Calibration of the Royal Aircraft Establishment 24-ft wind tunnel

Abstract

Evidence from several check experiments indicated that the results of the preliminary calibration of 1935 were in error. The object of the described experiment was to investigate this and to calibrate the wind tunnel in greater detail than previously. The velocity distribution across the jet in three planes has been found at several tunnel speeds. The distribution of static pressure throughout the jet and the relation between the dynamic head at various positions in the tunnel and the hole-in-side pressure has been investigated. A complete list of all previous calibrations together with results and reasons for the discrepancies is included. A new tunnel calibration is given in Tables 1 and 2. The plane of reference is taken as 12.5 ft from the jet face, and the mean velocity over the section is greater than the standard value used up to the present by about ½ per cent at high speeds and 2 per cent at low speeds. The mean velocity falls as the jet face is approached, and a correction factor for this is given in Table 2. The revised corrections will be incorporated in all reports issued after 30th June, 1942.