Round jet model in FLUENT
I'm trying to do a turbulent analysis of a simple round jet in Fluent 6.3 and am struggling to get a correct solution. I have tried everything I can think of with no success. The "best" settings I have found so far are below, but I still don't get a self-similar solution.
My control volume looks like this:
The top boundary is set to outflow (I'm using incompressible flow.)
The right boundary is set to outflow.
The bottom boundary is set to an axis (jet centerline).
The left-bottom boundary is set to a velocity inlet (velocity specified such that Re ~ 5000).
The left-top boundary is set to outflow.
The left-middle boundary and all internal boundaries are set to wall (jet wall).
I'm trying to compare the S-A, k-eps, and k-w equations with default constants (none give me a correct solution).
Second-order solvers for pressure and momentum.
SIMPLE solver for pressure-velocity coupling.
My grid is spaced such that I have 20 grid points along the jet radius.
Control volume extends 20 diameters downstream of jet exit and 5 diameters above jet wall.
Any other settings are default.
Any ideas? This is my first real Fluent project, so maybe there's something obvious I'm missing.
Have you tried to turn some of the outflows conditions to wall condition??? Some numerical problem may occur if you use outflow condition in the left-top region, due to recirculation in this zone... Are you trying to correlate those results to some specific paper??? If not, i recommend the paper of Hussain: Velocity measurements in a high-Reynolds-number, momentum-conserving, axisymmetric, turbulent jet...
are you getting an answer at all? This is basically just a flow problem, correct? If you plot the residuals you can see if it is diverging or flat-lining. What is your overall grid count? I would try to mesh it a little finer and see what happens. I do agree with the above post about treating the right upper bc as a wall first. I believe you can post pics on here, so a gambit screen shot might help out too.
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