Hi I am solving oil combustion problem on CFX 5.7, in which I am facing problem of convergence.

a. I started with a timescale of 5 e-3, but problem was not converging even after 970 iterations.

b. I tried to keep a timescale of 1e-3, but mass and momentum residuals showed oscillations, so stopped solver.

c. I restarted the problem with timescale of 1e-3 for mass fractions and 5e-3 for global model. But still the convergence rate is very slow.

Can somebody suggest me some tips to improve the convergence in oil combustion or combustion related problems Thanks Krishnarao

Try lovering time step and then increase when runing...Sometimes the time step could be as low as 1e-8 [s]