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Home Forums ANSYS Fluent Beginners to Advanced level Lesson 11 Flow over cylinder Reply To: Lesson 11 Flow over cylinder

  • Rahul

    November 20, 2023 at 12:29 pm

    Hi Karthik,
    Coarser meshes will normally give results with lower residuals but will not be able to capture the flow physics accurately. Please check the range of wall y+ obtained in Fluent after the simulation in the results panel for the 1st cell height you are using.
    I think you are running a 3D model for this case. Then it will be difficult to resolve the domain properly as you are using Ansys Student version and have a mesh size limit. Also, drastically increasing the mesh size will only increase the required computational power.
    I suggest you to try doing a 2D simulation for the same. In that case, you can use a finer mesh and try to obtain the desired wall Y+. The 1st wall thickness for the diameter and velocity you have mentioned seems to be actually lower than the value you mentioned. That is why I suggested to try with a lower Re, so that you can use a mesh with a bigger 1st cell height (For example for Re=5000, you need a first cell height of only 10mm approx. to get wall y+ <5).
    Also, there are lot of reference papers related to flow past a cylinder, both CFD and experimental, which can be obtained by a simple Google search for the Reynolds number and conditions of your choice. Please take a look to get an understanding of the domain sizes, boundary conditions and computational models used.
    Also please use the mesh refinement as I mentioned in the previous post for better results instead of a circular one, since downstream flow physics can only be captured only with a finer mesh in that region.
    Best regards

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