Calibration of the R.A.E. No. 18 (9" x 9") Supersonic Wind Tunnel. Part II:- Tests at Atmospheric Stagnation Pressure

Abstract

This report presents distributions of Mach number in the empty working section of the R.A.E. No. 18 (9" x 9") Supersonic Wind Tunnel at nominal Mach numbers of 1.4, 1.5, 1.6, 1.8 and 1.9, for condensation-free flow at atmospheric stagnation pressure and at a stagnation temperature cf 35°C. The results confirm that the accuracy of the tests is of the order predicted in Part I. The mean measured Mach numbers are 1.41, 1.51 1.61, 1.81 and 1.91 when calculated from values of pitot and stagnation pressures. The major contributions to the non-uniformity of the flow are from the disturbances which arise from the junctions of the windows with the side walls of the tunnel; these disturbances are of the order of + or -0.015 in Mach number, whilst the maximum gradual variations in the flow caused by other sources are of the order of + or -0.010. An indication cf the boundaries of the working section for each Mach number is given. Note (August, 1953) Since the accounts of the calibration contained in Parts I and II were written (Part I: December, 1951 Part II: March, 1952), the tunnel equipment has been greatly improved and its limitations are no longer as severe as those described here; the improvements do not invalidate the present results, but no further detailed calibration measurements have been made.