Fluent Vs Star CCM
 

Hi,.
Anyone can explain me why results from Fluent simulation is little bit difference with Star CCM. For example,result for Drag coefficient, Fluent gives 0.026 and Star CCM gives 0.016. I have try so many times with fluent, and the result still the same. The parameters that i used for both CFD engines are the same (ex:mach no=0.1,surface ref.area and temperature). What i noticed the difference between Fluent and Star CCM is the solver used. fluent used Coupled Explicit and StarCCM used Segregated Solver. Since Fluent also has the Segregated Implicit solver, i have tried running the simulation using this solver and unfortunately the result that i got higher than using Coupled Explicit solver. So, it is because of the solver the result given by Fluent and Star CCM give a bit difference.FYI, this simulation is for UAV aircraft.

You can also compare the STAR-CCM+ Coupled solver to see what happens.
for low Mach number I believe the STAR-CCM+ segregated solver with Ideal gas Model (compressible) can capture what you need much faster then Fluent Coupled solver or Fluent segregated solver with compressibility (guess it is NITA).

Are you using the same mesh for both?

Actually, you need to use couple solver in both simulations to obtain correct solution. Differences that you have looks strange - they are too large. Probably there is convergence problem in CCM or Fluent

Vinicius;
Thank You for your reply,i dont know either STAR CCM have the coupled solver or not since i only have experience with Fluent.Then, for the mesh, in Fluent i used Tetrahedral meshing and in Star CCM with polyhedral meshing.I have no idea why it give very huge different in result, but FYI, in fluent i also doing Grid Indipendent Study range from 300K to 1.5M cells and the result is independent at 0.026.Maybe, i can try your solution.