Hi Everyone, I just wanted to say thank you to those of you who noticed the sign errors on Slides 6 and 7. The coefficients A21 and A23 should be - k L / Delta x. In general for the Laplacian operator, the coefficient of the diagonal (A22) should equal -1 times the sum of the other coefficients, and so the coefficients A21 and A23 should have a - sign! In Equation 1 and 2, Qsource should be negative, as the sign convention here is positive heat fluxes denote heat leaving the cell (so Qsource should be -Qsource as heat is entering the cell). For those of you who support the channel on Patreon, the PDF slides have been corrected there. For everyone else, I have pinned this post so that you are aware of the typos if you go through the derivation in your own work. Thanks again for watching the lectures and supporting the channel :) Aidan
I hope youtube provides a way to re-upload with corrections in slides to the video in a much quicker way. It helps everyone. This is because not everyone sees both videos and comments. @Aidan: It may help everyone.
Yes, me too! I haven't found a better way of doing this yet. It would be really good if there was a way of having a 'living lecture' that we can update with corrections and improvements. The best I can think of so far is to pin a comment with corrections / include the corrections in the description
@@fluidmechanics101 Hello there, I think that the explanation stated above could be rather misleading for someone. There are strict rules that should be followed during the calculation procedure. First, we need to specify a positive direction for the heat flux (let´s assume a positive direction for heat flowing INTO the element). Therefore, any heat flowing out of the element will have a minus sign. Then, we need to stick to the second rule which is the fact that heat flows from a higher temperature to a lower one. So, according to our specified diagram, the temperature differences should always be written as follows: (temperature at the tail of the arrow - temperature at the head of the arrow). The trick is that we can specify the directions of the arrows in the diagram arbitrarily as long as we stick to these rules. Hope it helps! Thanks for the great work!
It’s just great to see how you manage to unfold the less intuitive concepts into a super clear explanation based on understanding rather than learning definitions by heart. Keep it up man!
Your mastery over the topic is so great that everything challenging about CFD becomes easy to grasp thanks to your beautifully chosen examples during the lecture.
Hello from Russia. it's really cool that you record such informative and explanatory videos, thank you very much, I really want you to release your videos more often, as they help to better understand the work of cfd code. I'm really looking forward to the second part about the residuals. thank you!
Good grief! What a perfectly wonderful explanatory video. After four years of engineering I didn't get it half as well as I got it from your presentation. Thank you!
This is great! Finally residuals are being addressed..went through some cfd manuals but there was never really a clear explanation about what or how..thanks for the awesome video. Can't wait to see the next one
Very good talk, and well explained. I like the physical intuition, it is exactly the way I interpret residuals as well. For a typical incompressible solver, the residual normally represents how 'divergence free' your flow is. For our code, we actually use both L_2 and L_inf and have relations between them to assess convergence. I am sure you will touch on this in the next parts but felt I would just add the below: Another added approach I have seen to residual normals is volume weighting. Here, every cell's residual is multiplied by the volume of the cell, and then the domain volume is divided through instead of N. This allows for small stiff cells to not hold up a simulation. This can be useful on unstructured meshes. Yet another thing to do is to divide your residual by b, this normalises the residual in a way that makes the problem less dependent on the dimensionality of the simulation. In this case, the interpretation is more along the lines of how many orders do you want to drop the residual 'relative to the starting point'. This can provide more consistent convergence tolerances being applied.
Thank you so much for the explanation. I'm used to follow what my lecturer does since he doesn't explain anything abt residual concept. Now I really understand it after watching this vid. Looking forward for Part II. Keep it up man!
Eagerly waiting and excited to hear your talks they are great and help me out very much in my masters studies it an request can you please make some video on Aeroacoustics cfd simulation basics
Your lucid way of explanation is just awesome. When I have question like how can I get just a value for the residual that may represent residuals of each cells.? And there you explain. I do not even recognise that the video has ended. Thank you so much for your hardwork.
Thanks Man for the informative work, this kind of work over youtube may not be benifitial to you compared to the youtubers who provide silly content but, the gold stays gold and whatever else is whatever else. keep the good work up, we are excited for more !
