VITTORI , Giovanna

This paper describes the dynamics of a mathematical model for the mobile barriers designed to close the tidal inlets of the Venice Lagoon and to defend the city from recurrent high waters. The barriers consist of a large number of steel caissons (hereafter referred to as gates) connected to the seabed with hinges. The gates usually rest...

The interaction between sea waves and the oscillating gates designed to close the three inlets of Venice lagoon and to protect the city from the phenomenon of high waters is studied. Previous studies of this topic, which considered monochromatic waves, are extended to consider random waves characterized by a narrowband wave spectrum, such that...

This paper examines the oscillatory flow induced by progressive gravity waves near a sea bottom covered with three-dimensional ripples. Previous works on the subject, in which only two-dimensional bottom waviness were considered, are thus extended. By assuming small values of the ratio between ripple amplitude and the thickness of the bottom...

he non-linear viscous oscillatory flow over a wavy wall of small amplitude is determined. The solution holds for arbitrary values of a /L (a is the amplitude of fluid oscillations near the wall and L is the wavelength of wall perturbation); previous works of Lyne [1], Kaneko and Honji [2] on the subject are thus extended. An independent...

A simulation of the turbulent flow and sediment dynamics in the boundary layer originated close to the seabed by a first-order Stokes wave is performed. The flow field is obtained by the numerical integration of Navier-Stokes and continuity equations while sediment trajectories are computed via a simplified model that assumes a one-way...

A model is presented to determine the wavelength, the height and, more importantly, the migration speed of sand waves (also named tidal dunes) in shallow tidal seas. The model is based on a linear stability analysis and predicts the growth and migration of the fastest growing mode of a random perturbation of the flat sea bed forced by tidal...

The possible excitation of synchronous edge waves by a monocromatic wave normally approaching a plane beach is studied. Use is made of the full three-dimensional water wave theory but only beach angles β = π/(2N), where N is an integer, are considered. A weakly nonlinear stability analysis is used to investigate the interaction of subharmonic,...

The two-dimensional oscillatory flow around a circular cylinder is analyzed by means of the numerical approach described in Justesen J. Fluid Mech. 222, 157 (1991). For a fixed value of the ratio between the Stokes viscous thickness and the radius of the cylinder section, when the Reynolds number assumes low values, the flow is periodic and...

A fully three-dimensional model for the generation and evolution of tidal sand waves and sand banks from bottom perturbations of a flat seabed subject to tidal currents is proposed. The basic flow, comprehensive of Coriolis effects, is completely resolved in the vertical direction from the sea bed up to the free surface and describes both...

Tidal sand waves, also named tidal dunes, are large scale bedforms generated by the growth of perturbations of the sea bottom driven by tidal currents. Indeed, the interaction of an oscillatory tidal current with a bottom waviness gives rise to steady recirculating cells which tend to drag the sediment from the troughs towards the crests of...

Field surveys show the existence of morphological patterns (named bed load sheets in fluvial enviroments and sorted bedforms in coastal environments) which consist of alternate bands of coarse and fine sediments and are characterized by a negligible spatial variation of the bottom elevation. Previous analyses show that these bottom patterns are...

Numerical simulations of Navier–Stokes equations are performed to study the flow originated by an oscillating pressure gradient close to a wall characterized by small imperfections. The scenario of transition from the laminar to the turbulent regime is investigated and the results are interpreted in the light of existing analytical theories....

The transition process which leads the oscillatory flow over a wavy wall from a periodic behavior to chaos is studied by means of the numerical algorithm described by Blondeaux and Vittori [J. Fluid Mech. 226, 257 (1991)]. By increasing the Reynolds number, it has been found that the flow experiences an infinite sequence of period doublings...

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To investigate the formation of the sand waves generated by tide propagation, the stability of the flat sea bottom forced by tidal currents is often analyzed. Both quasi-steady and unsteady approaches are used. The quasi-steady approaches consider a steady current characterized by a slowly varying strength such that the time t is...

A study of the oscillatory incompressible flow close to a wall covered with fixed rigid spheres is carried out by numerical means to provide information on unsteady flows over a rough wall. The simulations are carried out for two bottom configurations, characterized by different values of the diameter of the spheres and different values of the...

The results of direct numerical simulations of the boundary layer generated at the bottom of a solitary wave are described. The numerical results, which agree with the laboratory measurements of Sumer et al. (2010) show that the flow regime in the boundary layer can be laminar, laminar with coherent vortices and turbulent. The average...

A morphological model to predict the formation of tidal dunes (sand waves) and their migration is described. The analysis assumes that the appearance of the bedforms is due to the growth of the most unstable component of an initially random perturbation of small amplitude, forced by a uniform tidal flow. Results are presented for a...

The idealized model of Besio et al. (2006) is used to predict the wavelength of tidal dunes (sand waves) generated by tidal currents in estuaries and shallow seas. Then, the predictions are analysed and a formula is proposed to estimate the wavelength of tidal dunes as a function of the parameters of the problem. The wavelength of the dunes...