August 21, 2023 at 6:28 pmsinan ozbolgiliSubscriber
I am trying to simulate boiling around horizontal tube to check bevaiour bubble and find heat flux and boiling heat trasfer coefficinet with different super heat temperature ( super heat = tube wall temp. - water satuation temp.)
I selelcted Eulerian- RPI model with kepsilon model.
Please see which corelation I put for forces, ehat-mass transfer. ( taken from a article already done by soneone for PhD thesis)
Hovever, I am fixing time step as 10^-9 and mesh fisr layer = 10^-5 still havong floated error.
August 22, 2023 at 5:09 am
August 22, 2023 at 10:59 amRobAnsys Employee
If you're setting the wall temperature like that you may be pushing the boiling too quickly: ie the near wall must boil instantly.
Check the purpose of the wall boiling models too, and whether you have too much near wall refinement.
August 22, 2023 at 11:15 am
August 22, 2023 at 11:28 amRobAnsys Employee
I'm not sure what I'm looking at but aim for an aspect ratio of nearer 1 for multiphase. You need to account for the vapour moving along the surface as well as resolving the flow normal to the wall.
August 22, 2023 at 12:16 pmsinan ozbolgiliSubscriber
In this case, the fist layer should be much closeer to wall? Layer groving level should be less ? I mean distance between 1stand 2nd should be considerd as much less?
August 22, 2023 at 12:19 pmRobAnsys Employee
From the image I don't know what your near wall mesh is so can't comment.
August 22, 2023 at 12:36 pm
August 22, 2023 at 1:27 pmRobAnsys Employee
You may want to read up on the boiling model, I suspect the near wall mesh is too fine. Aspect ratio is likely very high for multiphase too.
August 22, 2023 at 1:39 pmsinan ozbolgiliSubscriber
Thanks, do I need to change first layer thinkes to increase and rescrease ratio ?
August 22, 2023 at 1:43 pmRobAnsys Employee
If the mesh is too fine increasing the first cell height might be a good idea! Increasing the number of nodes around the pipe will also help with the aspect ratio.
August 22, 2023 at 1:47 pmsinan ozbolgiliSubscriber
Let me try, thanks
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