CFD Online Logo CFD Online URL
Home > Forums > General Forums > Main CFD Forum

No under-relaxation in passive scalar

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Search this Thread Display Modes
Old   July 23, 2020, 13:12
Question No under-relaxation in passive scalar
New Member
Join Date: Jul 2020
Posts: 1
Rep Power: 0
jose_prime is on a distinguished road

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.
jose_prime is offline   Reply With Quote


passive scalar, under-relaxation factor

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
problem during mpi in server: expected Scalar, found on line 0 the word 'nan' muth OpenFOAM Running, Solving & CFD 3 August 27, 2018 04:18
Division by zero exception - loop over scalarField Pat84 OpenFOAM Programming & Development 6 February 18, 2017 05:57
Issue symmetryPlane 2.5d extruded airfoil simulation 281419 OpenFOAM Running, Solving & CFD 5 November 28, 2015 13:09
Diverging solution in transonicMRFDyMFoam tsalter OpenFOAM Running, Solving & CFD 30 July 7, 2014 06:20
compressible flow in turbocharger riesotto OpenFOAM 50 May 26, 2014 01:47

All times are GMT -4. The time now is 15:35.