Q: In practice, what do you think is the acceptable range of representative residual values to say that you have good results in your CFD? Some papers say around 10^-4 and below for all transport parameters. Can't wait for the next parts of your lecture.
Yes, 10^-4 seems to be pretty good in most CFD solvers (just from personal experience and the experience of others). But as always ... please check other quantities to check you have convergence (forces, moments, point monitors etc). Residuals are not enough by themselves!
Wallahi this guy explains things really well! He is a master! Please consider explaining the difference in using fvSolution in openfoam, which is faster GMAC or PCG solvers, smoothers and those complicated topics 😭
It’s just disappointing, that there are not all parts of your already out! Awesome how easy cou can deliver that complicated stuff in an easy manner. Thanks a lot!
As usual, great content! Thank you a lot, I’m a CFD user but thanks to you I’ve been building up some of the concepts that always slipped away from my understanding.
Thanks for this amazing video. Residuals topic can be very confusing at times and it’s difficult to interpret the residual line plots. Eagerly looking forward for the subsequent parts. Also it would be helpful if you could address oscillating residual plots which I had once encountered in my CFD simulation.
Just a few days back was researching the residual outputs from solvers in OF! Thank you. Can you please also consider making videos on linear solvers and compressible solves.
Thank you for these lectures once again, you are such a good pedagog on this subject! There is a slight error on the slide at 4:15 where you go through the numerical calculation. The T2 term should be negative overall, following all the algebra.
![[CFD] Residuals in CFD (Part 2) - Scaling](http://i.ytimg.com/vi/YXElSo3Zdzk/mqdefault.jpg)
![[CFD] Residuals in CFD (Part 2) - Scaling](/img/tr.png)
![[CFD] How Fine should my CFD mesh be?](http://i.ytimg.com/vi/60fDz2cVdy8/mqdefault.jpg)
![[CFD] The Courant (CFL) Number](/img/n.gif)
Hi Everyone, I just wanted to say thank you to those of you who noticed the sign errors on Slides 6 and 7. The coefficients A21 and A23 should be - k L / Delta x. In general for the Laplacian operator, the coefficient of the diagonal (A22) should equal -1 times the sum of the other coefficients, and so the coefficients A21 and A23 should have a - sign! In Equation 1 and 2, Qsource should be negative, as the sign convention here is positive heat fluxes denote heat leaving the cell (so Qsource should be -Qsource as heat is entering the cell). For those of you who support the channel on Patreon, the PDF slides have been corrected there. For everyone else, I have pinned this post so that you are aware of the typos if you go through the derivation in your own work. Thanks again for watching the lectures and supporting the channel :) Aidan
can you make how to study transient residuals? big thank you . you are doing great work sir
I hope youtube provides a way to re-upload with corrections in slides to the video in a much quicker way. It helps everyone. This is because not everyone sees both videos and comments. @Aidan: It may help everyone.
Yes, me too! I haven't found a better way of doing this yet. It would be really good if there was a way of having a 'living lecture' that we can update with corrections and improvements. The best I can think of so far is to pin a comment with corrections / include the corrections in the description
@@fluidmechanics101 Hello there, I think that the explanation stated above could be rather misleading for someone. There are strict rules that should be followed during the calculation procedure. First, we need to specify a positive direction for the heat flux (let´s assume a positive direction for heat flowing INTO the element). Therefore, any heat flowing out of the element will have a minus sign. Then, we need to stick to the second rule which is the fact that heat flows from a higher temperature to a lower one. So, according to our specified diagram, the temperature differences should always be written as follows: (temperature at the tail of the arrow - temperature at the head of the arrow). The trick is that we can specify the directions of the arrows in the diagram arbitrarily as long as we stick to these rules. Hope it helps! Thanks for the great work!
Sir were can I get 3d navier stock equations in python
It’s just great to see how you manage to unfold the less intuitive concepts into a super clear explanation based on understanding rather than learning definitions by heart. Keep it up man!
Your mastery over the topic is so great that everything challenging about CFD becomes easy to grasp thanks to your beautifully chosen examples during the lecture.
You r my new cfd mentor.
I give you the Nobel of engineering on behalf of the CFD community. Respect!
Super clear explanation! Congrats for bring to us a very useful topic in an easyful manner.
