Electrical news and engineering . -scouring velocity. The minimum width of the rock sectionwas fixed by the type of electric shovel used for excavatingthis portion of the canal and was placed at 48 feet. The problem thus resolved itself into selecting the bestproportions for the trapezoidal earth section and the bestdepth and slope for the 48 foot rock section. The procedurein the latter case is the one that will be described. It is, of Course, possible to design any number of canals4S feet wide, but with depth and slope varying so that allwill give the same discharge at low water. For a low v
Electrical news and engineering . -scouring velocity. The minimum width of the rock sectionwas fixed by the type of electric shovel used for excavatingthis portion of the canal and was placed at 48 feet. The problem thus resolved itself into selecting the bestproportions for the trapezoidal earth section and the bestdepth and slope for the 48 foot rock section. The procedurein the latter case is the one that will be described. It is, of Course, possible to design any number of canals4S feet wide, but with depth and slope varying so that allwill give the same discharge at low water. For a low vel-ocity the wetted cross-section must be deep but its slope maybe moderate. For a high velocity the depth of the wettedcross-section will be small but the slope may be so greatthat the depth of the cut at the down-stream end may begreater and the total cost of excavating greater than for thelow velocity design. The procedure in determining the economic depth wasas follows: First, the design of a number of cross sections for vel-. Profile of Qucenston-Chippawa pov of river section THE ELECTRICAL NEWS ocities of 3, 4, 5, etc., feet per second, the determination ofthe requisite slope of the bed in each case to give the fullload discharge with uniform flow, and the determination ofthe variation in cost of these canals with low water velocity. Second, the determination of the friction loss in each ofthese canals with the river stage at its mean value. Thisfriction loss represented so much lost power, which was, ofcourse, small in amount for the lesser low water velocities,and greater as the low water velocity increased up to a cer-tain point. Third, the plotting of the differential curves for items 1and 2 thus showing the variation in delta cost with lowwater velocity and the variation in delta power with lowwater velocity. From these two differential curves a thirdcurve can thus be obtained giving the value of delta-cost bydelta-power plotted against low-water velocity. Thus there
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