The Royal Aircraft Establishment 4 ft x 3 ft Experimental Low Turbulence Wind Tunnel PART I.—General Flow Characteristics

摘要

The 4x3 ft Wind Tunnel was erected as a model of larger tunnels to investigate unconventional design features directed towards obtaining a high standard of flow. Diffusers of 5 deg cone angle are used, except for the rapid expansion through three wire-gauze screens up to the maximum section. The contraction ratio is 31-2 :1 and nine" screens are fitted in the maximum section. A speed control is used operating independently of the fan by mean's of a by-pass duct.nThe velocity distribution across the working-section is constant to ± per cent. The standard deviation of the velocity with time measured over a period of 50 sec is 0-03 per cent.nThe flow in the diffusers shows no tendency to separate and the velocity distribution approaching the first screen is very satisfactory.