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#1 |
New Member
Jose
Join Date: Jul 2020
Posts: 1
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Hello!
I have a doubt about the need to use under-relaxation. My currently project simulations consist in two steps: 1. Solve flow field. 2. Freeze the flow field and run the transport of a passive scalar (the passive scalar does not run during step 1). In this step, I monitor an average that should converge to a theoretical value. In the first simulation, I set no under-relaxation to the passive scalar (factor = 1) and I was happy with the results. Here is why: 1. The passive scalar is running alone, so it does not affect anything else. 2. The passive scalar residual reduced smoothly without instabilities or oscillations. 3. The value that I monitor converged to the theoretical value smoothly without any instabilities or oscillations. However, I was commanded to introduce under-relaxation in the passive scalar and the justification I was told was "not to rush the solution". I got sincerely puzzled by this, as do not understand this approach. So I have two questions: 1. Aren't my reasons enough to support the decision not to use any under-relaxation? What am I missing about this? Should I be looking into something else? 2. "not to rush the solution"... Shouldn't we try to rush the solutions as long as we do not introduce instabilities in the calculation? Thank you. |
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Tags |
passive scalar, under-relaxation factor |
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