Hi there, I am trying to validate the NACA 4412 hydrofoil in a sea water domain, but my lift and drag coefficients are not even close.
I have followed the Autodesk airfoil modelling webinar and other forum posts and used all these tips.
I would appreciate if someone could quickly review my setup and let me know if they have tips to improve the validate results.
CAD: Sketched the NACA4412 hydrofoil using Autodesk Fusion 360 with airfoil sketch from file plugin. Closed tip with a small tangent arc. Sketched 5 refinement regions scaled outwards from the foil. Patched the sketches into 2D surfaces and simplified using Simulation "simplify" then opened in CFD.
Material:
- Sea water at 293K
- Fixed conditions (not variable)
Boundary conditions:
- Inlet: Velocity V=0.68 m/s (Re = 563,000)
- Angle of attack: 4 degrees (velocity components modified at Vx=V*cos(AoA), Vy=V*sin(AoA) )
- Top/bottom edge slip symmetry
- Outlet pressure 0Pa gage
Initial conditions:
- Same as inlet boundary condition for whole domain
Turbulence:
- SST k-omega RC Hellsten
Meshing:
- Hydrofoil edge element length 0.25cm.
- First region surface element length 0.5cm.
- Following surface regions 1cm, 2.5cm, 5cm, 15cm, 50cm in outer region
- Refinement region following wake to outlet, surface length 2.5cm
- Layer factor: 0.84
- Layer gradation: 1.75
- Wall layers: 15
- After 1000 iterations max y+ is 0.009
- I've used all the flags in the Autodesk webinar e.g. resid_bdry_force_calc = 1
- Total nodes: 80,000
Solver:
- Convergence - tight, + 1 order of magnitude (1e-6/0.0001/0.0001/1e-7) for the four convergence settings
- Incompressible flow
The best results I have achieved is within 10% error of one coefficient, but then 50%+ error in the other. And vice versa.
Are there some specials settings that should be changed when modelling in a water domain versus an air domain?
Could someone please let me know what I'm doing wrong here, or how to improve the results?
Thanks, Alastair
Mesh:
