[CFD] Relaxation in CFD (Part 2) - Implicit Relaxation, Diagonal Dominance

  Рет қаралды 9,173

Fluid Mechanics 101

Fluid Mechanics 101

Күн бұрын

An introduction to relaxation and how it can be used to help improve convergence in CFD.
Time stamps:
0:00 Introduction
0:48 Recap
3:52 Implicit Relaxation
7:12 Compact Form
9:16 Explicit vs Implicit
10:25 Mathematical Derivation
12:46 Formula Comparison
15:43 Matrix Form
17: 24 Diagonal Dominance
22:58 History
24:30 OpenFOAM (fvSolution)
28:30 Summary
29:28 Outro
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Some useful references
============================================
1. Ferziger & Peric, 'Computational Methods for Fluid Dynamics', 3rd Edition, Springer-Verlag, Berlin, Heidelberg, New York, 2002.
www.amazon.co.uk/Computationa... [Page 118, 149]
2. S. Patankar, 'Numerical Heat Transfer and Fluid Flow', 1st Edition, McGraw-Hill, 1980. [Page 67]
2. ANSYS Fluent 12.0 User manual (18.4.4 Steady-State Iterative Algorithm)
www.afs.enea.it/project/neptu...
3. OpenFOAM: User Guide v2012. Under relaxation
www.openfoam.com/documentatio...
============================================
Want to learn more?
============================================
Grab a copy of my CFD Fundamentals Course (for beginners):
www.udemy.com/course/computat...
Learn how to write your own CFD code in MATLAB and python (for intermediates):
dr-aidan-wimshurst-s-school.t...
Learn how I draw my figures and diagrams in Inkscape (for everyone):
dr-aidan-wimshurst-s-school.t...
============================================
Did you like the video?
============================================
Download the lecture slides from my website:
www.fluidmechanics101.com/pag...
Buy me a coffee to say thanks:
www.buymeacoffee.com/NKEZrhvg0
Support the channel on Patreon (and get useful extras for your CFD studies):
/ fluidmechanics101
============================================
Donations:
============================================
1) PayPal
www.paypal.me/fluidmechanics101
==================================
Disclaimer
==================================
The methods, algorithms, equations, formulae, diagrams and explanations in this talk are for educational and demonstrative purposes only. They should never be used to analyse, design, accredit or validate real scientific / engineering / mathematical structures and flow systems. For such applications, appropriate trained, qualified and accredited (SQEP) engineers / scientists should be consulted along with the appropriate documentation, procedures and engineering standards. Furthermore, the information contained within this talk has not been verified, peer reviewed or checked in any way and is likely to contain several errors. It is therefore not appropriate to use this talk itself (or any of the algorithms, equations, formulae, diagrams and explanations contained within this talk) as an academic or technical reference. The reader should consult the original references and follow the verification and validation processes adopted by your company / institution when carrying out engineering calculations and analyses. Fluid Mechanics 101 and Dr. Aidan Wimshurst are not accountable or liable in any form for the use or misuse of the information contained in this talk beyond the specific educational and demonstrative purposes for which it was intended.

