Dynamical evolution of ripples in a wave channel

Jarno, Armelle; Brossard, J.; Marin, François

doi:10.1016/j.euromechflu.2004.02.002

Cited by 15 publications

(15 citation statements)

References 15 publications

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“…However, for the GA data (larger ripples in coarser sandy bed), ripple wavelength often remains unchanged for dA b,1/3 /dt < 0 (see GA event V). These trends agree with those from other long‐term field [e.g., Traykovski , ; Maier and Hay , ] and laboratory experiments [ Davis et al ., ; Jarno‐Druaux et al ., ; Testik et al ., 2005] that have confirmed the existence of a lag time between the onset of sediment motion and the time ripples attain equilibrium. During periods when θ wc just exceeds θ cr (see GA event II, images 19–21), ripple evolution is much slower than during periods when θ wc >> θ cr (see GA event II, images 15–18).…”

Section: Discussionmentioning

confidence: 99%

“…Under continuously changing wave conditions, the transient character of the ripples might continue for a long period. A number of laboratory and field studies have been carried out aiming at understanding ripple formation from a flat bed and the transition from one geometry to another [ Davis et al ., ; Jarno‐Druaux et al ., ; Soulsby and Whitehouse , ; Testik et al ., ; Traykovski , ]. These studies have led to the development of nonequilibrium, time‐dependent models that can predict the evolution of ripples under varying wave conditions [i.e., Soulsby and Whitehouse , ; Traykovski , ].…”

Section: Introductionmentioning

confidence: 99%

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Temporal and spatial evolution of wave‐induced ripple geometry: Regular versus irregular ripples

Nelson

Voulgaris

2014

JGR Oceans

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Concurrent observations of inner shelf near bed hydrodynamics and acoustic imagery of the seabed are used to relate wave-induced ripple geometry (wavelength and orientation) to near bed directional wave velocities. The observations were collected on the continental shelf of the South Atlantic Bight at water depths of 9.5 and 30 m off the coasts of South Carolina (median size 177 mm) and Georgia (388 mm), respectively. 2-D spectral analysis techniques are performed on the imagery to automate detection of ripple wavelength, orientation, and irregularity. Our analysis shows that ripple irregularity is a time-dependent process dependent on magnitude, direction, and duration of wave forcing. During energetic events, ripple geometry changes rapidly and the ripples align with the main wave direction. During periods of low energy, close to the critical conditions for initiation of sediment motion, ripple evolution occurs at a much slower rate often leading to irregularities such as terminations and bifurcations along the ripple crest. Under constantly changing wave direction, the rippled bed becomes highly disorganized. Six types of ripples are defined based on newly developed irregularity parameters: linear, bifurcating-linear, linear-bifurcating, bifurcating and cross, irregular, and disorganized beds. Ripple irregularity depends on the time history of the bed; ripples remain irregular until their wavelength and orientation attain a nearly equilibrium geometry. The observations collected provide significant information on the response of the seabed to wave forcing and identify processes that should be reproduced by any time-dependent ripple prediction model. Ripple irregularity can only be predicted using such timedependent models.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Temporal and spatial evolution of wave‐induced ripple geometry: Regular versus irregular ripples

Nelson

Voulgaris

2014

JGR Oceans

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“…Ripples appear either uniformly over the test section or from nucleation sites according to the flow and sediments conditions. However, ripple patterns always formed uniformly over the test section for previous tests (Jarno-Druaux & al., [3]) which were carried out with plastic powder (PolyVinyl Chloride; PVC) in the same wave flume as for present tests. Using PVC powder, a rolling grain ripple stage could be clearly characterized.…”

Section: Observation Of Ripple Pattern Formationmentioning

confidence: 99%

“…However, even for 2D patterns, the spatial variability of ripples formed by a monochromatic gravity wave of high quality in a flume suggests that statistics on distributions of ripple geometric data can give further information on ripple patterns formation (Jarno-Druaux & al. [3]).…”

Section: Introductionmentioning

confidence: 99%

Pattern formation in a granular medium excited by waves in a flume

Lebunetel-Levaslot

Jarno

Marin

2008

J. Phys.: Conf. Ser.

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This work deals with the dynamics of sand ripples which occur on a flat sandy sea bed excited with an oscillatory flow in a wave flume. The bathymetry of the bed is reported since the first stages of ripple formation with an optical technique. A statistical approach is developed to study the dynamical evolution of ripples. With an identical mobility number and different Reynolds number, two tests leading to 2D and 3D pattern formation are compared. Two stages are detected during ripple formation independently of pattern morphology. However, pattern tridimensionality can be detected with statistical tools. 2D and 3D equilibrium ripple geometric data are compared with the literature.

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“…Numerous studies have been carried out on ripple formation under waves. These studies have been performed in the field [see, e.g., Inman , 1957; Myrhaug et al , 1995; Hanes et al , 2001], in laboratory with an experimental approach [see, e.g., Kennedy and Falcon , 1965; Jarno‐Druaux et al , 2004], and in a theoretical way [see, e.g., Fredsøe and Brøker , 1983; Blondeaux , 1990; Vittori and Blondeaux , 1990]. Larger‐scale bed forms such as the offshore sand waves have wavelengths of several hundreds of meters, and their heights can rise up to 10 m. Large parts of shallow seas (as the North Sea) are covered with such bed features which are the object of intensive work [see, e.g., Németh et al , 2003].…”

Section: Introductionmentioning

confidence: 99%

Laboratory study of sand bed forms induced by solitary waves in shallow water

et al. 2005

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[1] The surface profile of water waves propagating in shoaling water approaches the solitary waveform before wave breaking. The effect of the high non-linearity of solitary waves may be very significant on bed forms induced in the nearshore zone. In this study, experiments on bed form generation beneath solitary waves are carried out in a 10-m-long flume used in resonant mode. Solitary waves are generated in shallow water on the background of a standing harmonic wave. One solitary wave (soliton) propagates in each direction of the flume on the time period of the flow, above an initially flat sandy bed. Ripples form rapidly on the bed and a strong interaction with the free surface occurs. The amplitude of the soliton and the phase shift between the soliton and the harmonic wave decrease with time, while the ripple amplitude increases. The amplitude of the harmonic wave is not affected by the ripples. The final ripple wavelength is about 1000 times the sand median diameter. Bars with superimposed ripples appear, with bar crests being positioned beneath the nodes of the standing wave, when bars form with crests beneath the antinodes of surface wave for standing waves without solitons. The Eulerian drift distribution in the flume is not affected by the propagation of solitons. We propose an energy balance for solitons propagating in shallow water above flat beds in which a term for the dissipation due to sand ripples is introduced, which defines a coefficient of interaction between solitons and ripples.

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Dynamical evolution of ripples in a wave channel

Cited by 15 publications

References 15 publications

Temporal and spatial evolution of wave‐induced ripple geometry: Regular versus irregular ripples

Temporal and spatial evolution of wave‐induced ripple geometry: Regular versus irregular ripples

Pattern formation in a granular medium excited by waves in a flume

Laboratory study of sand bed forms induced by solitary waves in shallow water

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