Search found 126 matches

by techGuy
Thu Apr 13, 2023 2:11 pm
Forum: CfdOF / CFD
Topic: cfmeshing hell - 30P-30N Validation Case
Replies: 48
Views: 7362

Re: cfmeshing hell - 30P-30N Validation Case

Lift/drag should always be perpendicular/parallel to the free stream. Otherwise you are talking about the normal and axial coefficients, which are something else. OK. My guess is they are changing the free-stream direction to achieve the change in angle of attack, rather than changing the geometry....
by techGuy
Thu Apr 13, 2023 2:09 pm
Forum: CfdOF / CFD
Topic: cfmeshing hell - 30P-30N Validation Case
Replies: 48
Views: 7362

Re: cfmeshing hell - 30P-30N Validation Case

Did you have a look at the settings in the Wolf Dynamics solver files ? Yes - the settings I highlighted are what I feel are the most likely culprits when comparing the two. However it would be important to be systematic here. First see if you can reproduce the correct result using the WD settings ...
by techGuy
Wed Apr 12, 2023 7:21 pm
Forum: CfdOF / CFD
Topic: cfmeshing hell - 30P-30N Validation Case
Replies: 48
Views: 7362

Re: cfmeshing hell - 30P-30N Validation Case

Would be interesting to get the original raw data from the windtunnel test and the parameters of the experimental setup. Why? Klausmeyer writes that the chord of the stowed configuration is 22 inch long. That means we must downscale our model by a factor of 0,56. To reach Re=5*10^6 at normal atmosp...
by techGuy
Wed Apr 12, 2023 7:03 pm
Forum: CfdOF / CFD
Topic: cfmeshing hell - 30P-30N Validation Case
Replies: 48
Views: 7362

Re: cfmeshing hell - 30P-30N Validation Case

I am not an aircraft designer, but the definition of the lift-vector (allways perpendicular to the chord line) sounds strange . Mmmh... not strange when the aircraft itself is the reference. Turning the wing turns the whole aircraft, I know, it is confusing. It's like the chord measurement of the 3...
by techGuy
Wed Apr 12, 2023 3:03 am
Forum: CfdOF / CFD
Topic: cfmeshing hell - 30P-30N Validation Case
Replies: 48
Views: 7362

Re: cfmeshing hell - 30P-30N Validation Case

I get the same numbers and they are wrong. See the link that I provided for the results other people are getting with OpenFOAM. There are a couple issues but the main problem is that the CfdOF templates are not using SA to the fullest extent and there is too much smoothing in the solvers. I am in t...
by techGuy
Tue Apr 11, 2023 11:20 pm
Forum: CfdOF / CFD
Topic: cfmeshing hell - 30P-30N Validation Case
Replies: 48
Views: 7362

Re: cfmeshing hell - 30P-30N Validation Case

Cl for the 30P-30N at 14 degrees and Re=500,000 should be about 3.7. Source: https://ntrs.nasa.gov/api/citations/19970027380/downloads/19970027380.pdf 30P-30N Cl vs AoA.png I'm working with a number of high lift airfoils. CfdOF is near the correct value at 0 AoA, but way low at higher angles of atta...
by techGuy
Mon Apr 10, 2023 4:47 pm
Forum: CfdOF / CFD
Topic: Editing CfdOF templates to use different solvers ? SA and others.
Replies: 5
Views: 1060

Re: Editing CfdOF templates to use different solvers ? SA and others.

See the discussion here (viewtopic.php?p=674704#p674704), starting on page 4 about problems with the current CfdOF solver templates.
by techGuy
Mon Apr 10, 2023 4:18 pm
Forum: CfdOF / CFD
Topic: cfmeshing hell - 30P-30N Validation Case
Replies: 48
Views: 7362

Re: cfmeshing hell - 30P-30N Validation Case

Could you attempt a few simulations at higher AoA ? Here are some results at 8/12/16 deg AoA. Forces are computed on 150 mm mesh-thickness, inlet 90 m/s, rho=1,25, nu=1,5E-5, 5% turbulence k-omega. In all cases I get good convergence down to 10E-4. The skew error in the mesh drops to 4 for 12/16 de...
by techGuy
Sun Apr 09, 2023 12:03 am
Forum: CfdOF / CFD
Topic: Is this a meshing error ? (Patches not found)
Replies: 2
Views: 814

Re: Is this a meshing error ? (Patches not found)

oliveroxtoby wrote: Fri Apr 07, 2023 6:47 pm
techGuy wrote: Fri Apr 07, 2023 7:46 am When I write my mesh case I see this:
These warnings are expected and don't necessarily indicate anything wrong.
Thank you for clarifying that.
by techGuy
Sat Apr 08, 2023 11:56 pm
Forum: CfdOF / CFD
Topic: cfmeshing hell - 30P-30N Validation Case
Replies: 48
Views: 7362

Re: cfmeshing hell - 30P-30N Validation Case

... If you are using the model I supplied the physical chord is what you measured but the folded chord is 1.0m. The industry, including WD, measures co efficients against the folded chord, ie 1.0m. So your numbers corrected to the folded chord would be 2.11 and 0.0656. You are pretty close on the l...