Learning Forum

[yangyee]

Hi, everyone,

When I conduct a turbomachinery simulation with URANS or SRS-type method in ANSYS CFX, the residuals of the unsteady simulation are relatively higher than the corresponding steady case, which is used to initialize the flow field. The boundary condition and the discrete scheme for turbulence and convection term keep same between the steady and unsteady simulation. The physical time step(almost 1e-6s) I used is also enough because CFX is an implicit solver. Can anybody tell me the reason? Thank you in advance!

[Surya Deb]

Hello,
How many iterations per time step do you test for the transient solver?
What happens if you increase this number? Do you see a reduction in the residual?
Also for transient solution, it is important to make sure that the residuals converge properly at each time step.
Regards SD