[CFD] Large Eddy Simulation (LES): An Introduction

[@nikhilverma6457]

That is how one teaches when he knows in and out of the stuff. Best explanation I found till now on internet. Thanks a lot.

[@sramkumar3225]

Key/Important takeaways from this lecture - 1) Eddies and turbulence 2) Wave number representation of an eddy: wavenumber, k=2*pi/d, where d is diameter of the eddy 3) Larger eddies --> greater TKE, lower wavenumber 4) The energy cascade and wave number : the need to resolve atleast 80% of the turbulent kinetic energy (TKE) by a good LES 5) Integral length scale @16:58 (L0) - Single eddy with a length scale (size) that is representative of all levels of eddies present the location of interest 6) @18:10 - Mathematical equation for Integral length scale L0. 7) @19:35 - Use of steady state RANS calculation using any of the standard 2-equation models to determine integral length scale over the domain by post-processing. This forms a preliminary step. 8) @21:59 - Determining an accurate grid size based on the computed length scale. Requires nearly 5*5 cells distributed over a square of size L0*L0 9) Towards 23:40 - new parameter f to replicate the down factor of 5 from the integral scale. Shorter and more efficient way to determine the goodness of the grid resolution is to create parameter f=L0/Delta, where Delta is local cell size. So directly compute f in the initial step of TKE to judge grid.

[@slim590]

Thank you so much

[@ekingorgu]

I asked you to do a video about LES and you delivered! Best YT channel ever.

[@arminkashani5695]

Thank you! This is an absolutely awesome video explaining complex concepts in simple terms. I realized that in the so-called "implicit" LES, as you explained here, the size of mesh dictates how fine we're able to resolve turbulent eddies. This seems to me, as a beginner to LES, to be always true. I would appreciate it if you clarify "implicit" and "explicit" in terms of LES.

[@fluidmechanics101]

Yes you are correct! Explicit LES is more often used in academic studies where a spectral method is used to resolve all the eddies (down to DNS range) and then the filter is applied explicitly on top of this calculation.

[@combustionlab8081]

he is the best teacher for this type of stuff. ıve taken a cfd course in my licence years but it didnt come close to this video in terms of explanations.

[@engineersacademy4137]

Never found an excellent explanation for les than this. Really you are genius and deserve the best

[@user-sz4kh6iq5z]

Wish all teachers were teaching stuff like this man.

[@taohuang5052]

Thank you for such a detailed intro of LES! Hope to watch more lectures on carrying out LES in the future~

[@AshfaqUkulele]

I feel ashamed to watch this genius video without paying for it. You are the Melodysheep of CFD.

[@TheStaticUnit]

Great videos! I just started a research engineer position that's fairly CFD heavy, and your videos are a great refresher!

[@sigmasix09]

The content on this channel so damn academic and wonderful. Thank you so much for your efforts and time and its really helpful for students and inspiring too👏🏼👏🏼👏🏼

[@1321ghost]

What a fantastic lection! I'm just making my master's graduating work and this video is extremely helpful for me. More than that, your English is so clean, that it is pleasure to listen to you. Thank you from Russia!

[@cesaaargm]

I know for sure that those who study turbulence appreciate a lot these videos! thanks!

[@venkatpraveengambhir6196]

Excellent refresher about the concept of LES. Explaining about near-wall effects, and effects of boundary layer inflation and wall mesh sizing on resolving eddies would be even more beneficial. I am in the process of performing a turbomachinery acoustics simulation, and some pointers on those aspects would be mighty helpful.

[@fluidmechanics101]

Yep these will be coming soon. Im going to do the LES videos in stages as there is a lot to cover!

[@shobob29]

Thank you very much for your nice explanation. When I first learnt LES by myself, I couldn’t understand why we have to consider k, but you made it clear. I would like to watch more videos about LES. Every time I watch your video, I get sth new. This is a very precious and exciting opportunity for me.

[@Erickdmartinez]

Would love more videos on LES! Would carry me great through my thesis!

[@randomizer272]

More LES videos pls........ This is a very useful video. thank you.

[@fluidmechanics101]

Yes! More are coming soon 😄

[@ahmhmd1990]

This is not just good for understanding LES, but also provides a good into to turbulence. Well done!

[@anandshankar5127]

Best explanation I found till now on internet. Thanks a lot for your good work

[@refikalpertuncer8512]

Dear Aidan, your channel has by far the greatest chance of becoming the best CFD channel there is. My recommendation is that you should slowly start to include how to implement turbulence models in CFD im terms of coding from simple to relatively complex problems, either here or on your Udemy course. Of course advanced applications should be avoided as it will be very much time consuming on your end, so just enough to give people the main idea. From there you can move forward to heat transfer, combustion, hypersonics etc..however you want. Maybe you can then move to include OpenFOAM or other software. Keep up the great work. Best regards.

