Study of open jet wind tunnel cones
This is a 1927 NACA Technical Note from the National Advisory Committee for Aeronautics, a government research report on open jet wind tunnel exit cones, written for aeronautical engineers and researchers. Its pictures are plain black-and-white photographs and line charts: photographs of smoke or flow patterns through differently flared cones, a rotated view of a wind tunnel apparatus, and a grid graph of measured curves. A designer might take from them the stark tonal contrast of smoky airflow and the clean, gridded technical chart style.
