Giovanni Cannata

Compatibility of Reservoir Sediment Flushing and River Protection

In this paper, we propose a system of numerical models for the compatibility assessment of reservoir sediment flushing and protection of downstream river environments. The model system is made up of two simulation models. The first model simulates soil erosion in watershed slopes and sediment transport in the tributary of the reservoir by means of a weighted essentially nonoscillatory (WENO) method, which is conservative and fourth-order accurate in space and time. The second model simulates velocity and suspended solid concentration fields in the reservoirs. This model is based on the three-dimensional (3D) numerical integration of motion and concentration equations, expressed in contravariant form on a generalized boundary-conforming curvilinear coordinate system by using a conservative and higher-order accurate numerical scheme. The proposed system of models is applied to the Pieve di Cadore (Veneto, Italy) reservoir and to its catchment area. By comparing suspended solid concentrations that are discha...

Numerical simulation of wave transformation, breaking and runup by a contravariant fully non-linear Boussinesq equations model

In this paper we propose a new model based on a contravariant integral form of the fully non-linear Boussinesq equations (FNBE) in order to simulate wave transformation phenomena, wave breaking, runup and nearshore currents in computational domains representing the complex morphology of real coastal regions. The above-mentioned contravariant integral form, in which Christoffel symbols are absent, is characterized by the fact that the continuity equation does not include any dispersive term. The Boussinesq equation system is numerically solved by a hybrid finite volume-finite difference scheme. A high-order upwind weighted essentially non-oscillatory (WENO) finite volume scheme that involves an exact Riemann solver is implemented. The wave breaking is represented by discontinuities of the weak solution of the integral form of the non-linear shallow water equations (NSWE). On the basis of the shock-capturing high order WENO scheme a new procedure, for the computation of the structure of the solution of a Riemann problem associated with a wet/dry front, is proposed in order to simulate the run up hydrodynamics in swash zone. The capacity of the proposed model to correctly represent wave propagation, wave breaking, run up and wave induced currents is verified against test cases present in literature. The results obtained are compared with experimental measures, analytical solutions or alternative numerical solutions. The proposed model is applied to a real case regarding the simulation of wave fields and nearshore currents in the coastal region opposite San Mauro Cilento (Italy).

Modeling Bed Evolution Using Weakly Coupled Phase-Resolving Wave Model and Wave-Averaged Sediment Transport Model

In this paper, we propose a model for the simulation of the bed evolution dynamics in coastal regions characterized by articulated morphologies. An integral form of the fully nonlinear Boussinesq equations in contravariant formulation, in which Christoffel symbols are absent, is proposed in order to simulate hydrodynamic fields from deep water up to just seaward of the surf zones. Breaking wave propagation in the surf zone is simulated by integrating the nonlinear shallow water equations with a high-order shock-capturing scheme. The near-bed instantaneous flow velocity and the intra-wave hydrodynamic quantities are calculated by the momentum equation integrated over the turbulent boundary layer. The bed evolution dynamics is calculated starting from the contravariant formulation of the advection-diffusion equation for the suspended sediment concentration in which the advective sediment transport terms are formulated according to a quasi-three-dimensional approach, and taking into account the contribution given by the spatial variation of the bed load transport. The model is validated against several tests by comparing numerical results with experimental data. The ability of the proposed model to represent the sediment transport phenomena in a morphologically articulated coastal region is verified by numerically simulating the long-term bed evolution in the coastal region opposite Pescara harbor (in Italy) and comparing numerical results with the field data.

A new three-dimensional finite-volume non-hydrostatic shock-capturing model for free surface flow

In this paper a new finite-volume non-hydrostatic and shock-capturing three-dimensional model for the simulation of wave-structure interaction and hydrodynamic phenomena (wave refraction, diffraction, shoaling and breaking) is proposed. The model is based on an integral formulation of the Navier-Stokes equations which are solved on a time dependent coordinate system: a coordinate transformation maps the varying coordinates in the physical domain to a uniform transformed space. The equations of motion are discretized by means of a finite-volume shock-capturing numerical procedure based on high order WENO reconstructions. The solution procedure for the equations of motion uses a third order accurate Runge-Kutta (SSPRK) fractional-step method and applies a pressure corrector formulation in order to obtain a divergence-free velocity field at each stage. The proposed model is validated against several benchmark test cases.

Bottom changes in coastal areas with complex shorelines

ABSTRACT A model for the sea-bottom change simulations in coastal areas with complex shorelines is proposed. In deep and intermediate water depths, the hydrodynamic quantities are calculated by numerically integrating the contravariant Boussinesq equations, devoid of Christoffel symbols. In the surf zone, the propagation of the breaking waves is simulated by the nonlinear shallow water equations. The momentum equation is solved inside the turbulent boundary layer in order to calculate intra-wave hydrodynamic quantities. An integral formulation for the contravariant suspended sediment advection-diffusion equation is proposed and used for the sea-bottom dynamic simulations. The proposed model is applied to the real case study of Pescara harbor (in Italy).

Contravariant Boussinesq Equations For The Simulation Of Wave Transformation, Breaking And Run-up

We propose an integral form of the fully non-linear Boussinesq equations in contravariant formulation, in which Christoffel symbols are avoided, in order to simulate wave transformation phenomena, wave breaking and near shore currents in computational domains representing the complex morphology of real coastal regions. The motion equations retain the term related to the approximation to the second order of the vertical vorticity. A new Upwind Weighted Essentially Non-Oscillatory scheme for the solution of the fully nonlinear Boussinesq equations on generalised curvilinear coordinate systems is proposed. The equations are rearranged in order to solve them by a high resolution hybrid finite volume–finite difference scheme. The conservative part of the above-mentioned equations, consisting of the convective terms and the terms related to the free surface elevation, is discretised by a high-order shockcapturing finite volume scheme; dispersive terms and the term related to the approximation to the second order of the vertical vorticity are discretised by a cell-centred finite difference scheme. The shock-capturing method makes it possible to intrinsically model the wave breaking, therefore no additional terms are needed to take into account the breaking related energy dissipation in the surf zone. The model is applied on a real case regarding the simulation of wave fields and nearshore currents in the coastal region opposite Pescara harbour (Italy).