Extended Data Fig. 2: Effects of different aspects of grain shape on fluid drag coefficient.

The measured drag coefficient of a grain settling in still water, C_Dsettle, relative to the calculated drag coefficient of the volume-equivalent sphere, C_o, as a function of the Corey shape factor, a measure of gross grain shape. Coloured points show the materials used in our flume experiments and the additional materials in Extended Data Fig. 3a–e. Grey lines are fits to a large compilation³² of single-grain settling experiments that have been sorted by grain angularity, a measure of small-scale grain shape. Sketches in key show idealized grains of different angularity. Red dashed line is the trend 1/S_f for comparison. Error bars show one standard error of the mean.