Very strange results with turbulent simpleFoam simulations on airfoil

tnee3 · February 14, 2024, 16:29

Hi!

I’d firstly like to apologise for how open ended this post is going to be. I’m trying to run 2d turbulent simulations of an airfoil using simpleFoam, and meshing with snappyHexMesh.

When I run the case without the viscous layers added, obviously my values are wrong as the boundary layer is not resolved but it runs okay. However when I add the viscous layers, the simulations produce very strange velocity plots in paraview. I will attach some of these plots below.

vector_plot_1.png vector_plot_2.png

I know this is very broad and I’m sorry but I’m completely stumped by it. Any help on this would be really great, thanks!
I’ve also attached my snappyHexMeshDict, controlDict, and initial conditions for velocity pressure and turbulence model parameters (k-omega SST model). Please let me know if there’s any other files I should upload.
Files.zip

samisafarini · February 15, 2024, 05:38

Is the simulation for a wind tunnel? it seems odd that your top and bottom are nonslip. I find setting a pressure of 0 gives me problems have you tried setting it as absolute atmospheric i.e. 100kpa?
Can you share the whole sim folder with us?

tnee3 · February 16, 2024, 10:47

Hi there, thank you for responding to me, sorry I took a while to respond.

My issue actually ended up coming down to my mesh, it simply was not good enough. I was also using renumberMesh to optimise it as I read somewhere to do that and for whatever reason that was giving me the second very strange plot. I have somewhat fixed the issue now, but still need to refine the mesh further to solve the boundary layer. Thanks again for the response though!

February 14, 2024, 16:29	Very strange results with turbulent simpleFoam simulations on airfoil	#1
tnee3 New Member Tommy Nee Join Date: Sep 2023 Posts: 11 Rep Power: 2	Hi! I’d firstly like to apologise for how open ended this post is going to be. I’m trying to run 2d turbulent simulations of an airfoil using simpleFoam, and meshing with snappyHexMesh. When I run the case without the viscous layers added, obviously my values are wrong as the boundary layer is not resolved but it runs okay. However when I add the viscous layers, the simulations produce very strange velocity plots in paraview. I will attach some of these plots below. vector_plot_1.png vector_plot_2.png I know this is very broad and I’m sorry but I’m completely stumped by it. Any help on this would be really great, thanks! I’ve also attached my snappyHexMeshDict, controlDict, and initial conditions for velocity pressure and turbulence model parameters (k-omega SST model). Please let me know if there’s any other files I should upload. Files.zip

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February 15, 2024, 05:38		#2
samisafarini New Member Sami Safarini Join Date: Sep 2021 Posts: 8 Rep Power: 4	Is the simulation for a wind tunnel? it seems odd that your top and bottom are nonslip. I find setting a pressure of 0 gives me problems have you tried setting it as absolute atmospheric i.e. 100kpa? Can you share the whole sim folder with us?

February 16, 2024, 10:47		#3
tnee3 New Member Tommy Nee Join Date: Sep 2023 Posts: 11 Rep Power: 2	Hi there, thank you for responding to me, sorry I took a while to respond. My issue actually ended up coming down to my mesh, it simply was not good enough. I was also using renumberMesh to optimise it as I read somewhere to do that and for whatever reason that was giving me the second very strange plot. I have somewhat fixed the issue now, but still need to refine the mesh further to solve the boundary layer. Thanks again for the response though!