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Frequently Asked Questions
Q. Didja know the inboard lower surface is wavy?
A. Yes. It's in the Wing definition, and since it's on the lower surface, it should have little effect on drag. It'll be in everyone'z solution, okay?
Q. How can we match the wind tunnel data with fully turbulent calculations?
A. We can't. We decided that, since it would simplify the calculations (and some codes may not be able to specify a transition location), it would be easier and encourage more participation. The fully turbulent analysis will cause a shift in the drag and possibly a change in the onset of buffet. Since the drag data provided with the AGARD files is only given to 10 counts of resolution, that will limit our comparison with the wind tunnel data anyway. We will emphasize the statistical comparison between the numerical solutions first, then with the wind tunnel data.
Q. The IGES file of the DLR-F4 geometry is not closed and has gaps between several panels/faces. Shouldn't the geometry be repaired so we all use exactly the same geometry?
A. The committee discussed the fitness of the geometry, and it was observed
that the model was not completely "watertight". We believed that the holes
were minor, and that they would not affect the solution significantly. This
geometry is fairly representative of a starting point for CFD models, and
was used to generate the standard grids without difficulty.
We understood that some participants may need to close the geometry in order
to generate their own grids. If this is needed, do so as you see fit, but
please document what you did in your report.
