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"steady/repeat periodic flow" from transient simulation for multiphase flow ? |
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LYH
Join Date: Dec 2023
Posts: 11
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I am running 2-pahse flow simulation using ansys fluent.
I tried both steady and transient setting. 1. Transient After several trials, I set the transient simulation as follow: For "Fixed" type Number of time steps: 2e5 Time step size: 1.25e-6s Max iterations per time step: 25 At the same time I run "Adaptive" type : Number of time steps: 2e5 Initial time step size: 1.25e-6s Number of fixed time step: 1s Minimum time step size: 1e-8s Maximum time step size: 1s Max iterations per time step: 100 2. Steady Cannot converge unless time-step size set smaller than 1e-10, which is nmearly impossible for me to run in such slow computing. From the volume fraction results, I observed that the flow seem to have "pseudo repetition pattern" at certain period of time. But it may not occur constantly and frequently My question are : 1. How to determine transient simulation has reached "steady, no change over time" or "pattern over a length of time repeating unconstantly over period" ? 2. Where it starts / How long the 'length of time' that recurring pattern occurs ? 3. How to verify that the "steady/repeat periodic flow" are enough to descirbe the case ? 4. Is there any other way to speed up the calculation process (eg: set time step size much bigger than 1.25e-6, set higher tolerance? but able to converge)? Any suggestion are welcome. Thank you in advance. View my previous replies: Transient simulation -> Steady state solution |
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