, {0,0,0}, 2*Pi }{ Line{L};};

	EndFor

	 

	/* Same profiles adapted for partial pi/2 revolution  

	Y[0] = y0 - r1;

	P0 = newp;

	P[0] = P0;

	Point(P0) = {X[0],Y[0],z0,c1};

	 

	For p In {1:np-1}

	X[p] = X[0] + p*dx;

	Y[p] = Y[0] - amp*Sinh(t0)*(1.0 + Cos(2*Pi*X[p]/lambda) );

	Pp = newp;

	Point(Pp) = {X[p],Y[p],z0,c1};

	P[p] = Pp;

	L = newl;

	Line(L) = {P[p-1],P[p]};

	extr[] = Extrude{ {0,0,0}, {1,0,0}, {0,0,0}, Pi/4 }{ Line{L};};

	EndFor

	 

	Z[0] = z0 + r1;

	P0 = newp;

	P[0] = P0;

	Point(P0) = {X[0],y0,Z[0],c1};

	 

	For p In {1:np-1}

	X[p] = X[0] + p*dx;

	Z[p] = Z[0] + amp*Sinh(t0)*(1.0 + Cos(2*Pi*X[p]/lambda) );

	Pp = newp;

	Point(Pp) = {X[p],y0,Z[p],c1};

	P[p] = Pp;

	L = newl;

	Line(L) = {P[p-1],P[p]};

	extr[] = Extrude{ {0,0,0}, {1,0,0}, {0,0,0}, Pi/4 }{ Line{L};};

	EndFor

	 

	Z[0] = z0 - r1;

	P0 = newp;

	P[0] = P0;

	Point(P0) = {X[0],y0,Z[0],c1};

	 

	For p In {1:np-1}

	X[p] = X[0] + p*dx;

	Z[p] = Z[0] - amp*Sinh(t0)*(1.0 + Cos(2*Pi*X[p]/lambda) );

	Pp = newp;

	Point(Pp) = {X[p],y0,Z[p],c1};

	P[p] = Pp;

	L = newl;

	Line(L) = {P[p-1],P[p]};

	extr[] = Extrude{ {0,0,0}, {1,0,0}, {0,0,0}, Pi/4 }{ Line{L};};

	EndFor

	*/

 
 
 
--

Gustavo PEIXOTO DE OLIVEIRA, Dr.

State University of Rio de Janeiro

 


 


 
 
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