single element rear wing vs multi element rear wing

[Greg Locock]

jeez louise, go away ,find some data, then have a proper discussion. Fig 6-77 in katz plots L/D and CL for 1 2 3 and 4 element wings. L/D drops, CL rises.

[andylaurence]

Fig 6-77 in my copy of Katz is the underside of the front of a sports prototype. The closest I can find in my copy is 6-71, which is multiple elements on top of each other, rather than a slotted wing (main plane & flap) as I'd describe a multi-element wing, but -L/D drops and -CL rises as you say. I'm keen to understand the interaction of a main plane and flap when the slot gap varies and the location of the two elements is varied.

[Greg Locock]

Milliken fig 15-25 shows some results for some very complex wings (4 airfoils in series). I'd have thought a DOE was the best approach if your wings are of fixed size and section you've got 6 factors (x z alpha for each airfoil). CFD might be informative, but it will probably be misleading (I've seen some absurd accuracy claims on this board).

[Greg Locock]

here's a fairly detailed study for moving a flap around relative to a Clark Y section, in free air. I'd expect that the results for a wing near the diffuser of a GE body would be quite different, really other people's experiments will just show trends not answers.

http://hdl.handle.net/2060/19930091502