
Lesson 11 Flow over cylinder
Hi ,
I am trying flow over cylinder with fluent with fluent meshing. Given problem : water flows over 1m dia. cylinder at 50 m/s. Meshing consists of 2 zones one is the larger enclosure for setting up the flow domain and the other surrounded closer to cylinder for local sizing (i used 0.05 m, 0.1 m, 0.2 m); Mesh : polyhedra; Solver : SIMPLE solver with PRESTO! for pressure (Second order is not working for any mesh size). Minimum orthogonal quality in all cases is more than 0.4. and average is more than 0.98. The residuals are always diverging for the case of 0.05 and correspondingly TVR (turbulent viscosity ratio) is crossing the limit 1.0e5 for far too many cells in the entire downstream behind the cylinder. Next for 0.1 the residuals are converging but they look like a ball bouncing on a staircase and correspondingly the TVR crosses 1.0e5 for just behind the cylinder but not as worse as that of case 0.05 local sizing. At last, for 0.2 the residuals are converging in a straight forward way but the obvious concern would be the sizing 0.2 would not naturally describe the geometry to an appropriate resolution! but it converges. Also i tried adding and decreasing the number of boundary layers it did not effect the convergence. I tried a lot to understand but now i need help.The attached images are for reference (case 0.1 local sizing for cylinder region).
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