334 



HYDRAULICS AND ITS APPLICATIONS 



the results of gaugings on the experimental channel of the Cornell 

 University. 1 



This is of rectangular section, with concrete sides and bottom having a 

 slope of 1 in 500, and has a width of 16 feet. Velocity measurements 

 were made in eight verticals in a cross-section by means of current meters. 



The curves in Figs. 147 and 148 show the variations of velocity in a 

 vertical plane in typical of these experiments, each plotted point giving 

 the mean of all eight observations at that depth in the cross-section. 



The effect of a large ratio of width to depth in raising the filament of 

 maximum velocity is evident from a comparison of the curves of Fig. 147 



1 





1-0 12 14 1-6 

 Velocity. Ft. Per Sec. 

 FIG. 148. 



/a 



2-0 2-2 



and of Fig. 148, while the effect of an increased velocity of flow in raising 

 the filament is evident from a comparison of the several curves of Fig. 148. 

 The depression of this filament of maximum velocity is mainly due 

 to the action of the sides of the channel. Frictional losses at the sides 

 reduce the energy and thus the head of the water in their neighbourhood, 

 with the result that the surface level at the sides is lower than near the 

 centre of the stream, and the cross-sectional profile of the water surface 

 is a curve concave to the bed. Owing to this super-elevation of the 

 water near the centre and to its tendency to find its own level, transverse 

 currents are set up which travel downwards near the centre of the 

 stream ; outwards along the bottom to either bank, upwards along the 

 sides, and, for permanence of regime, inwards along and near the surface. 



1 U. S. Geological Survey, Water Supply and Irrigation Papers, No. 95, pp, 76 and 77. 



