[BPeters]

Running this simple script in gmsh 4.0.4 for generating a mesh for a screw feeder e.g. basically cyndrical outline yields a very strange outline that deviates much from a circle.


cl1 = 1;
shift=-0.081;
timesPi=2.0;

// points
Point(1) = {0, 0.002, 0, cl1};
Point(2) = {0, 0.002, 0.08, cl1};
Point(3) = {0, 0.045, 0.08, cl1};
Point(4) = {0, 0.045, 0.0, cl1};

Line(1) = {1, 2};
Line(2) = {2, 3};
Line(3) = {3, 4};
Line(4) = {4, 1};
Line Loop(1) = {1, 2, 3, 4};

Plane Surface(1) = {1};

surfaceVector1[] = Extrude {{0, 0, shift}, {0, 0, 1}, {0, 0, 0}, 2*Pi} {
Surface{1}; Layers{20};
};




Any suggestion to get it into a circular outline is welcomed.

[BM_CFD]

I believe this video is addressing your problem which is translating and rotation. Although the video in German I believe you can still understand it. If you still have problem after watching, let me know.

Batu

[BPeters]

I know this video and it uses smaller angles. Even if I use smaller angles say Pi/2 the distortion is still there. My application is similar to generating a helical coil with a rectangular cross-section.

Here the geo script for a quick check:


cl1 = 1;
shift=-0.081;
timesPi=2.0;

// points
Point(1) = {0, 0.002, 0, cl1};
Point(2) = {0, 0.002, 0.08, cl1};
Point(3) = {0, 0.045, 0.08, cl1};
Point(4) = {0, 0.045, 0.0, cl1};

Line(1) = {1, 2};
Line(2) = {2, 3};
Line(3) = {3, 4};
Line(4) = {4, 1};
Line Loop(1) = {1, 2, 3, 4};

Plane Surface(1) = {1};

surfaceVector1[] = Extrude {{0, 0, shift}, {0, 0, 1}, {0, 0, 0}, 2*Pi} {
Surface{1}; Layers{20};
};