Hi , i am doing a project and the first step is benchmarking: for this we have to find drag coefficient C_d for Re=100 over cylinder of diameter 10 mm, i have created the mesh, and after solving after 100-200 iteration where convergence crtiera is met, the results are quite different from the experimental result can someone pls explain it.

Or how do i set up conditions in Fluent for the above problem of cylinder

100-200 iterations for convergence? Sounds like you're using the default values of 1e-3. You can't just go by the residuals. You need to monitor fundamental quantities (like Drag, max pressure, min pressure) to make sure they are converged. These can be found under Solve->Monitors. You can decrease the limit for the residual convergence by going to Solve->Monitors->Residuals.

Other things to watch out for: Make sure you've set your reference values (Report->Reference Values). Check the quality of your mesh in Gambit (or whatever meshing program you use) to make sure that you're skewness is low. And make sure that you're refined enough around the sphere (several cells within the boundary layer... do planar cuts through the geometry in Fluent and look at the BL).

Hope this helps, and good luck, Jason

one question: is it laminar or turbulent flow?

have you used a steady solver?

my blog: http://richard001.blogspot.com/

its laminar and unsteadt model, if possible can u look at the meshing, is it good or bad i am just a beginer http://www.home.iitk.ac.in/~himan

I can not open your webpage sorry. however, you can just send me it by email.

my blog: http://richard001.blogspot.com/