[@fluidmechanics101]

Thanks for the advice! I will see what i can do

[@mohammadjadidi233]

Wonderful! I am eagerly waiting for more lectures on LES...

[@nicktrindade]

Best explanation I found till now on internet. Thanks a lot!

[@tejesdas3896]

no comment, only heart felt appreciation for the presentation! thank you so much.

[@ivanpg5091]

Impressed with such a good and practical explanation! I hope you continue with your videos. They are the best on the internet!

[@sigmasix09]

Certainly yes for LES, and the explanation top notch. Thank you so much❤

[@pasansanjeeva3450]

Very good introduction about LES. Waiting for more detailed discussions in the future. Better to have more details and applications of sub-grid scale models in the future.

[@nishchaytiwari8537]

we want more LES videos. Best explaination ever.

[@iloveno3]

Very nice and clear presentation. It was a pleasure to listen to you. Learned lots just in 20 min. Wished i had this at uni.

[@sagark9299]

Thanks a lot for this neatly done introduction to LES. Looking forward to more aspects of LES.

[@ManishSinghPME]

Dear Aidan, Really well-explained video. But I have one point to raise here what you have defined as an integral length scale is actually a turbulent length scale. As mentioned in Appendix A of the paper "Index of Resolution Quality for Large Eddy Simulations".

[@fluidmechanics101]

You may be right. I haven't read that paper

[@janbrychta6278]

Amazing job! The clarity of your explanation is great and really helps to understand the topic. Thanks!

[@PhysicsGoneBad]

Outstanding introduction to LES

[@slim590]

Thank you, please share more on LES

[@adityapahuja3129]

If only i had known it earlier! Kudos on the way you showed the mesh and velocity vector, it cleared the idea so nicely! Please do post more videos❤️

[@tianyiwei8825]

New to LES. Interesting and seems useful and helpful. I am joining a lab where LES is used a lot but now I only have some experience using RANS and honestly speaking not fully understanding the model. I think it would be useful to see this video before going to read some papers about it.

[@lenacaban4178]

Perfect explanation of the LES. Thank you! I'm waiting for more.

[@sunandamedapati4508]

Very helpful explanation. Expecting more videos on LES from your channel..thanks for giving basic and practical idea of LES.

[@keshavkothari5489]

A nicely packed talk, hope more videos may come regarding more intresting topics. I didnt even read RANS ones but the vdo seems well informative

[@jiabaoxing9374]

Thank you so much! Please make more videos on LES! I am so grateful!

[@eslamredalotfy1985]

Very informative and full of LES clues, many thanks

[@velmareddyprudhwidhar7089]

Very helpful...for a beginner like me it's a boon I found this channel

[@saadmansakib01]

The best explanation, hands down! Thank you.

[@Ehsanfarzin-iu9rh]

Many thanks for such a professional teaching. Be successful ...

[@edinmichael4842]

Thanks a lot for doing the talk on LES. Keep doing good. God bless.

[@hafidzazharjakaria2615]

best LES explaination

[@guilherme6535]

Thank you a lot! Your videos are always great and, as a undergraduate in Aerospace Engineering, you make me always want more information! Greetings from Brazil

[@chiragtarsadia8681]

You exactly post the lecture which I was looking for...thank you...and support your work. 😊

[@JB-nd3gk]

It's amazing! You did a good job of explaining the basic concept in LES in the easiest way. Thanks!

[@renethibault2429]

Really nice to watch! Looking forward for more video on this topic. Thank for sharing!

[@behzadlak5002]

Perfect explanation!

[@ricksaylor1953]

Well done! Looking forward to more LES lectures.

[@emiliopelizzari3537]

Thanks for your very usefull and clear explanations

[@abhishekshingala1212]

yes, it is useful and interesting, please don't hesitate to talk about this deeply!!! :)

[@kenaz5985]

Excellent material. Thank you very much

[@MAHM0UDEMAM]

That’s a great discussion. Waiting for the next LES video.

[@omidnazempour4954]

very informative. Thanks a lot.

[@KToMmi]

This is exactly what I was looking for. Wonderfully explained, fantastic job! Thank you!

[@vimalkotak6255]

Simply great again. Thank you very much

[@Martian2023]

really like the style of your lecture

[@rram6062]

Thanks very much for such a nice lecture. It was very informational and helpful. Excellent talk on LES!

[@MrHariPuthar]

Thank you very much. Your videos' likes are almost 10% of the views. That's how helpful your videos are. I hope you have resources to keep up this work. I would be happy to support you on Patreon and I am sure there are lot more who would be willing to.

[@fluidmechanics101]

That would be great! There is a link to my patreon in the video description. I upload all of the lecture slides, courses and templates that i use onto patreon as a small thanks for supporting the channel

[@sauravpathak2116]

Great video Aiden! Love you vidoes. You are helping our community. Appreciate it. Have been familiar with LES theory from Versteeg. The basics are explained well in there too, particularly, about sub grid models; if anyone is interested. However, you wont find stuff about the integral length scale, the practical aspect. Love how you explain stuffs man. Thanks!

