I have a case of high pressure steam condensation in a circular c/s tube where complete liquid condensate is observed throughout 70-75% of the tube length from outlet.
Inlet is mass flow rate with initial guess pressure , outlet is pressure outlet with a know experimental value. The tube wall is is at const. temperature, far lower than the saturation temperature.
My problem is my Fluent CFD solution with evapo-conden model, has considerable outlet backflow throughout the calculations.
My question is, if I extend the domain, how can I use the known outlet pressure that I have. That pressure is applicable only to the main domain of interest, isn’t it?
secondly, should I keep the wall boundary condition as the same (temperature) or change it to isothermal (in order to less mess with the artificial domain extension)?
Dear Soumitra,
Usually the backflow happens when the imposed boundary condition is not true can the silver try to change the boundary condition. However, if it a study state problem you can check the run the simulation till the number of iteration where mass flux become steady.
Now you can extend the domain and check if the value of steady mass remain same. If yes, then you can work with smaller domain itself with backflow.
thanks. Now I will check with the mass flux stability.
and yes I am running a steady state simulation, but even with 12000 iterations, the solution did not converge, and the back flow condition has been almost thought the calculations.
Syed Mughees Ali Do you think the backflow warnings could also be affectIngale the convergence?
So even if I extend the domain, as long as backflow is still there (now far from actual smaller domain), it would cause problem towards convergence, is that so?
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