[JackFischer]

Hey Folks,

I want to investigate drag and lift of a few three element airfoils. In order to check the validity of my results I did a simulation of a design I have some former results from. Now the clue: My results vary from those I already have from another simulation. As you can see in the pic, my simulation (lower one) produces stall after the second blade, while the upper one doesn't.

Its the exact same model in a more or less same dimensioned windtunnel, with moving floor. My mesh is as accurate as the mesh from the original, I use same turbulence model (K-epsilon) and same other physiks and meshmodels. After 1000 iterations in steady I switch to unsteady and do another 6000 iterations. My values for drag and lift coefficient converged pretty well over the last 2000 iterations.

What are your first thoughts, when you see the different flow behaviours? Any tip is welcome

Best wishes,
Jack


Edit: Just rememberd stuff from classes and thought about the courant number. I'll check the cell size and timestep in unsteady mode, maybe that's my issue.

[me3840]

Those meshes are far too coarse in the downstream area, you can see the diffusion really easily.