I am simulating Heat Exchanger. I have tried and tested all the methods to resolve this issue from the internet like refining mesh, improving skewness and orthogonal quality ,extending outlet to further downstream, adjust relaxation factors, adapt iso-value, avoid sharp edges for to abstain from discontinuity, but still encountering reverse flow.
Now what I think is that reverse flow is due to the fact that pressure at the outlet is 1atm which is our outlet boundary condition and it seems pressure somewhere inside domain is lesser due to which flow is trying to re-enter the domain since we know Flow of a fluid is from high pressure to low pressure. so for its remedy i should decrease the outlet pressure from 1 atm to a lit bit lower to encounter the reverse flow? would this technique work?
Muhammed; Your question reminds me of my strong force hydraulic analogue where positron pressure escapes thru a neutron’s low down quark pressure outlets allowing the protons to thrust together. When they are too close the outlets choke with back pressure leaving the protons suspended vibrating between in-push and back-push.
https://www.yowahbooks.com/home/strong-force-hydraulic-analogue/
Hi Muhammad,
You could tackle the issue of reverse flow at outlet by two ways:
(1) Increase the domain at the outlet, so that the location of reverse flow is moved to a location further from the area of interest.
(2) If you are dealing with incompressible ideal gas flow, then you could increase the pressure at the outlet to a higher value. This will not effect the final results as incompressible ideal gas formulation works based on pressure difference and not the pressure value by itself.
Hope it helps!
Regards,
Rajesh.
Dear Muhammad,
I agree with Rajesh comment (1). But please mention that the reverse flow is the real phenomena such as at the back region of the cylinder. Instead, if the real situation has no such back flow, then you have to extend the distance from the last object you simulate and the outlet position. In Ansys Fluent 2020 there is an option to avoid the back flow.
Regards,
Nazar
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