At 09:57 PM 21/10/03 +0930, you wrote:
>I responded to the first post on this topic with the comment of 'low drag
>turbulator'. I'll amend that comment slightly with 'low drag way of
>avoiding separation bubbles'.
snipped
>
>Having scanned a couple of technical papers this evening, I'll see if I can
>translate it into everyday English. I'll apologise for any technical
>inaccuracy that I will introduce for the sake of everyone's general
>understanding. (Hopefully I'll have got this right.)
>If the wing makes up 40% of your total drag at this speed, then your total
>drag reduction is only 2.68%. Enough to take your 38:1 glider up to 39:1
>
>So is it snake oil? In theory no it is not. It is possible that Sinha's
>strip will be better than the turbulators we have now.
>
Thanks Anthony,
Three comments
- the bubble is usually smaller on the top surface because to get one you
need a favourable pressure gradient for laminar flow and low Reynolds
numbers. This occurs on the lower surface at low speeds/high angle of
attack. On the top surface the low angle of attack case occurs at higher
speeds where the Reynolds numbers are higher and hence the bubble doesn't
form or is small.
- Jim Hendrix ought to fly the Cirrus with a conventional turbulator and
see what happens with all the other equipment being the same. Either the
Cirrus has terrible laminar bubble on the lower surface or the deturbulator
does somethiong other than cause an orderly turbulent transition.
- Glider designers would probably sell their grandmothers for a nearly 3%
performance increase.
Mike
Borgelt Instruments - manufacturers of quality soaring instruments
phone Int'l + 61 746 355784
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