Thanks for the great content, Cillian! I really appreciate the thorough explanation. I’m currently conducting CFD analysis on a symmetric airfoil to derive its lift curve. However, when I approach the stall angles, the solution struggles to converge, and the lift coefficient starts oscillating between two values, forming a sinusoidal pattern. How did you handle this for post-stall values? Did you average the oscillating results, or use a different approach?
Awesome analysis! I have 2 questions; - for the k-epsilon model, the y+ requirements differ from that of the k-omega model; would it be preferrable to also create a mesh with that in mind? Sure, it doesn't make the simulations comparable directly, but running rerunning the cases on this second mesh could work as well - when looking at experiment results, do you happen to know what the measurement process or workflow was? Essentially, you are comparing a computational 2D domain to a set of results that were carried out in 3D and then later derived to give 2D results? I am quite clueless on this.
Hi, Yes, if using k epsilon there are different y+ requirements, and the solver will use wall functions to model the effect of the boundary layer rather than resolving it, hence a coarser mesh can be used in these cases, provided the user is aware that boundary layer effects may be less accurate. Yes, the data was taken from a 3D case and converted to a “section lift coefficient” which represents lift per unit span.
@@cillianthomasengineering what do you guys mean by the k-epsilon requires a diffrent y+ value; should the y+ value be lower or higher or what exactly? thank you for the wonderful video btw
![[CFD] The k-omega Turbulence Model](http://i.ytimg.com/vi/26QaCK6wDp8/mqdefault.jpg)
![[CFD] The k-omega Turbulence Model](/img/tr.png)
thank you so much!
Thanks for the great content, Cillian! I really appreciate the thorough explanation. I’m currently conducting CFD analysis on a symmetric airfoil to derive its lift curve. However, when I approach the stall angles, the solution struggles to converge, and the lift coefficient starts oscillating between two values, forming a sinusoidal pattern. How did you handle this for post-stall values? Did you average the oscillating results, or use a different approach?
I used the Shear Stress Transport k-omega model
can you do a video on NACA 64-618
Awesome analysis! I have 2 questions;
- for the k-epsilon model, the y+ requirements differ from that of the k-omega model; would it be preferrable to also create a mesh with that in mind? Sure, it doesn't make the simulations comparable directly, but running rerunning the cases on this second mesh could work as well
- when looking at experiment results, do you happen to know what the measurement process or workflow was? Essentially, you are comparing a computational 2D domain to a set of results that were carried out in 3D and then later derived to give 2D results? I am quite clueless on this.
Hi,
Yes, if using k epsilon there are different y+ requirements, and the solver will use wall functions to model the effect of the boundary layer rather than resolving it, hence a coarser mesh can be used in these cases, provided the user is aware that boundary layer effects may be less accurate.
Yes, the data was taken from a 3D case and converted to a “section lift coefficient” which represents lift per unit span.
@@cillianthomasengineering what do you guys mean by the k-epsilon requires a diffrent y+ value; should the y+ value be lower or higher or what exactly? thank you for the wonderful video btw