# About the differences in results obtained from CFX and Fluent

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 December 23, 2023, 07:06 About the differences in results obtained from CFX and Fluent #1 New Member   Ali Can Join Date: Apr 2021 Posts: 28 Rep Power: 5 Hello, I am modeling cavity flow via 0.85 Mach and 6.5 million Re conditions. I want to calculate the aerodynamic forces (Fx, Fy, Fz) on the rear wall of the cavity. In this context, I am conducting my studies using both Fluent and CFX. I am using the same mesh for both software. However, the results I obtained with Fluent and CFX are quite different from each other. Where do you think the problem might be? I have specified my boundary conditions below. Fluent Operating pressure = 0 Inlet = pressure far field, 0.85 Mach, gauge pressure = 50000 Pa Outlet = pressure far field, 0.85 Mach, gauge pressure = 50000 Pa Second order discretization schemes Ideal gas SST k-w turbulence model CFX Reference Pressure = 0 Inlet = Inlet boundary condition-subsonic and velocity components are identified Outlet = Outlet boundary condition – subsonic- averaged pressure/static pressure = 50000 Pa (I tried both) Second order discretization schemes Ideal gas Shear Stress Transport model I suspect that the issue lies in the definition of boundary or initial conditions, but I have not yet been able to pinpoint where the problem is. Thank you, Ryuzaki. Last edited by Ryuzaki; December 23, 2023 at 14:16.

 December 23, 2023, 15:54 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,748 Rep Power: 143 Please show an image of what you are modelling and an image of the differences between your results. But yes, your boundary conditions appear different. At the inlet you are using a pressure bc for the inlet in Fluent but a velocity bc for CFX. At the outlet fluent has constant pressure defined everywhere over the boundary but CFX has an averaged pressure defined - so the pressure can be higher and lower at locations, it is the average which is kept at your defined value. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

 December 27, 2023, 17:40 #3 Senior Member   Join Date: Jun 2009 Posts: 1,825 Rep Power: 33 As Glenn mentioned, you are NOT solving the same problem; therefore, nothing to compare. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.