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  1. ghylander

    Rotational stiffness from eigen frequency

    Circling back to the OP, is this something that one just has to live with? If I want to solve for the rotational stiffness, it'd best if I forget radians are involved in the equation, then the result will be N.m/rad?
  2. ghylander

    Rotational stiffness from eigen frequency

    So it's fine then to just solve with no regard to the radians, then simply plug it in? I.e.:
  3. ghylander

    Rotational stiffness from eigen frequency

    Hi all, thanks for your replies. My question is not so much about "why radians", but "why LHS is radians/s and RHS is 1/rad · s)" I have formatted the equations, I hope this makes it clearer: The question is: Why in equation 1, LHS is in [rad/s^2] while RHS is in [1/rad·s^2], and in...
  4. ghylander

    Rotational stiffness from eigen frequency

    Hi all, I have this doubt when it comes to estimating a rigid body rotational stiffness from a eigen frequencies analysis. At first it seemed straightforward to me, using the fundamental dynamics equation w_n = sqrt(K/M), where w_n = f_n · 2 · PI However, I seem to be reaching a unit...
  5. ghylander

    Use of MFLUID for external fluid field

    Hi all, I am doing some SOL103 analysis on certain subsystems of a floating structure, and I'm exploring different approaches at representing the whole structure's added mass. One of my approaches is to simply represent the floating structure as a rigid body, using a CONM2 element. This way...
  6. ghylander

    Data surface pressures on either side of surface

    Of course they can be summed 'easily'. I mean that, because one side of the surface is loaded in all its area, while the other side is only being partially loaded, care must be taken with the data surface interpolation. If the CFD and FEM meshes are very different, it could lead to...
  7. ghylander

    Data surface pressures on either side of surface

    After runnin similar tests for the followig geometry: The results are similar to the previous tests. The drawback is that the pressures cannot be easily summed together. Because of the interpolation, different mesh geometry between CFD and FEM, and different CFD mesh for each surface, you'd...
  8. ghylander

    Data surface pressures on either side of surface

    After checking the applied force vs reactions, I actually realised I made a mistake when inputting the data surface with the summed pressures, I entered 9.5e-4 instead of 9.5e-5. I corrected the issue and re-run the tests, and now all 4 methods check out correctly. While this was a great find...
  9. ghylander

    Data surface pressures on either side of surface

    I did the tests you proposed, and I got some wild results. I performed a total of 4 different tests: 1- Apply load on elements, each pressure on a different data surface, selecting face 1 or 2 2- Apply load on elements, using a data surface summing the pressures on each face 3- Apply a load on...
  10. ghylander

    Data surface pressures on either side of surface

    Hi karachun Thanks for the post. I think the case of a billboard under wind load sounds like a fitting aproximation. This is a quick sketch: You can visualize it as a CD, where the 3rd surface woul be the edge itself. I will try the simplified test, hadn't thought of that. Fingers crossed...
  11. ghylander

    Data surface pressures on either side of surface

    I have some pressure data coming from a CFD analysis. After reading through the multiple posts here and watching videos on youtube, I was able to mostly apply the pressures to my model in a coherent way. I'm having trouble regarding a specific area of the structure, however. In the CFD...

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