Design and calibration tests of a 5.5 in. square supersonic wind tunnel

Abstract

The main design features of the wind tunnel are described and results are given of the investigations carried out to determine:- (i) the minimum pressure ratio required to operate the wind tunnel at Mach numbers up to 3.5, and (ii) the uniformity of the velocity distribution in the working section at Mach numbers of 1.57, 1.88, 2.48, 2.85, 3.25 and 3.5. It was found that the tunnel pressure recovery can be appreciably increased by means of a contraction ('second throat') located between the working section and subsonic diffuser. All nozzles tested were designed with short throats and expansion profiles with the maximum angles of expansion for the given exit Mach number. The axial variation of Mach number over selected intervals of working section (not smaller than 5 in.) was found to be of the order of ± 1.0 per cent. It was found that condensation in the wind tunnel nozzle (run with atmospheric air), has a detrimental effect on the velocity distribution in the working section, particularly at small Mach numbers.