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# les-ras
  • l
    And this explaination would explain why URANS fails to capture vortex shedding, but WRONG. There are some paper where they do capture it at the proper frequency anyway, by using transitional models (still URANS). So I'm not satisfied with this expalination 😄
  • l
    Now, I did my case: real trailing edge (as seen in the picture above) : URANS doesn't predict shit, never - LES does work nice blunt trailing edge (like straight cut) : URANS Transition does predict good frequency (like in the paper) - LES also
  • l
    BUT, for the blunt trailing edge, URANS transitional model has an amplitude 10x smaller than LES calculations. Soooo, ye the vortex is here, but way less strong than for LES, so I guess it is still wrong. whyyyyyyy? Since the time scale doesn't seem to be the problem.
  • l
    If you read till here, here is a slice of 🍕 for you
  • l
    🍕
  • t
    nice 🙂 which URANS Modell have you used? I think the model choice has also a big influence, for example have you tryed Spalart Almaras?
  • l
    kwSSTLM
  • l
    I stop with URANS and 2D, I'll focus on WALE 3D, I need to finish this sheit one day ^^
  • t
    yeah 😄 just wanted to say that in RANS the solution really depeend on the used model 😉 but anyway LES is always better and more fun 😄
  • b
    My first LES, is it ok?
    pagani-les
  • t
    check out literature data compare and see if you are near the reality, without any information about the simulation nobody can say anything about the model. In my opinion with this kind of information you also could have done it with blender, but then you should use better colours.
  • b
    @User How to set the value of Delta T?
  • b
    @User pisoFoam the LES motorbike tutorial ,Motorbike first runs in steady state and then in Les mode.
  • b
    How can I do that?
  • c
    What would be starting point for performing LES simulations of flow over an oscillating airfoil?
  • c
    Any leads will be appreciated 🙂
  • t
    I would start with a standard 3D Airfoil Case to get the LES running
  • c
    Great! I am very new to LES! Can you guide me?
  • t
    ofc I can give you some tips if you have some questions 🙂 I think @User is also an expert in that topic 😄
  • c
    Wonderful! Then I already have two mentors 🙂
  • c
    @User @User
  • c
    Is there a tutorial case for LES of 3D airfoil?
  • t
    I dont know excactly but I would just take a 2D Airfoil and make a 3D case out of it
  • l
    What do you want to capture @User ?
  • c
    Scale resolved vorticity field
  • l
    I have a tiny experience with that, as I tried last summer. The goal was to properly capture the vortex shedding frequency of a hydrofoil
  • c
    during the unsteady motion
  • l
    to capture that, RANS was pretty much useless, so I went for LES
  • c
    Yes, something like that
  • c
    RANS is not giving good results
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