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Isbash method, calculation diameter of stone (fps)

작성자 Uploader : ezetc 작성일 Upload Date: 2016-03-19변경일 Update Date: 2016-03-19조회수 View : 684

According to Isbash the basic equation for the movement of stone in flowing water can be written as:

V = C[2g*((γs-γw)/γw)]^(1/2) * (D)^(1/2)
D = (γw*V^2)/(C^2*2g*(γs-γw))

V  = average flow velocity, fps
C  = a coefficient (for sliding;0.86, for rolling or overturning;1.20)
g  = acceleration of gravity, ft/sec^2
γs = specific weight of stone, lb/ft^3
γw = specific weight of water, lb/ft^3
D  = stone diameter, ft

The Isbash coefficients are from tests with essentially no boundary layer development
and the average flow velocities are representative of the velocity against stone. When the stone movement resulted by sliding, a coefficient of 0.86 was obtained. When movement was effected by rolling or overturning, a Coefficient of 1.20 resulted. Extensive U. S. Army Engineer Waterways Experiment Station laboratory testing for the design of riprap below stilling basins indicates that the coefficient of 0.86 should be used with the average flow velocity over the end sill for sizing stilling basin riprap because of the excessively high turbulence level in the flow.


*** 참고문헌[References] ***

HYDRAULIC DESIGN CRITERIA, SHEET 712-1, STONE STABILITY, VELOCITY VS STONE DIAMETER
D = (γw*V^2)/(C^2*2*g*(γs-γw))
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변수명 Variable 변수값 Value 변 수 설 명 Description of the variable


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