The evolution of a duned bed from an initially flat bed was observed in a large water tunnel in which water moved over a sand bed with simple harmonic motion. Bed forms were observed to be of two types, (1) rolling‐grain and (2) vortex, which are called ripples and dunes, respectively. Ripples are the initial transient bed forms that are replaced by dunes. Ripples formed spontaneously when the water‐motion amplitude was sufficiently large. Ripples can be induced to form at lesser water‐motion amplitudes by placing an obstruction on the otherwise flat bed. The history of a duned bed was observed and is described from birth to equilibrium.
The force components on an oscillating sphere in a fluid medium were studied by experimental means. These force components on the oscillating sphere were separated into the inertial effective force and the dissipative (shear) force. In order to accomplish this experimental program, the writer assumed that the sphere motion was approximately simple harmonic motion, and he analyzed the data as if the motion were exactly simple harmonic motion.
The experimental results were applied to an allied problem of a sphere in an oscillating fluid. The experimental results, as applied to this problem, were found to compare with the data of an experiment performed in Germany in about 1920. Extending the analysis further, the writer presents a simple analysis of the diffusion characteristics of suspended sediment in water.
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