Does fluent has limits in its computation? Can't get convergence and mass balance with hydrogen flow (mass flow rate 7e-5 kg/s and velocity 0.022 m/s)in transient mode. My model works with 100 times the same mass flow rate. Any idea will be greatly appreciated

describe u physicl model

use double precision if u think it is a prob of ur value too low.

mass is extensve property. unlike the termprature and pressure

please coudl u describe ur problem.i.e physical model, boundary conditions, any assumption. like symetry or periodic

regards

Use double precision solver

My set up is a rectangular configuration with walls everywhere and three windows. One window in the ground is set as mass flow rate, one in the ceiling is a pressure outlet and another one in the front wall as pressure inlet. I am modeling a very simple gas dispersion problem. I am using parallel computers network.

mass flow inlet and pressure inlet and one pressure outlet, ... together they seems to be creating problem ... u might want to consider another combination ..or try increasing number of iterations per time step (they should be quite large to get these together workign well) ...

I changed the mass flow rate to pressure inlet which gives 7.1e-5 Pa at the pressure inlet (5.3e-7 Torr). I don't know if the NS equations still hold at that low pressure.