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Title: The mechanics of the motion of discrete spherical bottom sediment particles due to shoaling waves
Authors: Massachusetts Institute of Technology. Hydrodynamics Laboratory
United States. Army. Office of the Chief of Engineers
Eagleson, Peter S.
Dean, Robert G. (Robert George), 1930-2015
Peralta, L. A.
Keywords: Beach models
Sedimentation and deposition
Mathematical models
Sediment sorting
Publisher: United States, Beach Erosion Board
Engineer Research and Development Center (U.S.)
Series/Report no.: Technical memorandum (United States. Beach Erosion Board) ; no. 104.
Description: Technical Memorandum
Abstract: This report represents a continuation and re-evaluation of data from a previous investigation into the mechanics of the processes by which beach sediments are sorted selectively when acted upon by shoaling waves. The experimental facilities consisted of a 100-foot long, 2 and 1/2 foot wide and 3 foot deep glass-walled wave channel which contained an artificially roughened, fixed, plane beach of variable slope in one end. Waves were generated at the other end by a horizontally reciprocating piston actuated by a hydraulic servomechanism with continuously variable speed and stroke. The incipient and net motions of discrete spherical sediment particles 2 to 6 mm in diameter with specific gravities in the range of 1.19 to 2.65 were studied statistically on smooth and roughened surfaces of zero, 1 to 22.4 and 1 to 14.8 slope. Two seperate beach sand roughnesses were used throughout, k = 0.79mm and k = 1.83mm. Test conditions for the net motion studies comprised nine waves in the range of equivalent deep water steepness 0.001 < HoLo < 0.06. A theoretical analysis is presented which yields an equation for the net velocity of a given spherical sediment particle as a function of the resistance coefficient, ~, the fluid mass transport velocity at the elevation of the particle center and the beach slope, ~ . The equation is verified by laboratory measurements and is extended by means of an approximate determination of the bottom boundary layer characteristics to the prediction of the equilibrium relationship between local wave characteristics, beach slope and median particle diameter found on natural beaches. Incipient motion data are also correlated by means of a derived resistance coefficient as a function of particle Reynolds number. Note: The symbol ~ is used to represent scientific and mathematical symbols this character set was unable to render. The downloaded file will contain the missing symbols.
Rights: Approved for Public Release, Distribution is Unlimited
Appears in Collections:Technical Memorandum

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