[saurabh.deshpande88]

Hello everyone,I am doing analysis of flow around a NACA 0008 airfoil. Using gambit and fluent for the purpose.
When i use a coarser mesh (i.e. nodes=1,500) my solution is converging and i am getting the results.
But for a fine mesh (nodes=12,000) even after 1,60,000 iterations my solution is not converging and there is not a slightest sign that it will come down! In fact the "residual vs iterations" curve follows a zig-zag pattern. Why is it so?? please help. thanks..

IMP DATA:

residual: 1e-06

inviscid flow, angle of attack=20 degree

Discretization schemes: pressure= presto
momentum= second order upwind

Pressure velocity coupling: simple

underrelaxation factors have been reduced to the extent of 0.01 for pressure and momentum.