questions about inflation layers /turbulence

    • manelaero2020

      Hi friends ; 

      In the case of a laminar flow : 

      1/ Do users must define inflation layers also? I don't think because the objective of the inflation layer is to resolve Y+ near the wall, in the order to capture the logarithmic velocity profile in the case of turbulent flows. 

      If not, what user must do? ( in the case of a CFD solver such fluent) 

      2/ If I have a turbulent flow everywhere, and a few computation resources; can I put inflation layers only in the zones of interest? I mean, does this choice can affect the accuracy of results? 

      3/ What is the approximative value of Reynolds which corresponds to transition to turbulence for external flows? 

      Thank you for your help


    • Danica
      Ansys Employee


      So for any flow, laminar or turbulent, the inflation layers do need to be defined as this is the area of the boundary layer. If you do have have few computation rescources you can refine your inflation layers to the areas of interest, but yes this will effect the accuracy of your results in the lesser refined areas. Have a look at the following for further explanation on near wall treatments and their significance to the solution:

      4.18.1. Overview (ansys.com)

      With respect to the Reynolds number, a quick google search should give you the relevant numbers for transition to turbulent flows in different conditions.

      Would also recommend having a look at some of these courses for help with mesh refinement: Fluids Engineering Courses | Ansys Innovation Courses

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