Пікірлер: 37
@somdebsar7378
@somdebsar7378 Ай бұрын
You are just awesome Sir, I really love learning your lectures Sir, you are the BEST!!!
@chinmayarajath829
@chinmayarajath829 Жыл бұрын
Great lecture. Love the emphasis on information relevant to CFD users. Makes it easier to digest
@jk463
@jk463 2 жыл бұрын
Really looking forward to the next part - the terms of steady, transient, and pseudo-transient are quite vague to novices, especially when there is no sufficient guidance. I stand by what I've commented for the talk about residuals - this channel should be officially recommended for CFD newbies in CFD software manuals and universities.
@fluidmechanics101
@fluidmechanics101 2 жыл бұрын
Yes! I am planning to clear all of this up by the end of the series
@mohame.k5399
@mohame.k5399 Жыл бұрын
i totally agree
@ramkumars2329
@ramkumars2329 2 жыл бұрын
nice explanations!, i like the OpenFOAM details that u give in ur talks.. please keep doing good work.. thanks!
@joneidhasannejad6652
@joneidhasannejad6652 2 жыл бұрын
Enjoyed as always!
@ankitsinghbhadouriya5801
@ankitsinghbhadouriya5801 2 жыл бұрын
Interesting video series. 100% for the explanations. Keep doing good work. Thanks. ☺️👍
@morpheus-caffeine
@morpheus-caffeine 10 ай бұрын
Absolutely brilliant video. congrats.
@jimeshpitroda937
@jimeshpitroda937 2 жыл бұрын
Amazing lecture. big thank you.
@HariNarayanaDasari
@HariNarayanaDasari 2 жыл бұрын
Waiting for it, thank you
@mohame.k5399
@mohame.k5399 Жыл бұрын
Great lecture , you have all my gratitude
@yavuzaks1348
@yavuzaks1348 2 жыл бұрын
Very informative. Thanks.
@chinmayakumar5572
@chinmayakumar5572 Жыл бұрын
Excellent inputs
@Mr230306
@Mr230306 2 жыл бұрын
thank you for very informative talk.
@rahuljws7090
@rahuljws7090 2 жыл бұрын
Please open those private videos as well. Your videos are very informative. Thanks
@sureshnonis1314
@sureshnonis1314 2 жыл бұрын
you are doing a great job. I never have found u tube channel like this. You explain very well. If you can explain photoacoustic waves and governing physics equations regarding photoacoustic and how photoacoustic effect relates to CFD, I appreciate it a lot..
@tatipallisateesh8994
@tatipallisateesh8994 2 жыл бұрын
Feels like knowed nice concepts
@SweKelt
@SweKelt 2 жыл бұрын
Thank you! Looking forward to the next part in the series. I can get any run to converge by reducing the pseudo time step Courant number to around 0.1 and using SIMPLEC solver. I wonder why and if the results are accurate
@hardiksharda9673
@hardiksharda9673 Жыл бұрын
From what I have understood, Explicit Relaxation is applied to the field (updated) value after they are solved using the conventional AT=B matrix equation. Implicit Relaxation are directly applied to the conventional AT=B equation. Please Dr. Aiden correct me if I am wrong. Thanks again for your efforts!! 😃
@fluidmechanics101
@fluidmechanics101 Жыл бұрын
Yes! Exactly correct
@hardiksharda9673
@hardiksharda9673 Жыл бұрын
@@fluidmechanics101 Thank You!
@nagarajanp6510
@nagarajanp6510 2 жыл бұрын
sir, im waiting for ur species transportation lectures...
@jasonchu852
@jasonchu852 Жыл бұрын
👍
@cwong9241
@cwong9241 Жыл бұрын
Thank you for the fantastic lecture. Could I please ask is it rare to use very small URF for example 0.01 to solve the problem? I am having convergence difficulties in solving swirling flow, after your lecture, I am thinking to try very small URF to stabilise the simulation as swirling is unsteady phenomenon in nature. Could you please advise a little bit on this? Many thanks in advance.
@fluidmechanics101
@fluidmechanics101 Жыл бұрын
Probably better to go with a transient solver 👍
@ishannande7763
@ishannande7763 2 жыл бұрын
This is a really good video. On a side note, are there any textbooks that you can recommend for studying vector calculus and linear algebra? There are engineering textbooks and then there are textbooks that are relevant to CFD research. Have you come across any such textbooks ?
@fluidmechanics101
@fluidmechanics101 2 жыл бұрын
For linear algebra the book by Saad 'iterative methods for sparse linear systems' is really good and it's free! Just give a Google search and you should find it. Sadly I don't have anything good for vector calculus. The OpenFoam manuals are pretty good for vector calculus that is related to CFD
@ishannande7763
@ishannande7763 2 жыл бұрын
@@fluidmechanics101 Thank you.
@TeeTeeNet
@TeeTeeNet 2 жыл бұрын
There’s also Moukalled, Mangani & Darwish (2016): antivirus.uclv.edu.cu/update/libros/Engineering/The%20Finite%20Volume%20Method%20in%20Computational%20Fluid%20Dynamics%20-%20F.%20Moukalled%2C%20L.%20Mangani%2C%20M.%20Darwish%2C%201st%20ed.%202016%20-%20978-3-319-16874-6.pdf
@mercurial152
@mercurial152 2 жыл бұрын
Thanks for ur explanation. Do u know about high order relaxation ? Fluent said it is used for additional term in high order term, but in the formulation, they use phi intermediate instead of phi calc. I don't know what is phi intermediate, can u explain ? thanks
@fluidmechanics101
@fluidmechanics101 2 жыл бұрын
Not sure. If the manual doesn't say then I guess we will never know! (Unless we could read the mind of ANSYS 😅)
@mercurial152
@mercurial152 2 жыл бұрын
@@fluidmechanics101 I think it's the same as phi calc :) but i'm not sure, haha
@xinyunliu969
@xinyunliu969 2 жыл бұрын
I have a question. It seems that set alpha to 1 is the same as the unrelaxation case. However, in my interFoam case, setting alpha to 1 a converge is achieved, but deleting the relaxationFactors in fvSolution leads to a divergence. How to explain this? Thanks!
@fluidmechanics101
@fluidmechanics101 2 жыл бұрын
I am not too familiar with interFoam but simpleFoam definitely needs relaxation factors less than 1!
@xinyunliu969
@xinyunliu969 2 жыл бұрын
I read the OpenFoam UserGuide: alpha = 1 leads to guaranteed matrix diagonal equality/dominance. It seems that in that case the relaxation algorithm still does something?
@fluidmechanics101
@fluidmechanics101 2 жыл бұрын
Ahhh ok, I think the latest versions of OpenFOAM may have changed what 'alpha' actually does. I will need to have a read of this
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