A SIGNIFICANT INCREASE IN LIFT-TO-DRAG RATIO OF AIRFOILS AT LOW REYNOLDS NUMBER THROUGH THE USE OF MULTIPLE TRIPPERS AND LOW DRAG LAMINAR FLOW: TRIBUTE TO THE WORK OF DR. WERNER PFENNINGER

Authors

  • BRUCE CARMICHAEL

Keywords:

Aerodynamics, Structures, Design

Abstract

Low turbulence experimental data obtained in 1956 but not widely published heretofore, provides promise of considerable A-2 performance improvement. ln restricting bolh thickness and camber below traditional values and placing a trip step just sufficiently forward to match the design Reynolds number, Dr. Werner Plenninger was able to keep the prolile drag only 55% in excess of the drag of two sides of a laminar plate. ln spite of a design lift coefficient of only 0.77, both section L/D and section L3/2/D are quite superior to any other data found to date. Application of this data to an A-2 performance study reveals that the minimum allowable wing loading of 0.247 #/sq.ft. and optimum aspect ratio of 20 resulls in a chord Reynolds number of 35,000, an L/D ol 22.4, and a minimum sinking speed ol 0.74ft/sec. ln still air from a 164 ft. launch, the time to descend would be 3.7 minutes. lt will undoubtedly take time to capitalize on this in the real world of contest flying but the direction for experimentation seems clear.

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Issue

Vol. 11 No. 1 (1987)

Section

Articles

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