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stabilize laminar boundary using distributed suction through a perforated surface or thin transverse slots
A laminar b.l. has a lower skin friction coefficient (and thus lower drag)
A thin b.l. delays separation and allows a higher C L max to be achieved
Ref: McCormick, “ Aerodynamics, Aeronautics and Flight Mechanics ,” pg. 202. plenum chamber outer skin inner skin Boundary layer thins and becomes fuller across slot
Notable Laminar Flow Control Flight Test Programs Ref: Applied Aerodynamic Drag Reduction Short Course Notes, Williamsburg,VA 1990. effects of sweep on LF encountered full chord LF R C = 47x10 6 new LF wings for program suction through nearly full span slots – both wings X-21 (Northrup/USAF) jet bomber 30 ° sweep 1963-1965 no special maintenance required lost LF in clouds & during icing LE protection effective LF maintained to front spar through two years of simulated airline service two leading edge gloves Lockheed – slot suction & liquid leading edge protection McDD – perforated skin & and bug deflector JetStar (NASA) 4-engine business jet 1985-1986 at M local >1.09 shocks caused loss of LF Full chord LF 0.6 < M < 0.7 R C = 36x10 6 NACA 63-213 upper surface wing glove suction – 12, 69, 81 slots F-94 (Northrup/USAF) jet fighter 1954- 1957 Monel/Nylon cloth 0.007” perforations full chord LF M~0.7 / R C =30x10 6 upper surface wing glove suction - porous surface full chord suction Vampire (RAE) single engine jet 1955 Engine/prop noise effected LF surface quality issues LF to 45% chord (LF to min C p ) R C = 30x10 6 NACA 35-215 10’x17’ wing glove section suction slots first 45% chord Douglas B-18 (NACA) 2-engine prop bomber 1940 Comments LF Result Test Configuration Aircraft Date