May 12, 2022 at 7:45 amjiangtao.luSubscriber
I am using Euler-Euler model to simulate stirred tank reactors.
At low viscosities (~0.02 [Pa m]), gas holdup is about 0.15, which is normal.
At increased viscosities (~0.08 [Pa m]), with other things unchanged, gas holdup increases to ~0.5, which is quite unreasonable.
Anyone has a clue? Thanks.May 12, 2022 at 8:58 amRobForum ModeratorWhat's the bubble diameter?
May 12, 2022 at 9:21 amjiangtao.luSubscriberThank you Rob for replying. The bubble diameter is 5.5 mm. I expected some increase, but not that large
May 12, 2022 at 10:48 amRobForum ModeratorCan you post some plots? Are you modelling a free surface or using degassing?
May 12, 2022 at 1:39 pmMay 12, 2022 at 1:47 pmRobForum ModeratorYou've lost the free surface too. How does the convergence look as the system looks like it's trying to foam.
May 12, 2022 at 2:02 pmjiangtao.luSubscriberyes, I have the same suspicion as you: foaming. The convergence has no problem, energy dissipation is oscillating as expected.
May 12, 2022 at 3:15 pmRobForum ModeratorHmm. Can you run a couple of time steps with no gas injection and then switch on the gas?
May 13, 2022 at 7:19 amjiangtao.luSubscriberIt is a transient simulation. At beginning it is ok, clear free surface, reasonable gas holdup, just like the left panel. Gradually, it develops into the right panel.
May 13, 2022 at 7:23 amjiangtao.luSubscriberDo you know if FLUENT tested increased viscosities? to which value?
May 13, 2022 at 8:50 amRobForum ModeratorWe did, but not sure on the values - we do run with oil as the carrier phase for pipe flows.
May 13, 2022 at 9:36 amjiangtao.luSubscriberwell, horizontal flow will behave differently from my case for free surface, mixture expansion, etc
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