how to create a cylinder with minimal nodes and elements?

hello,

im trying to create a solid cylinder to use in the pde toolbox, with radius and height of size 1.

i tried it in several ways with functions like multicylinder,cylinder and meshgrid, but the amount of nodes and elements is too big, of about 40,000-50,000, which causes my model to run very slow.

edit - i added some of the codes i tried:

gm=multicylinder (1,1);
model.Geometry=gm;
generateMesh(model);
----

[th,r,h]=meshgrid(linspace(0,2*pi,30),[0,1],[0,1]);
[x,y,z] = pol2cart(th,r,h);
shp = alphaShape(x(:),y(:),z(:),2.5);
% plot(shp);

% applying the geometry to the model
[elements,nodes] = boundaryFacets(shp);
nodes = nodes';
elements = elements';
geometryFromMesh(model,nodes,elements);
%  pdegplot(model,'FaceLabels','on','FaceAlpha',1);

% Generate the mesh
generateMesh(model);
---

[x,y,z]=cylinder;
shp = alphaShape(x(:),y(:),z(:));
% plot(shp);

% applying the geometry to the model
[elements,nodes] = boundaryFacets(shp);
nodes = nodes';
elements = elements';
geometryFromMesh(model,nodes,elements);
pdegplot(model,'FaceLabels','on','FaceAlpha',1);

% Generate the mesh
generateMesh(model);

is there a better way? thank you

[John D'Errico]

We all want things we cannot have. A skill of mathematics is to find ways to solve problems even though brute force fails. Or, just be lazy and get a bigger, faster computer. Or accept that broadly approximate results are acceptable. But asking how to magically reduce a big problem to a small one, without even seeing the problem? That is impossible to answer.

[yonatan s]

well there isn't much to see, since setting up the geometry is the first step when using the pde toolbox.

[KSSV]

Why don't you post your code which generates your cylinder?

Answer 1

[Ravi Kumar]

You can use 'Hmax' parameter to set the target maximum element size, as explained in this documentation page for generateMesh.

For example,

model = createpde;
gm=multicylinder (1,1);
model.Geometry=gm;
generateMesh(model,'Hmax',0.2);

gives a coarse mesh with less than 3000 elements. Note that the discretization error would increase as you coarsen the mesh, particularly for geometries with curved faces/edges.

[yonatan s]

thank you, but this mesh is too coarse for me

[Ravi Kumar]

I did not suggest you should use the mesh I provided. I gave an example and link to documentation, using which you can obtain desired mesh. You need to try and find the right set of parameters that you can specify in generateMesh function call.