On Rolling-Grain Ripples

Sleath, J. F. A.

doi:10.1080/00221687609499689

Cited by 121 publications

(67 citation statements)

References 3 publications

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“…As pointed out by Hulscher (1996), Gerkema (2000) and other authors, the process which gives rise to the formation of sand waves is similar to that originating dunes in rivers (Engelund, 1970) or to that causing the appearance of sea ripples under sea waves (Sleath, 1976;Blondeaux, 1990). In fact, the interaction of the oscillatory tidal current with a bottom perturbation gives rise to a steady streaming in the form of recirculating cells.…”

Section: Introductionmentioning

confidence: 82%

The morphodynamics of tidal sand waves: A model overview

Besio¹,

Blondeaux²,

Brocchini³

et al. 2008

Coastal Engineering

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This paper reviews recent theoretical studies of sand waves which are rhythmic large-scale bedforms observed in the continental shelf far from the near-shore region. Emphasis is given to the investigations carried out in the framework of the EU research project HUMOR. First, the results of linear morphodynamic stability analyses are described, which allow to understand the initial behavior of the sand waves. Hence, indications on the physical processes controlling the appearance and development of sand waves are obtained along with quantitative predictions of the wavelength of sand waves and of their migration speed. Then, nonlinear models are described which are used to predict the equilibrium profile of sand waves and their interaction with human interventions like sand extraction or the construction of pipelines. Finally, we discuss an analytical model which describes how the sand wave instability behaves when it is triggered locally; this leads to the generation, growth and expansion of a so-called sand wave packet.

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Section: Introductionmentioning

confidence: 82%

The morphodynamics of tidal sand waves: A model overview

Besio¹,

Blondeaux²,

Brocchini³

et al. 2008

Coastal Engineering

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“…As pointed out by Hulscher et al (1993), de Swart et al (1995), Hulscher (1996a,b), and later discussed by Gerkema (2000), Komarova and Hulscher (2000) and Besio et al (2003a), the process which leads to the formation of these bedforms is similar to that originating sea ripples under sea gravity waves (Sleath 1976;Blondeaux 1990Blondeaux , 2001Blondeaux and Vittori 1999). In fact, the interaction of the oscillatory tidal flow with bottom perturbations gives rise to a steady streaming in the form of recirculating cells.…”

Section: Introductionmentioning

confidence: 85%

Migrating sand waves

et al. 2003

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A simple mathematical model is described, which reproduces the major features of sand waves' appearance and growth and in particular predicts their migration speed. The model is based on the linear stability analysis of the flat configuration of the sea bottom subject to tidal currents. Attention is focused on the prediction of the complex growth rate Gamma that bottom perturbations undergo because of both oscillatory fluid motions and residual currents. While the real part Gammar of Gamma controls the amplification or decay of the amplitude of the bedforms, the imaginary part Gammai is related to their migration speed. Previous works on the migration of the sand waves (Németh etblankal. 2002) consider a forcing tide made up by the M2 constituent (oscillatory period equal to 12 h) plus the residual current Z0 and predict always a downcurrent migration of the bedforms. However, field cases exist of upcurrent-migrating sand waves (downcurrent/upcurrent-migrating sand waves mean bedforms moving in the direction of the steady residual tidal current or in the opposite direction, respectively). The inclusion of a tide constituent characterized by a period of 6 h (M4) is the main novelty of the present work, which allows for the prediction of the migration of sand waves against the residual current Z0. Indeed, the M4 tide constituent, as does also the residual current Z0, breaks the symmetry of the problem forced only by the M2 tide constituent, and induces sand-wave migration. The model proposed by Besio etblankal. (2003a) forms the basis for the present analysis. Previous works on the subject (Gerkema 2000; Hulscher 1996a,b; Komarova and Hulscher 2000) are thus improved by using a new solution procedure (Besio etblankal. 2003a) which allows for a more accurate evaluation of the growth rate for arbitrary values of the parameter r, which is the ratio between the horizontal tidal excursion and the perturbation wavelength

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“…Moreover, comparing the data of wave ripples with those of wave-current/current ripples, it appears that a unidirectional current unrelated to waves affects ripple asymmetry in much the same way as wave-induced mass transport. The mechanism that controls the formation of wave ripples is well understood, because it was shown that the interaction between the oscillatory flow induced close to the bottom by sea waves and a wavy perturbation of the erodible bottom profile gives rise to a steady streaming, which consists of recirculating cells [11,12]. The strength of the steady velocity component and the shape of the recirculating cells depend on the characteristics of both the sea wave and the bedforms.…”

Section: Introductionmentioning

confidence: 99%

A theoretical model of asymmetric wave ripples

Blondeaux

Foti

Vittori

2015

Phil. Trans. R. Soc. A.

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The time development of ripples under sea waves is investigated by means of the weakly nonlinear stability analysis of a flat sandy bottom subjected to the viscous oscillatory flow that is present in the boundary layer at the bottom of propagating sea waves. Second-order effects in the wave steepness are considered, to take into account the presence of the steady drift generated by the surface waves. Hence, the work of Vittori & Blondeaux (1990 J. Fluid Mech. 218, 19-39 (doi:10.1017/S002211209000091X)) is extended by considering steeper waves and/or less deep waters. As shown by the linear analysis of Blondeaux et al. (2000 Eur. J. Mech. B 19, 285-301 (doi:10.1016/S0997-7546(90)00106-I)), because of the presence of a steady velocity component in the direction of wave propagation, ripples migrate at a constant rate that depends on sediment and wave characteristics. The weakly nonlinear analysis shows that the ripple profile is no longer symmetric with respect to ripple crests and troughs and the symmetry index is computed as a function of the parameters of the problem. In particular, a relationship is determined between the symmetry index and the strength of the steady drift. A fair agreement between model results and laboratory data is obtained, albeit further data and analyses are necessary to determine the behaviour of vortex ripples and to be conclusive

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On Rolling-Grain Ripples

Cited by 121 publications

References 3 publications

The morphodynamics of tidal sand waves: A model overview

The morphodynamics of tidal sand waves: A model overview

Migrating sand waves

A theoretical model of asymmetric wave ripples

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