Large Eddy Simulation - comparing Simulation Methods in OpenFoam or Ansys - why one should use LES

This video explains briefly which simulation method is used for what kind of problem. What are the benifits of LES or Large Eddy Simulation compared to RANS.

[TheManolis]

As someone who uses RANS models all the time, LES looks like magic to me

[MartinIsoz]

Hi, thanks for a nice and concise video. I have just few remarks/questions that I would like to be cleared up to avoid potential confusion (at least for me):
1. Using Re=2300 and 2900 as a threshold for laminar/turbulent flow, isn't this value an estimate for a flow in a smooth straight pipe? And even there, it is just an indicator, not a fixed value. I would be much more carefull stating that anything bellow 2300 is laminar and everything above 2900 is turbulent.
2. Listing 'laminar' as a RANS model, I would like to know how got there. AFAIK (and of course, I might be wrong), turbulence is inherently present in the NS equations and manifests itself more and more as the convective term in the momentum balance gains importance. Consequently, solving the flow using 'laminar' turbulence model with high enough mesh resolution to capture the whole energy cascade is DNS. Thus, I would mention the 'laminar' turbulence model either in a separate category or in the DNS box. To list it in RANS, there is just no averaging in 'laminar'.
3. I thought about having a few more rants on the topic of RANS vs URANS and and the necessity of specifying resolved vs modeled energy ratio for any LES simulation but oh boy, for such a nice video, this is a way to long of a comment.

Thanks for making the effort and sharing your work!

[mohamedsereez]

The transition to fully turbulence during external flows is generally characterized at 500, 000 and above for external flows. Also, DNS is a method to resolve all scales of Eddie’s including the kolmogrov scales. The matrix inversion can be applied to any solver formulated with an explicit diagonal matrix. However your simulation visualization is very good

[cliffordbradford]

The laminar to turbulent transition at ~2300 is for flow in pipes, on a flat plate it is ~10^5.

[HolzmannCFD]

It would be very nice to see some more information in the description such as a few more details for the LES. Which filter were used, and numerical schemes for example.

Thanks, Tobi

[TheOnlyRaceEngineer]

Thank you Henrique for such a concise explanation. You did it efficiently just like RANS. Great job. More than happy to subscribe to your channel.

[christianedelmann]

Really impressed with your videos so far definitely an appreciated source of information for someone who is getting into opensource cfd

[realkanavdhawan]

In terms of accuracy Turbulence Models are as under
Sparlts Almarts 1 equation --> kw, SST, ke, kw-SST 2 equation Model --> Reynolds Stress Transport 3 equation Model to find u', v' and w' which will be used to find 9.0 Reynolds Stress Tensor components u'u', u'v', u'w', v'u', v'v', v'w', w'u', w'v', w'w' --> Large Eddy Simulation where Macroscale eddies are resolved and microscale and Kormogolov length scale eddies are modelled based on universal pattern of life cycle --> Direct Numerical Simulation where mesh is refined upto Kormogolov length and Simulation time is lower then Kormogolov time scale in order to resolve entire Eddy life cycle from birth to death by viscosity

[AleX-fgsu]

Nice visualization! Now I know why my hair gets messy in a convertible :D

[AjarnSpencer]

thanks this helps me with my mental experiment thinking about twin jet nozzles emitting converging propulsion force to crash inro each other behind a fighter plane, and wondering if it would be tantamount to sonic the hedgehog

[aerospaceengineer]

nice one, but if you could show how to do it from the beginning that would be appreciated from the engineering community!

[ianm]

Hi everybody, I am Ian, honestly, I think I am too late to learn, now I am a fourth-year student in mechanical engineering but I am new in Ansys
I really want to learn Fluent, but I face a problem that I don't really know when I have to choose the right turbulent mode
I see on youtube they just click K omega SST, K epsilon(realizable & RNG), LES, Spalart-Allmaras, RANS, and so on, but I don't really know what case I have to choose and do my turbulent mode is right or not
do you have a recommendation for me to learn about it in a simple way?
thank you so much

[subhajitbag]

Hey, does ansys work in Windows 10 Home edition ??
And one more thing... Which software should i use.. OpenFoam ir Ansys?
I am very confused.. Please help me out..

[brandonjohnson]

Wait until there is an AI model which can increase efficiency by getting the mesh state equations close to reality, then allowing DNS to converge each time step. I feel AI will learn how the NV equations work, and this will make our lives amazing as sim engineers.

[keyvanhp]

Great. I want to do this simulation on golf ball, Do you send tutorial of this simulation?

[anthonymedrano]

How many cells did you use in your mesh?

[Mehedi]

Can you tell me how to visualize flow like your video (at 3.03s ) in Ansys??

[Michallote]

Hey I have a question, I have a small propeller about 18 inches. The rotational speed is about 6710 RPM. And I swear I've searched a lot on the topic but there is not actually much info on how to properly simulate a propeller. So far I have tested Reynolds Stress Eq. K-omega and K-epsilon. However I really don't know which is better for my needs. I have used a lot of K-omega for fixed wings at low levels of aoa and low reynolds (about a million Re). Which method should I use for rotating propellers?

[ppppp]

It must be URANS and the flow pattern beneath the car is very bizarre.

[TheSzrMedia]

Bu kadar fark ettiğini görünce şoke oldum