Fluids

Fluids

Moving overset mesh

    • nvspronsen
      Subscriber
      Hello everyone,nnI want to perform a simulation with an overset mesh, where the background mesh contains a certain flow profile, and the component mesh (in 2D a circle, and in 3D a sphere), follows that flow profile. nRight now I am a bit confused on how to handle this problem. First I was thinking about using 6DOF, however, than I will create forces which will act on the component mesh whereas I want the component to follow the background mesh.nIs there anyone who has an idea on how to tackle this problem or has some tips?n
    • Stephen Orlando
      Ansys Employee
      Hi, nCan you provide some further details on the flow profile that you mentioned including images of the mesh and the Fluent setup? Is this flow profile imposed on a boundary only? It sounds like 6dof is what is needed, but more info is needed to say for sure.nThanks,nSteven
    • nvspronsen
      Subscriber
      Yes of course. First I will show you the mesh I created before and after hybrid initialization. For the intialization, I turned off the overlap minimizaton, to increase the overlap, because I thought this would increase the accuracy and prevent errors during simulation.nnFor my Fluent set-up I used: Transient, pressure-base, absolute, planar. With the following model and boundary conditions. About the boundary conditions of the component wall, I doubted whether to use 'no slip' or 'specified shear' and than setting the shear stress to 0, so I tried both, but it did not give any difference in outcome.nAfterwards I compiled the following SDOF, where I only entered the mass and inertia IZZ. And enabled Dynamic mesh: Six DOF and implicit Update. nBelow are the methods that I used and the calculations settings. nSo actually when I enabled the 'write history motion', my overset grid went down (I believe) because CG_Y started at 2.5 and ended at 2.4789, and this happened in 0.161 seconds. However, after that moment the error occured that a negative cells volume was detected. I have attached a photo where the negative cell volums are encircled. So basically my question still remains, whether is the right approach? So assiging the mass and inertia through a udf - SDOF and than applying a pressure or flow filed in Fluent. And if this is the case, than how will I remove the error of negative cell volume? Should I reduce the time step size or maybe make the cells, that cause problems, smaller?nThank you in advance!n
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