Experiments on the flow of water from a reservoir through an open horizontal channel II. The formation of hydraulic jumps

The stream, on which the experiments were carried out, was produced by leading water from a reservoir through a rectangular contraction into an open channel that was slightly inclined downwards. By means of a hinged planing plate resting on the surface, single waves and wave trains fixed in space were formed ahead of the plate, and the required loads on the plate were measured. A more systematic study of smooth and broken undular jumps was made with a weir at the channel outlet providing the necessary obstruction. The boundary between these two types of jump was at F1 = 1·26, F1 being the Froude number of the approaching stream. The second type decayed into the wholly turbulent jump at about F1 = 1·75. Little difference was found between the heights of the leading wave in the smooth undular jumps and the theoretical heights of a solitary wave formed at the same Froude number, and Rayleigh’s classical theory (1914) gave a fair approximation to the mean depth in the undular trains of waves.