Learning Forum

[Luca Capitelli]

I follow the steps about the vorticity on a cylinder /courses/index.php/courses/unsteady-flow-past-a-cylinder/lessons/numerical-results-lesson-5-3/, now the vorticity appears but my result is strange because the turbulence is not as it should be for Re = 10000. This is the result after 277 seconds. Could it depend on the solution method? I used simple one with default options and simplec with all options at the second order.

 

[Rob]

Is the cylinder a metre diameter? The experiment is usually about 25mm (one inch). Check the other boundary conditions. How does the velocity field look?

[Luca Capitelli]

The cylinder is a meter diameter, the only boundary condition I put is the velocity inlet. I used water liquid. This is the velocity contour:

[Rob]

That looks very stable, so I'm not sure you're going to see much in the way of shedding. How does the convergence look?

[Luca Capitelli]

(it's not finished)

[Rob]

No, but it's looking like it's heading for a single stable result. Predicting shedding can be hard, is the mesh sufficiently refined? 

[Luca Capitelli]

I have a mesh with 232000 cells and 128500 nodes. I used edge sizing about 20 mm on the cylinder with growth rate 1,2. Then I used inflation with first layer thickness of 2 mm, 150 max layers and growth rate of 1. May I increase the cell number?

[Rob]

You may need to. Have a look at adaption too, you may not need to revert to meshing. I'd also try doubling the flow speed to see what happens.