Question: 1. If an aircraft of wing area S and drag coefficient CD is flying at speed V in air of density ρ, and if its single airscrew, of disc area A, produces a thrust equal to the aircraft drag, show that the speed in the slipstream is, on the basis of Froude's momentum theory,
2. A cooling fan is required to produce a stream of air 0.5 m in diameter with a speed of 3 ms-1 when operating in a region of otherwise stationary air of standard density. Assuming the stream of air to be the fully developed slipstream behind an ideal actuator disc, and ignoring mixing between the jet and the surrounding air, estimate the fan diameter and power input required.