boxlen = 2.0; boxwidth = 0.8; cylinderradius = 0.07; cylinderxpos = 0.25; // Tiny misalignment: cylinderypos = boxwidth/2 + boxwidth/1000; Mesh.CharacteristicLengthFactor = 0.05; SetFactory("OpenCASCADE"); Rectangle(1) = {0, 0, 0, boxlen, boxwidth, 0}; Disk(2) = {cylinderxpos, cylinderypos, 0, cylinderradius, cylinderradius}; Coherence; fluid = 1; cylinder = 2; inlet = 3; outlet = 4; Physical Surface(fluid) = 3; Physical Surface(cylinder) = 2; Physical Line(inlet) = 2; Physical Line(outlet) = 3;