Fluids

Fluids

Horizontal Axis Turbine Blade analysis issues

    • Pranjal193
      Subscriber

      I wanted to mesh a NREL Phase VI Turbine Blade (with a slot) in ANSYS meshing and according to the reference article and my understanding it is vital to have inflation layers. However when I try that, low quality, highly skewed elements are created which obviously lead to inaccurate results and in my case, divergence. So I tried with a simple tet mesh, and am adapting the mesh every 3-4k iterations according to y+.

      The quantity I am interested in is the torque generated, therefore I am looking at the moment about rotation axis and it is nowhere near the expected value (I am getting much lesser values) . Moreover, the torque values are decreasing as I keep adapting the mesh (I expected it to get closer to the expected value). Also, the decrease is quite significant (110 Nm to 90 Nm after adapting it the 4th time). The drag value (in direction of the rotational axis) also changes but not as much.

      Why is this happening? Is it due to the simple tet mesh? In that case how do I create an inflation layer without increasing skewness? My analysis is to gauge the effectiveness of a slot for boundary layer control to increase torque on the blade. I am using the SST k-omega model with a rotating frame(moving reference frame). Additionally, I do not have ICEM CFD (which most sources on the internet have used to mesh the same geometry).

    • Keyur Kanade
      Ansys Employee
      The min orthogonal quality should be above 0.1 to proceed to solver. If it is less than 0.1 then please improve the mesh.
      First check the locations of the bad elements. Please see following video for the same.

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      Once you have locations, please check if you can improve mesh using different mesh sizing. Please see following video.

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      If this does not help, please go to geometry and modify or simplify geometry at those locations in SpaceClaim.
      Regards Keyur
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  • Murari Iyengar
    Ansys Employee
    Hi Pranjal193 Since the geometry is complex, a hex mesh or a hybrid mesh with hex for the blade and tet for the domain will be more suitable. To lower skewness, you can employ different meshing techniques such as sizing, biasing etc. In order to reduce the cell count, you can also model only a portion of the geometry if it is axisymmetric. Inflation layers are necessary for this simulation so if your cell sizes are too large/skewed you can get inaccurate results. You can take a look at the below tutorial for tips about mesh refinement.
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