Fluids

Fluids

dynamic viscosity for grid spacing calculation for airflow with varying temperature

    • Danielgkh
      Subscriber

      Hi everyone,

      I am simulating the airflow in a tube with varying temperature. The inlet temperature is set as 450 C. The outlet temperature is around 200 C after initial simulation. The material is user-defined air.

    • Karthik R
      Administrator
      Hi Wall y+ indicates generally indicates the whether or not you are modeling the laminar sub-layer. Since you are modeling a heat transfer problem, I'm guessing you might want your y+ values closer to 1 (for better accuracy). To achieve this, you might need to further reduce your 1st layer thickness when you generate the computational mesh.
      Again, this also depends on the near-wall treatment you are using (under Viscous models).
      Since you have the two temperatures, estimate the y value based on the two viscosities and pick the lower value and try.
      Karthik
    • Danielgkh
      Subscriber

      thank you very much for your explanation. I am using realizable k-e model with enhanced wall treatment. Does this statement "y+ values closer to 1" applies to this model as well?
      Thanks again in advance.
    • Karthik R
      Administrator
      Hello The results from the Enhanced wall treatment depends on your mesh resolution. If the mesh near the wall is refined enough, it can capture the viscous sub-layer. If it isn't, it behaves similar to a wall function model. It all depends on the mesh. To answer your question, yes - it does have the capability to resolve the sub-layer details (y+ ~1).
      Karthik
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