[CAP_NJ]

Dear all,
I have simulated a ducted fan config (see figure) with CFX AND Fluent with the same boundary conditions - pt Inlet and p Outlet and the same RPM. I have used the default turbulence settings etc. in both cases, hence they differ slighlty to each other. However, when I am calculating the overall force (thrust) in z direction I get significantly different results for both solvers. I am aware of the importance in setting the reference pressure in Fluent correctly, since it is sensitive to the results (see second equation). I dont get the advantage of relating the pressure to a reference pressure (why is it reducing round off errors). As far as I know, CFX is estimating the force by the accumulation of pressure and viscous force on each surface but I couldnt find any mathematical definition in user guides. In Fluent I get -212N and in CFX -68N which means the force in cfx is only about a third as high as the one calculated in fluent. Even when I include the reference pressure in CFX as done in fluent, the result is completely different (changing from -68N to +266.25N). I dont think the difference can be explained by the differences in turbulence settings (while both are using SST) etc. Do you know where the difference comes from??? I am really grateful for every help you can provide!!!