A Method for Reducing the Base Drag of Wings with Blunt Trailing Edge

Abstract

SummaryTo study the possibilities of reducing the base drag of profiles with a blunt trailing edge, experiments were performed in two low-speed wind-tunnels at the DFVLR-AVA, Göttingen, some on models between walls and some on rectangular wings with an aspect ratio of 2.5. The results show that the mean base pressure can be increased, and so the base drag reduced, by using a special form of the blunt trailing edge. The variation of local base pressure along the span, and the way in which this variation is influenced by the form of the trailing edge, is also shown. Some results for the total drag and lift are also indicated.

Spanwise vortex dislocation in the wake of segmented blunt trailing edge

“…1(b)). These dimensions were found near optimum by Tanner (1972). The trapezoidal prismatic block was symmetrical about the transverse (y) axis with its acute angle a ¼ 451 rendering the minor and major sides of 40 mm ( ¼2h) and 80 mm ( ¼4h), respectively, along the spanwise (z) axis.…”

“…Investigator Base drag reduction (%) Rectangular segmented trailing edge Tanner (1972) 35 Gai and Sharma (1981) and Sharma (1988) 23 Petrusma and Gai (1994) 38…”

“…M-shape segmented trailing edge Tanner (1972) 64 Gai and Sharma (1981) and Sharma (1988) 58 Rodriguez (1991) 41…”

“…Introduction of three dimensionality in the near wake of a two dimensional blunt trailing edge aerofoil by means of certain geometric cutouts along the span in the trailing edge has been found to be an effective method to reduce the base drag (Gai and Sharma, 1981;Petrusma and Gai, 1989, 1992Rodriguez, 1991;Sharma, 1988;Tanner, 1972). The width and depth of these cutouts of the segmented trailing edge were of the order of about 4 base height along the span and 2 base height along the chord.…”

Bluff body wakes with free, fixed, and discontinuous separation at low Reynolds numbers and low aspect ratio

“…Aerofoils with segmented blunt trailing edges have been known to achieve significant base pressure recovery compared to the plain blunt trailing edges (Tanner 1972, Pollock 1972, Petrusma 1990. The basic mechanism which results in an increased base pressure is that the segmented trailing edge offers a discontinuous separation line which breaks up the two dimensional vortex shedding by imposing three dimensional disturbances.…”