Chemical solids as diffusible coating films for visual indications of boundary-layer transition in air and water

Abstract

Experimental investigations have been made on various chemical solids as diffusible coating films for visual indicatien of boundary-layer transition in air and water. Originally, the method was applicable only at low speeds in wind tunnels and water tanks, and the indications were somewhat transient. More durable coating materials have now been made available, admitting of use at subsonic and supersonic wind-tunnel speeds from 30 to 1350 m.p.h., and at ship-hull speeds from 26 to 20 kt. The method has also proved capable of extension to aircraft in flight at speeds from 100 to 445 m.p.h, at temperatures down to -- 22 deg C and at altitudes up to 20,000 ft. The diffusible solid-coating method, with its advantages of autographic indication and simplicity and rapidity of operation, has thus become a versatiie technique in investigations on fluid flow in aerodynamics and hydrodynamics.