
#1
Nov712, 03:51 AM

P: 1

I am trying to perform a CFD simulation of a 70 degree sweep Delta Wing at different angles of attack (aoa = 20, 25, 30, 35 degrees). The inlet flow is at 25m/s. I have made a spherical Farfield boundary with the sphere radius of 5 times the root chord length of the delta wing. Because of the symmetrical shape only half of the delta wing and spherical farfield boundary is considered for meshing. I have made 10 inflation layers on the delta wing surface to capture the boundary layer and an unstructured mesh in the farfield using ICEMCFD. A mesh with 0.7 million cells has been created. Since the Mach no. is low, I have run a steady state Pressure based simulation using SA turbulence model in Fluent. Density of air is taken as constant. The hemispherical boundary is taken as velocity inlet and the symmetry is applied at the symmetrical face. My y+ lies in the range of 0.1  0.6.
I want to know, have i made any mistake in the case setup? what turbulence conditions i need to mention at the inlet velocity boundary condition? I also want to perform simulations with kw SST and kepsilon turbulence models. Is my y+ enough for the simulations with the above mentioned turbulence models? Among all which is a relatively better turbulence model for subsonic CFD simulations of delta wings at high angles of attack? Do i need to make a structured mesh? Your guidance will be appreciated. Best regards 



#2
Nov712, 09:13 AM

P: 101




#3
Nov712, 04:06 PM

P: 208

It'd be nice to see a picture of the mesh. It's kind of hard to imagine. That should be enough cells for the turbulence models, but the mesh has to be constructed well. A picture of it would help a lot.




#4
Nov912, 03:44 PM

P: 263

Delta wing cfd
What makes you think there is a mistake?
There is a lot of information on turbulence modeling in the ANSYS theory manuals, especially for fluent (you didn't mention which solver you use). They also give guidelines for the y+ values, depending on your nearwall treatment. If you use some 'lawofthewall' kind of wall function, y+ actually needs to be large (>30), if you are resolving the boundary layer, y+ needs to be small (<1). You might also want to take a look at some NASA papers on their online NASA Technical Reports database. Some papers give a lot of details on settings, model comparison etc. If your solver knows about structured meshes, it's better because it can be solved faster. Also, structured meshes tend to have higher quality cells. 


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