Vorticity dynamics in an oscillatory flow over a rippled bed

Blondeaux, Paolo; Vittori, Giovanna

doi:10.1017/s0022112091002380

Cited by 81 publications

(55 citation statements)

References 30 publications

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“…[81] The model has been validated for current only conditions, for laminar and turbulent motion, in order to check the reliability of the results using known literature case studies, and for wave only conditions, comparing the results with the ones of Scandura [1999] and of Blondeaux and Vittori [1991], in terms of vorticity lines. Being the comparison satisfactory, the wave plus current conditions were first run on a flat bottom and then on a rippled bed.…”

Section: Faraci Et Al: Waves Plus Currents At Right Anglementioning

confidence: 99%

Waves plus currents at a right angle: The rippled bed case

2008

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[1] The present paper deals with wave plus current flow over a fixed rippled bed. More precisely, modifications of the current profiles due to the superimposition of orthogonal cylindrical waves have been investigated experimentally. Since the experimental setup permitted only the wave dominated regime to be investigated (i.e., the regime where orbital velocity is larger than current velocity), also a numerical k-e turbulence closure model has been developed in order to study a wider range of parameters, thus including the current dominated regime (i.e., where current velocity is larger than wave orbital one). In both cases a different response with respect to the flat bed case has been found. Indeed, in the flat bed case laminar wave boundary layers in a wave dominated regime induce a decrease in bottom shear stresses, while the presence of a rippled bed behaves as a macroroughness, which causes the wave boundary layer to become turbulent and therefore the current velocity near the bottom to be smaller than the one in the case of current only, with a consequent increase in the current bottom roughness.

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Section: Faraci Et Al: Waves Plus Currents At Right Anglementioning

confidence: 99%

Waves plus currents at a right angle: The rippled bed case

2008

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“…Hence, the growth/decay of the bottom waviness is the result of a competition between these two effects. The process that leads to the appearance of wave ripples and their time development was studied and quantified by means of linear and weakly nonlinear analyses [13][14][15][16][17][18][19][20], and the results are summarized in the review papers of [21,22]. Table 1.…”

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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“…It is noted that there are many independent length scales in the oscillatory flow over a rippled bed, and the length scale involved in the definition of flow parameters is different among researchers. In the Reynolds number, for example, the length UT / 2 π was used in [ 8 , 9 ]; Stokes layer thickness, defined as δ = √ νT /π, was used by Blondeaux and Vittori [ 10 ]; ripple wavelength λ was used by Du Toit and Sleath [ 3 ].…”

Section: Introductionmentioning

confidence: 99%