Dear All,
I need some guidance in solving a CFD problem.
The main problem is that as soon as I run the calculation in Fluent, the solution diverges after 10-20 iterations. The parameters for the solution in Fluent are as follows:
(1) Model - Realizable k-epsilon with NWF
(2) Boundry Conditions - Inlet velocity with turbulence intensity of 1% and viscosity ratio of 10 %
AND
Outlet pressure with turbulence intensity of 5% and viscosity ratio of 10 %
(3) Courant no = 50 with HYBRID initialization
(4) Solution Method -
(a) scheme - coupled
(b) gradient - least square cell based
(c) pressure - second order
(d) momentum - second order
(e) turbulence kinetic energy - second order
(f) turbulence dissipation rate - second order
Any and all help will be highly appreciated
Regards, :)
A few suggestions from looking at your setup:
* Start your simulation with first order schemes for turbulence properties, which should help to stabilize your start-up of the simulation. If the simulation and flow field is well developed, you can still try to switch to full second order approximation, if necesary.
* If you are aiming for doing the simulation as a steady-state solution (i.e. not a transient simulation), than it is today's best practice to switch to the pseudo-transient scheme. I see this toggle deactivated in your setup. By playing with the user defined pseudo-transient time-scale you should be able to run this simulation more numerically stable. At least this is my experience. Without this toggle being switched on (and if this is not a transient simulation), the ANSYS Fluent solver tries to solve the elliptic PDE problem for a steady-state RANS simulation and this might be quite a stiff mathematical problem at the start.
Hopefully this helps.
Regards,
Thomas Frank.
Dear Taha ,
You can also check you mesh scale and choose the correcte rexations factors .
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