Water-power; an outline of the development and application of the energy of flowing water . horizontal line mi,sometimes by an inclined line. Down-stream from d the damis constructed according to the nature of the ground. Forrock of moderate hardness the surface would continue level forsome little distance and terminate in a vertical face. Thisvertical face is usually rendered necessary by the irregularshape of the bed. If the bed were level and smooth, thedown-stream face could join it by a curve having its tangent-point at d, but this is usually impossible. Sometimes the toeis so formed as t
Water-power; an outline of the development and application of the energy of flowing water . horizontal line mi,sometimes by an inclined line. Down-stream from d the damis constructed according to the nature of the ground. Forrock of moderate hardness the surface would continue level forsome little distance and terminate in a vertical face. Thisvertical face is usually rendered necessary by the irregularshape of the bed. If the bed were level and smooth, thedown-stream face could join it by a curve having its tangent-point at d, but this is usually impossible. Sometimes the toeis so formed as to give an upward direction to the water, as at 34 DAMS FOR WATER-POWER. Fig. I5«, in the expectation that the abrasive action is therebycarried farther from the dam. It may be doubted if any realadvantage results from this arrangement. It gives a widerleap to the stream and tends to diminish the velocity withwhich it strikes the bottom. It gives greater opportunityfor the development of horizontal eddies under the stream, andexposes the toe in greater measure to the impact of floating. K -„/ Fin. 15. Fig. 15a. bodies carried by the reverse current. In high water, when the down-stream surface comes well up on the curved face of the dam. such refinements of construction cut no figure, unless it be the following: Logs and blocks of ice, in passing the curved surface of the dam, are subject to a centrifugal force which causes them to hug the surface. This action is not necessaril)-injurious between b and c/, where there is no danger of dislodging a stone. It is liable to act injuriously upon the exterior stones of the toe. Suppose a 30-foot dam and assume a radius of 20 feet in the curve of the toe. A hcav\ body would reach this curve with a velocity of something like 44 feet per second and would exert thereon, while passing, a W 44 X 44 pressure of— X ^ = ^^ X 3, , a pressure of three ^ 20 £>AMS CURVED IN CROSS-SECTION. ,35 times its normal weight. The frictional pull
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecthydraulicengineering
