Fluids

Fluids

Topics relate to Fluent, CFX, Turbogrid and more

3d Inner and outer sphere – vibration – fluent

    • shehab Gamrah
      Subscriber

      The below picture is a cross section view of my model. its an outer sphere enclosing an inner sphere, separated by fluid, so 2 walls and a fluid. My question is how can I vibrate the inner sphere at 3 m/s in the directions stated by arrows, while the inner sphere won't touch the outer sphere after vibrating. so the inner sphere should move upwards, downwards, left and right as if vibrating.

    • YasserSelima
      Subscriber
      In fluent, You need to use DEFINE_CG_MOTION ... give your inner wall the required velocity each time step.nMathematically, You need to make sure that S=sqrt(x^2 + y^2) < R_large - R_smallnn
    • shehab Gamrah
      Subscriber
      I have 3 questions,nDo I need to specify UDFnWhich option should I use MRF, Sliding Mesh, Dynamic MeshnWhich option would create animation of sphere movingn
    • YasserSelima
      Subscriber
      1 - You must use UDF for this simulation. My above DEFINE_CG_MOTION is a UDF macro ... n2 - You have to use Dynamic mesh, After compiling the UDF, it should appear in the Dynamic mesh panel for hookup n3 - To create animations ... create the frame you want and then go to Solution>Animation ... select your frame and the other options. Save HSF files, it takes more space but you can have more options when creating the animation n
    • YasserSelima
      Subscriber
      one more thing, animations will make the simulation run very slow ... so, save the frames every certain flow time .. let's say 0.001 seconds, so you don't create frame every time stepn
    • shehab Gamrah
      Subscriber
      Hey this is my first time to use a udf, can you give me any tutorial on how to specify udf coden
    • YasserSelima
      Subscriber
      Search the forum, you will find many threads and some have the function. Also in the UDF manual there is an example that integrates the pressure on a wall to determine the velocity. Here is one post that has an oscillating wallnnhttps://forum.ansys.com/discussion/comment/102754#Comment_102754
    • shehab Gamrah
      Subscriber
      Hey all, I've never used udf before can someone help to write the udf.nthe inner sphere is translating upawards, downards, left, right at 1m/snand it is not touching outer spheren
    • Rob
      Ansys Employee
      There is guidance in the manual, otherwise search for the macros on here (there's a list in the UDF manual for moving and deforming mesh). n
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