A turbulence indicator utilizing the diffusion of heat
A 1936 technical report from the NASA Technical Reports Server describing a turbulence indicator that works by heat diffusion, probably aimed at aeronautical engineers and researchers. The single picture is a line drawing of the apparatus, with lettered parts A to D, dimension lines marked 10½ inches, 3 inches and 8½ inches, and a tunnel floor mounting at the base. A designer could take its clean, labelled mechanical-diagram style: thin black strokes, dimension callouts and tidy lettering for technical infographics.
