The Effect of Turbulence on the Drag of Flat Plates
This is a 1937 technical report from the NASA Technical Reports Server, a government aeronautics research paper of the period, presenting measured data on how airstream turbulence affects drag on flat plates. The first picture is a scatter plot of pressure-drop ratio against percent turbulence with a fitted line rising across the range, and the second photographs the test apparatus: a small fan-like rotor, a flat disc on a rod, a dark rectangular plate, and a thin probe. A designer could take from these a plain engineering-chart vocabulary of grid axes, data points and a trend line, plus the stark, uncluttered photographic style of measuring instruments.
