Learning Forum

[davidp]

Hi Support Community,

I have a simple circular cylinder at Re 30000 but when i ask to plot drag coefficient the value is always ending around 10 instead of around 1-1.2.  The value drops initially to around 3 but recovers to the higher value before convergence.  The value is almost perfect a factor of ten high but I'm not convinced it is a calc error.  I have checked units and they are all SI.

I presume my setup is wrong but I have no clue where it is and a little frustrated.

I have a high mesh count as I'm trying to get a Y+1 solution, the problem is 2D steady, I'm using k omega SST and PISO with increased skewness correction iterations and hybrid initialization.  I have used other solvers as well but they all give around the same answer at convergence so clearly its something I've input.

Any ideas on what I've got incorrect would be greatly appreciated.

 

Cheers

 

David

[Amine Ben Hadj Ali]

Check your reference values as they are required to calculate dynamic pressure at farfield.

[davidp]

Gday Amine,

 

Thanks for your response.  Greatly appreciated.

I have adjusted the reference values to the same as the domain values for vel, viscosity and density and now the Cd is too low, argh any ideas.

David

[Amine Ben Hadj Ali]

You need to adjust to the inlet values or the reference values from the literature. Ensure for a deep converged run. Ensure that you a yplus in the viscous region a reasonable number of cells to resolve the boundary layeer (not less than 10).