What a great video!!! We brazillians are gratefully with your great explanation about residuals in CFD simulation with a clarify inglish.
Hello from Russia. it's really cool that you record such informative and explanatory videos, thank you very much, I really want you to release your videos more often, as they help to better understand the work of cfd code. I'm really looking forward to the second part about the residuals. thank you!
You are the best thing happened to CFD guys. Thanks a lot!
Amazing lecture. Now I am able to understand what residual actually is. Thanks a lot for such a wonderful talk.
Good grief! What a perfectly wonderful explanatory video. After four years of engineering I didn't get it half as well as I got it from your presentation. Thank you!
Another amazing video! The way you explain the equations is truly impressive, making them easy to remember.
Really enjoying the talks on the slightly deeper theory behind the more general CFD concepts that people run into!
Awesome video buddy! You break down super complex concepts into easy-understanding, bearable videos! Keep it up.
This is great! Finally residuals are being addressed..went through some cfd manuals but there was never really a clear explanation about what or how..thanks for the awesome video. Can't wait to see the next one
Great video! I've never seen any other media(clip, text, manual, whatever) describing the basics of residuals as much as this.
Thanks a lot Aidan. I really enjoyed the whole series. It really explains all the important nuisances one needs to know. Great work.
your crystal clear explanation just saved my day! thank you so much for the effort! :D
Very good talk, and well explained. I like the physical intuition, it is exactly the way I interpret residuals as well. For a typical incompressible solver, the residual normally represents how 'divergence free' your flow is. For our code, we actually use both L_2 and L_inf and have relations between them to assess convergence.
I am sure you will touch on this in the next parts but felt I would just add the below:
Another added approach I have seen to residual normals is volume weighting. Here, every cell's residual is multiplied by the volume of the cell, and then the domain volume is divided through instead of N. This allows for small stiff cells to not hold up a simulation. This can be useful on unstructured meshes.
Yet another thing to do is to divide your residual by b, this normalises the residual in a way that makes the problem less dependent on the dimensionality of the simulation. In this case, the interpretation is more along the lines of how many orders do you want to drop the residual 'relative to the starting point'. This can provide more consistent convergence tolerances being applied.
Best explanation I have seen on this; thank you so much!
Many thanks for your detailed clarifications. Excited to watch the next part.
Just a few words. Simply the best explanation I have ever heard! Thank you very much!
Brilliant how you chose a simple heat conduction problem to explain residuals. Excellent talk. Look forward to the next in the series
Not only useful, extremely useful.
Thanks a lot. It’s just very impressive. can't wait watching part 2 3 and 4!
And 5, 6 and 7
Its is very good that someone can simplfy the complex information and present in a beautiful way .
Great video!! Your breakdowns are extremely easy to understand and implement!
Very helpful! I have been waiting for you to make videos on residuals! Looking forward to the next videos!
clear, concise explantion. Looking forward for the next ones.
It was a great talk indeed. Can't wait for the next parts.
Thanks for this helpful video. Excited about the other parts!
Terrific presentation, great visuals and excellent pace. Big thumbs up!
Great video (part 1). Looking forward eagerly to the coming parts.
Thank you so much for such a detailed and perfect explanation!
thank you ,you are great
Thank you so much for the explanation. Eagerly waiting for part II. Keep it up!
Well organized and explained deeply. Thanks a lot.
Thanks Aidan, I've really enjoyed it and found it quite useful.
What a wonderful and beautifully simple explanation! Thank you, sincerely!
Eagerly awaiting for the next parts.
Great! It really helps to have a good understanding of what residuals mean! Thanks!
Excellent explanation loved it
This video made me feel just WOW!
Great explanation sir.
Loved it!!
I found this video very helpfull and got more understanding in that resudials mean. Going to part 2.
As always thanks a lot for such a detailed explanation on residuals. Looking forward to learn more on this.
Great explanation!! Looking forward to many such talks.
Excelente lecture. Waiting for next videos.
Fantastic explanation of residuals. I finally know what Φ represents. I can't wait for your residual scaling explanation (local v global)
Very useful video. Cleared all concepts for me.
awesome video couldn't have explained it better
it was very useful to understand the behavior of residuals during execution
This is exactly what I needed! Thanks
So enlightening talk and thank you very much
Thanks, Aidan, for your brilliant explanation on the practice residuals! It really helps me to understand the part of CFD!