[@cfd2050]

Great explanation!

[@jsqueo299]

Awesome video series on LES/turbulence modeling. I learned so much, much more than following along with any textbook or college class- much appreciated! I would love to see future videos on the other sub grid models like dynamic Smagorinsky, one-equation kinetic energy model, etc. and a video that details the governing equations (Filtered Navier Stokes, Favre averaged equations) for explicit and implicit LES would extremely helpful!

[@armo66]

absolutely brilliant!

[@hazemabolholl705]

Think you for this great video. Now I start understanding the concept of LES

[@patelprem695]

You have great knowledge of CFD. I learn too many things from your channel but bit more curious and want to learn Explicit and Implicit solution scheme which is used in Ansys Fluent. Hope you will make a video on it. Thank you.

[@huixu7943]

Great video! Looking forward to the next episode!

[@mdfaiazkhaled1347]

Brilliant work. I wish you good luck.

[@yakovmosseri5818]

Very effective lecture

[@jloudefonty3231]

Great session, thanks

[@ardourmaker]

Let me take a note here, thank you. 19:48 before run LES, a RANS simulation should be run to calculate l0 24:07 If f=l0/delta

[@fluidmechanics101]

Yep 👍 then once you have done the LES you need to check the TKE directly and remesh if necessary

[@junjungarcia7236]

great illustrations and explanation.....

[@sanilgurung1356]

made so much sense !!! thanks a lot

[@unverozkol]

Excellent explanation. Brilliant. Cheers.

[@CRONOSATOME]

Very very useful and benefic!!!

[@princeshapariya]

Thank you Dr. Aidan Wimshurst.

[@RELBELE]

Super useful and very understandable! Great job!

[@venukr937]

Thank you very much Adam

[@aerospaceengineer8484]

Good content Dr., 👏👏

[@pawankumar-ir1fd]

Beautiful

[@ujjwalchetan4907]

It was very useful. Thanks a lot.

[@abhishekbisht3897]

really lucid explanation . can you please upload some content on aeroacoustics as it also does need LES to solve the sound radiated by pressure fluctuation created by those eddies. it will be really helpful

[@princevictorjenneyscharles8643]

Thank you, it is really useful and helpful. Pictorial presentation is really awesome. Expecting more videos from you. :-)

[@Yahyali-b6m]

thanks ver much. very wonderful course.

[@tilakrajpant714]

that was flawless!!

[@bagreeeee8417]

Thank you so much! your video helps me a lot!!!!!!!!!!

[@Aina_MM]

Very useful and interesting, thank you so much!

[@helloworld4476]

Great Video thank you very much! I would very appreciate if you make a video of using the LES for turbomachinery.

[@fluidmechanics101]

There are more LES videos on the way!

[@markoj3512]

Hello Aidan, thank you for the concise explanation about LES. So if a fine proper RANS Simulation is done, a LES Solver with automatic mesh refinement would be very helpful generating a proper mesh for LES. But I'm not sure about the wall treatment in LES, because some RANS-Models use wall function other Models need a resolved boundary layers.

[@fluidmechanics101]

Dont worry, i am going to do a video on this soon. It is more difficult than you might expect because we want to keep the aspect ratio of the cells low, so the boundary layer meshes that we use in RANS arent good enough most of the time unless we use WMLES

[@markoj3512]

@@fluidmechanics101 I will test your suggestion (5 cells across the integral length scale), but I'm afraid that the numbers of cell would increase dramatically. I remember that for a second order method in space, the numerical damping could be "neglected" if the length of a cell is about one order of magnitude smaller than the resolved size. So this would be an even higher restriction. Could you share your resource about the (5 cells across...)? Maybe I misunderstand something.

[@fluidmechanics101]

The recommendation of 5 is from an old ANSYS presentation. I will see if i can find a link for it

[@Key1Kh1]

it was very useful, thank you

[@Snyder0317]

thanks! would love more LES content in the future

[@fluidmechanics101]

Next week! The next video is coming 😄

[@BobBeatski71]

Very insightful, thank you.

[@wanglu5653]

Wow, the video is fantastic! I learned a lot from the video. Could you make some movies about DES?

[@fluidmechanics101]

I will add DES to my list!

[@ardakupelioglu4589]

Thanks for the video.

[@killua9369]

Thank you for this amazing lecture! Which tool in paraview should be used to calculate the lo? Because I usually define a volField in the solver and compile it again

[@fluidmechanics101]

Just use the calculator in paraview. It should be fine. You will need to export the cell volume as a field from your CFD solver though 😊

[@idreeskhan-zp5ey]

Nice talk!

[@ahmed12op]

Awesome, just awesome 👏🏼

[@mdfaiazkhaled1347]

Brilliantly explained.. thank you so much...

[@murtadamohammed8383]

Thanks a lot more than useful.