[javad2140]

Hi all,
I am working on a flame affected by external magnetic field using MHD module with fluent 14.5 .As the physical domain is attached to the email, the magnetic field is applied to the pressure inlet boundary. My settings are:

Model settings: 2D, k-w SST ,Non-premixed combustion (with 8 species), Magnetic Induction model with under relaxation of 0.6
Boundary conditions: axis,velocity inlet (for fuel), magnetic field applied in x-direction for pressure inlet boundary
Solver: Pressure Coupled

But I got the following error:
# Divergence detected in AMG solver: pressure coupled -> Decreasing coarsening group size!
# Divergence detected in AMG solver: pressure coupled -> Increasing relaxation sweeps!
# Divergence detected in AMG solver: pressure coupled -> Changing to W-cycle!

After the detected error, I used Pseudo Trandient method, but nothing was changed (this method change the cycle type of all the equations to F-Cycle).
I decreased “coarsen by” and increased the pre-sweep for scalar and coupled parameters in advanced solution controls, but the error persist. I also reduced the URF of the pressure,energy,density, fmean, and B_y to 0.1 step by step and I couldn’t fix the problem.
When I used BCGSTAB stabilization method for flow I encountered AMG Divergence for k Equation. As I changed the Stabilization method for k, AMG divergence detected in the next equation. Finally I changed all of the equation to BCGSTAB stabilization method, But immediately all the residual changed to 1.#QNBe+00 and the solution is converged!
I should mention that the combustion with MHD equation was solved without Lorenz Force and Joule Heating, but as I turned on Lorenz force the solution process stopped working (with b_0 Scale factor of 0.1).
When I applied magnetic field for cold flow (combustion model is off), the problem converged without any error. And when I turned off magnetic problem the combustion is converged. In other word, But I cannot combine both of them.

Thank you in advance for your help.