Thanks a lot, Aidan! It's a perfect explanation
Thanks for making such a brilliant video
Thank you so much for the explanation. I'm used to follow what my lecturer does since he doesn't explain anything abt residual concept. Now I really understand it after watching this vid. Looking forward for Part II. Keep it up man!
u are just a god! Thank you for a such incredible explanation of a not so homogen information in different sources!
Eagerly waiting and excited to hear your talks they are great and help me out very much in my masters studies it an request can you please make some video on Aeroacoustics cfd simulation basics
Very good talk, and well explained. Thank you.
Your lucid way of explanation is just awesome.
When I have question like how can I get just a value for the residual that may represent residuals of each cells.? And there you explain.
I do not even recognise that the video has ended.
Thank you so much for your hardwork.
That is Great Mate, really helpful cheers!
thanks a lot for these valuable lessons ..
its good to be back here learning basics of CFD, always the best and informative videos.
thanks
excellent video! so easy to understand! thanks so much for all your videos :)
Thank You Sir i finally understood what is all about. You are supertalended teacher!
Excellent talk!!!
Thanks Man for the informative work, this kind of work over youtube may not be benifitial to you compared to the youtubers who provide silly content but, the gold stays gold and whatever else is whatever else. keep the good work up, we are excited for more !
Thank you so much, I really appreciate it
Thanks for sharing! Great explanation. 🙂
Great explanation...thank you.
I found that video series really useful ,and what I would say is I have better understanding of residual plots and convergence process :)
Thanks
Fantastic!
I really really appreciate your videos, these are so informative and very very helpful
Fantastic 🙂 I'm glad you are finding them useful
Amazingly explained, thank you
Nicely Explained. Thanks for such informative video.
Q: In practice, what do you think is the acceptable range of representative residual values to say that you have good results in your CFD? Some papers say around 10^-4 and below for all transport parameters.
Can't wait for the next parts of your lecture.
Yes, 10^-4 seems to be pretty good in most CFD solvers (just from personal experience and the experience of others). But as always ... please check other quantities to check you have convergence (forces, moments, point monitors etc). Residuals are not enough by themselves!
Thank You so much for this wonderful and beautifully simple explanation, Thank you, sincerely!
Wallahi this guy explains things really well! He is a master! Please consider explaining the difference in using fvSolution in openfoam, which is faster GMAC or PCG solvers, smoothers and those complicated topics 😭
Спасибо! Жду следующее видео!
Beautifully structured presentation! Thank you so much!
YOU "R" A LIFESAVER. Thank you so much.
Fantastic lecture, many thanks.
Great video! Thank you very much for sharing this!
Thanks very much. The videos are very helpful.
It’s just disappointing, that there are not all parts of your already out! Awesome how easy cou can deliver that complicated stuff in an easy manner. Thanks a lot!
Thank you very much for the explanation! 👍
Fantastic video! Really helped me in better understanding those funny wobbly lines 😁
Thsnk you, please continue the topic
i love it, great work
Great work!
Great presentation! I appreciate for putting in so much effort. Thank you!
As usual, great content! Thank you a lot, I’m a CFD user but thanks to you I’ve been building up some of the concepts that always slipped away from my understanding.
Thanks for this amazing video. Residuals topic can be very confusing at times and it’s difficult to interpret the residual line plots.
Eagerly looking forward for the subsequent parts.
Also it would be helpful if you could address oscillating residual plots which I had once encountered in my CFD simulation.
Great explanation Bro…
thanks a lot for sharing your knowledge, I hope to see next videos soon.
Thank you very much for all you taught me!
great video as always!
Mauro
Thanks Mauro 🙂
this video is exactly what I want
Great video! Thank you!
Just a few days back was researching the residual outputs from solvers in OF! Thank you. Can you please also consider making videos on linear solvers and compressible solves.
Thank you for these lectures once again, you are such a good pedagog on this subject! There is a slight error on the slide at 4:15 where you go through the numerical calculation. The T2 term should be negative overall, following all the algebra.
... ahh a typo. Thanks for spotting!
Great! Really helpful!