Flow Converges for AOA 0 1 and 2 but when i increase to 5 or above it diverges

JacobKeddy · May 9, 2024, 15:57

Hi i'm very new to cfd and have spent a few months developing my knowledge and skills for my uni coursework. I need to analyse a NACA airfoil (1412) and am struggling with getting my data to converge.

the config file titled workingT3.cfg in the repository below accurately converges for low AOA (0,1,2) but when i increase to 5 or above my lift and drag coefficients start spiraling out of control.

if anyone could help it would be greatly appreciated.

I have attached a link to my config file (workingT3.cfg) my mesh (farfieldonly.su2) as well as the code used to generate the mesh using gmsh (n1412.geo for geometry and modified.geo for the mesh) I believe my mesh is accurate so shouldnt be a problem there but any advice would be amazing.

I have also attached my Data from xfoil for expected cl and cd values for each angle of attack.

https://github.com/JacobKeddy/SU2-NACA

Thank you,
Jacob

bigfootedrockmidget · May 10, 2024, 09:37

Hi,

How well does your simulation converge?

Have a look at this page:
https://turbmodels.larc.nasa.gov/air...verif500c.html
Here, the farfield is 500 cord lengths away from the airfoil.

Also check the density of the mesh around the airfoil. These mesh settings will influence your results a lot.

JacobKeddy · May 10, 2024, 09:45

Hi,

Thank you so much for your reply i will try separating the farfield from the airfoil because at the minute it is coincident.

Do you know what i should specify the area between the airfoil and the farfield as because when i initially tried this there was an error with an undefined surface between the new far field and the airfoil.

My mesh converges around the airfoil and is much denser around the airfoil than further into the farfield. I will try increasing the density as well.

Thank you so much again

Jacob

May 9, 2024, 15:57	Flow Converges for AOA 0 1 and 2 but when i increase to 5 or above it diverges	#1
JacobKeddy New Member Jacob Keddy Join Date: Mar 2024 Posts: 3 Rep Power: 2	Hi i'm very new to cfd and have spent a few months developing my knowledge and skills for my uni coursework. I need to analyse a NACA airfoil (1412) and am struggling with getting my data to converge. the config file titled workingT3.cfg in the repository below accurately converges for low AOA (0,1,2) but when i increase to 5 or above my lift and drag coefficients start spiraling out of control. if anyone could help it would be greatly appreciated. I have attached a link to my config file (workingT3.cfg) my mesh (farfieldonly.su2) as well as the code used to generate the mesh using gmsh (n1412.geo for geometry and modified.geo for the mesh) I believe my mesh is accurate so shouldnt be a problem there but any advice would be amazing. I have also attached my Data from xfoil for expected cl and cd values for each angle of attack. https://github.com/JacobKeddy/SU2-NACA Thank you, Jacob

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May 10, 2024, 09:37		#2
bigfootedrockmidget Senior Member bigfoot Join Date: Dec 2011 Location: Netherlands Posts: 529 Rep Power: 17	Hi, How well does your simulation converge? Have a look at this page: https://turbmodels.larc.nasa.gov/air...verif500c.html Here, the farfield is 500 cord lengths away from the airfoil. Also check the density of the mesh around the airfoil. These mesh settings will influence your results a lot.

May 10, 2024, 09:45		#3
JacobKeddy New Member Jacob Keddy Join Date: Mar 2024 Posts: 3 Rep Power: 2	Hi, Thank you so much for your reply i will try separating the farfield from the airfoil because at the minute it is coincident. Do you know what i should specify the area between the airfoil and the farfield as because when i initially tried this there was an error with an undefined surface between the new far field and the airfoil. My mesh converges around the airfoil and is much denser around the airfoil than further into the farfield. I will try increasing the density as well. Thank you so much again Jacob