dynamic viscosity for grid spacing calculation for airflow with varying temperature

- May 25, 2021 at 10:08 am
  
  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.
- May 25, 2021 at 1:03 pm
  
  Karthik Remella
  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
- May 25, 2021 at 1:23 pm
  
  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.
- June 7, 2021 at 11:49 am
  
  Karthik Remella
  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