Small Scale Ripple Superimposed on Large Scale Ripple
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Ripple marks
Ripple marks
Dimensionless quantity
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The following paper contains an account of experiments and observations on the formation of ripple-mark in sand. The first section is devoted to experiments on the general conditions under which ripple-mark is formed, and especially on the mode of formation and maintenance of irregular ripples by currents. In the second section it is shown that regular ripple-mark in sand is due to a complex arrangement of vortices in oscillating water; and the last section gives some account of the views of certain recent observers in this field, and a discussion of some phenomena in the vortex motion of air and water.
Section (typography)
Ripple marks
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The object of the investigation was to determine how ripple-mark started in perfectly smooth sand, apart from accidental variations of surface friction; how the ripples grew; how the amplitude and depth of the water affected them; and whether there was any connection between ripple-mark and kindred phenomena, such as the dust figures in a Kundt’s tube. In the course of the investigation the causes, form, and mode of action of “ripple vortices” in the water were determined, and the fact that no vortices of this kind can form in a current flowing steadily in one direction over an obstacle was demonstrated, both theoretically and practically. Also many minor details came to light, such as the fact that each ripple is continually travelling, as a whole, and why it does so.
Ripple marks
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Ripple marks,a surface structure,occur in any area where there is water flowing (no matter what environment it is).Therefore,ripple marks do not indicate facies but directions of water flowing.Outside events such as floods and turbidity currents can form ripple marks of different types.In some gulleys over a flood land in the upper reaches of the Yellow River,modern subaerial ripple marks are discovered.The gulleys are about 200 m away from the flood land.Due to the actions of seasonal water flowing,there is a lush growth of grass at the outlets,and between the grass,appears a wide open area where there are a great number of modern asymmetric ripple marks.Substrate of the asymmetric ripple marks is grayish yellow subsilty soil overlain by purple and thin (about 0.5 cm thick)subsilty layer,which is closely related to the formation of the asymmetric ripple marks. The formation of such asymmetric ripple marks is based not only on open and flat areas but also on outside flood events.And as for those of continental basins,climatic conditions are always the leading factor for the sizes,scales and configurations of ripple marks.Ripple marks in deep-sea environments have various types,such as curved,linear,crescentic,tongue- and fork-like.These ripple marks often coexist with CD sequences of turbidity currents.The deep-sea ripples mainly develop from the foot of a slope to a continental rise,belonging to smooth landform.The ripple marks go in direct proportion to the thickness of turbidite and result from the dragging of low-density turbidity currents on the bed sand.In other words,the deep-sea ripples are controlled by the scales and intensities of the turbidity currents.And in land environments,the development of ripple marks is usually controlled by ancient climate.Wet climate often causes the levels of rivers and lakes to rise.And as a result of that,a lot of ripple marks are developed.
Ripple marks
Subaerial
Turbidity current
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Observation of development of ripple marks on water channel bottom by use of colored sand particles.
Ripple marks developed on the sea bottom were reproduced in a circulating water channel. Process of development of ripple marks was observed by means of colored sand particles. From upstream side the ripple marks develop progressively with time. It is shown further that a fence at the upstream side suppresses the development of the ripple marks.
Ripple marks
Colored
Fence (mathematics)
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SUMMARY A mechanical analog has been designed, constructed, and operated to produce a variety of ripple marks. Ripple‐mark maintenance has been studied in a wave tank, in an experimental flume, on tidal flats, and on dune fields.
Ripple marks
Flume
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Laboratory experiments have demonstrated that an essential factor in forming appreciable deposits of ripple–laminated sand is the introduction of an abundance of sediment into an area of ripple movement. A sequence of ripple laminae developed under such conditions changes both laterally and vertically as the result of changing stream regime during the time of deposition. Ripple laminae formed from stream currents show few or no important differences from those developed by waves with a forward component, but both types show many variations in size and shape of ripple profiles, caused by differences in water depth, wave or current strength,...
Lamination
Ripple marks
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Ripple marks
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A series of wave-flume experiments was performed to examine ripple geometry, development, and migration under partially standing waves for five different intensities of wave reflection. The present experiments showed the cross-shore variation of the development and geometry of bedforms corresponding to the position of nodes and antinodes. The ripple field tended to initiate under nodes and spread from nodes to antinodes. The local-mean ripple spacings were the largest under nodes and the smallest under antinodes. The difference of the ripple development and the ripple spacing between nodes and antinodes became more pronounced with increasing the intensity of wave reflection. The local-mean ripple spacings in the present experiments correspond approximately with those predicted by Nielsen's (1979, 1981) empirical formula. The trend of sediment transport predicted by ripple migration is consistent with the bed profiles at the end of each run. The geometry, development, and migration of ripples are a possible clue for understanding the cross-shore variation in local hydraulic conditions and mass sediment transport under partially standing waves.
Ripple marks
Reflection
Flume
Standing wave
Bedform
Wave flume
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An experimental investigation of bedforms generated by the currents is carried out in a flume. Tests with different flow conditions are performed on sand beds. Figures and data obtained in the study are analyzed and the mechanism of ripple formation is discussed as well in this paper.
Flume
Bedform
Ripple marks
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