NACA-RM-A52B20

Abstract

INTRODUCTION <br>An investigation of the effects of Mach number and Reynolds number on the aerodynamic characteristics of several 12-percent-thick wings having 35&#176; of sweepback and various amounts of camber has been reported in reference 1. The results of this investigation indicate that an abrupt decrease of lift-curve slope accompanied by a large reduction of static longitudinal stability occurred at the design lift coefficient at a Reynolds number of 2,000,000 when the Mach number for drag divergence was exceeded. Similar phenomena have been reported in reference 2 which presents results of tests at a Reynolds number of about 600,000 of several wings having 45&#176; of sweepback and the NACA 63₁A012 section in planes parallel to the plane of symmetry. This reduction of static longitudinal stability is contrary to previous results from tests of swept-back wings having sections less than 12 percent thick. (See, for example, references 3 and 4.) The results of reference 1 also indicate the effects of Reynolds number on the aerodynamic characteristics of the wings at low Mach numbers to be large. <br>In order to determine the nature of the changes in loading which resulted in the above phenomena, a duplicate of one of the semispan models of reference 1 was constructed. This model was equipped with flush orifices for the measurement of surface pressures. High-speed tests were conducted in the Ames 12-foot pressure wind tunnel and in the Ames 16-foot high-speed wind tunnel in order that the effect of a variation of Reynolds number from 2,000,000 to about 4,500,000 could be assessed at high Mach numbers. Low-speed tests were conducted in the 12-foot wind tunnel over the same range of Reynolds numbers as reported in reference 1.