General Mechanical

General Mechanical

FLAG simulation – intend to make the fabric drop under gravity

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    • vbb96vbb
      Subscriber
    • Karthik R
      Administrator
      Hello,nInstead of attaching videos, could you post some screenshots or embed a gif into your post? Ansys employees are not able to download attachments from the forum.nAlso, are you running a transient structural analysis in this problem? I just want to confirm if there is not Fluid flow involved at this time. Please let me know.nKarthikn
    • vbb96vbb
      Subscriber
      Thank you so muchnHere are the screenshots,nAnd affrimative - I am running this simulation as a transient structural analysis now...There is not Fluid flow involved at this time.nn
    • Karthik R
      Administrator
      Hello,nLet me check on this with a Mechanical expert and get back to you.nKarthikn
    • Ashish Khemka
      Ansys Employee
      nnHow is the fluid connected to the pole? I do not see any contact between flag and pole.nnRegards,nAshish Khemkan
    • vbb96vbb
      Subscriber
      Thank you - there is no established contact but that side of the flag (fabric) is fixed... so the pole is a representation: but idle.nI am only focused on the flag (materials); Intending to make it drop under gravity.nn
    • vbb96vbb
      Subscriber
      Thank you so much nI am looking forward to hearing from you soon.n
    • Karthik R
      Administrator
      Hi,nSince I'm don't have a deep knowledge of structural mechanics, is going to be helping you with this one.nKarthikn
    • Ashish Khemka
      Ansys Employee
      nnI think you have defined the Elastomer Sample model for the cloth. Do you think that the fabric of Young's modulus of ~ 1342 MPa? Also, how is the flag deforming when applying standard earth gravity? Can you please share a snapshot of the same?.Regards,nAshish Khemkan
    • vbb96vbb
      Subscriber
      Thank you
    • vbb96vbb
      Subscriber
      Thank you nYes, I did define the material model appropriately and I will share some reference extract.nnBurnett, B . Coupled fluid-structure interaction modeling of a parafoil. PhD Dissertations and Master’s Theses, 2016, p. 74nnYes, I think that the fabric of Young's modulus of ~ 1342 MPa, and please kindly find attached the imagery from a work.n nAccardo, Giampiero & Eugeni, Marco & Mastroddi, Franco & Romano, Giovanni. (2013). Experimental and numerical modelling for flag flutter. pg. 9nnAnd - this is the deformation of the fabric under gravity.nn
    • vbb96vbb
      Subscriber
      please I wanted to follow up to know if there is any update thanksn
    • Ashish Khemka
      Ansys Employee
      nnI think you want the flag to be dropped to a position something like this -nnn(Image snip from google search)nnIf this is the case then I do not think that elastomer is the material to model it.nnRegards,nAshish Khemka
    • vbb96vbb
      Subscriber
      Thank you for the response, your time, and the information.nnYes, correct - I need the flag to be at rest at the Imaged position, under gravity.nIf I can't use elastomer as the material, please what can I change it to in order to get successful at this?.Thank you so much. n
    • Ashish Khemka
      Ansys Employee
      nnI think composites can be used to model fabric but I have limited knowledge on the same. I will check if someone can comment on the use of composites.nnRegards,nAshish Khemka n
    • vbb96vbb
      Subscriber
      Thank you n
    • Mike Rife
      Ansys Employee
      Hi @vbb96vbb nYou have run into a classic issue with Finite Element models being too perfect. The flag is modeled as a perfectly flat surface with gravity acting in the plane of the surface. Our instincts are to expect the FEA result to show the flag droop, since that is our real-world experience. But in the real world the flag is not perfectly flat. There are really ripples in the fabric. nTo overcome this try a static-linear buckling-transient linked system approach like so:n
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      nAnyway you will need to drag-and-drop the Engineering data and the Solution of the Buckling to the Transient Model cell manually. Set up the Static case as you already have: with the flag fixed on the left side, and apply gravity (-Y). When the solve is done change the buckling to find say 10 modes. Then pick one that kind of looks like a fluttering flag. If none suite your needs try solving for more modes. Note the scale factor on the results used so we can see the displacements. From the Mechanical Help -> Application Interface -> Ribbon -> Context Tabs; Result Context Tab we can see this image (scale factor here):n
    • Mike Rife
      Ansys Employee
      Drag and drop the whole Eigenvalue buckling onto the Solution cell of the Static structural system. Miken
    • vbb96vbb
      Subscriber
      Great, it worked...I would finish upnThank you so much n
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