Papers by Giovanni Cannata
Water, Feb 8, 2020
We present a study of wave overtopping of barriers. The phenomenon of the wave overtopping over e... more We present a study of wave overtopping of barriers. The phenomenon of the wave overtopping over emerged structures is reproduced both numerically and experimentally. The numerical simulations are carried out by a numerical scheme for three-dimensional free-surface flows, which is based on the solution of the Navier-Stokes equations in a novel integral form on a time-dependent coordinate system. In the adopted numerical scheme, a novel wet-dry technique, based on the exact solution of the Riemann problem over the dry bed, is proposed. The experimental tests are carried out by adopting a nonintrusive and continuous-in-space image-analysis technique, which is able to properly identify the free surface even in very shallow waters or breaking waves. A comparison between numerical and experimental results, for several wave and water-depth conditions, is shown.
WSEAS transactions on applied and theoretical mechanics, Sep 13, 2022
The three-dimensional motion equations are used to simulate the wave and velocity fields. These e... more The three-dimensional motion equations are used to simulate the wave and velocity fields. These equations are written in integral contravariant form on a time-dependent curvilinear coordinate system. In this paper a new − turbulence model in contravariant form is proposed for three-dimensional simulation of breaking waves. In this model the mixing length is defined as a function of the first and second spatial derivatives of the maximum water surface elevation.
WSEAS transactions on fluid mechanics, Jul 18, 2022
We present a new three-dimensional numerical model for the simulation of breaking waves. In the p... more We present a new three-dimensional numerical model for the simulation of breaking waves. In the proposed model, the integral contravariant form of the Navier-Stokes equations is expressed in a curvilinear moving coordinate system and are integrated by a predictor-corrector method. In the predictor step of the method, the equations of motion are discretized by a shock-capturing scheme that is based on an original highorder scheme for the reconstruction of the point values of the conserved variables on the faces of the computational grid. On the cell faces, the updating of the point values of the conserved variables is carried out by an exact Riemann solver. The final flow velocity field is obtained by a corrector step which is based exclusively on conserved variables, without the need of calculating an intermediate field of primitive variables. The new three-dimensional model significantly reduces the kinetic energy numerical dissipation introduced by the scheme. The proposed model is validated against experimental tests of breaking waves and is applied to the three-dimensional simulation of the local vortices produced by the interaction between the wave motion and an emerged barrier.
A numerical and experimental analysis of the wave overtopping over emerged and submerged structur... more A numerical and experimental analysis of the wave overtopping over emerged and submerged structures, is presented. An original model is used in order to simulate three-dimensional free surface flows. The model is based on the numerical solution of the motion equations expressed in an integral form in timedependent curvilinear coordinates. A non-intrusive and continuous-in-space image analysis technique, which is able to properly identify the free surface even in very shallow waters or breaking waves, is adopted for the experimental tests. Numerical and experimental results are compared, for several wave and water depth conditions.
Journal of Marine Science and Engineering, Mar 28, 2023
Journal of Marine Science and Engineering
The simulation of the propagation and evolution of sea waves in coastal regions and their interac... more The simulation of the propagation and evolution of sea waves in coastal regions and their interaction with coastal structures is a very useful engineering tool in several problems of coastal and environmental engineering [...]
Water
In this paper, the hydrodynamic and free surface elevation fields in breaking waves are simulated... more In this paper, the hydrodynamic and free surface elevation fields in breaking waves are simulated by solving the integral and contravariant forms of the three-dimensional Navier–Stokes equations that are expressed in a generalized time-dependent curvilinear coordinate system, in which the vertical coordinate moves by following the free surface. A new k−l turbulence model in contravariant form is proposed; in this model, the mixing length, l, is defined as a function of the maximum water surface elevation variation. A new original numerical scheme is proposed. The main element of originality of the numerical scheme consists of the proposal of a new fifth-order reconstruction technique for the point values of the conserved variables on the cell face. This technique, named in the paper as WTENO, allows the choice procedure of the reconstruction polynomials for the point values to be modified in a dynamic way.
XXXIII Convegno Nazionale di Idraulica e Costruzioni Idrauliche, 2012
Journal of Marine Science and Engineering
A new three-dimensional high-order shock-capturing model for the numerical simulation of breaking... more A new three-dimensional high-order shock-capturing model for the numerical simulation of breaking waves is proposed. The proposed model is based on an integral contravariant form of the Navier–Stokes equations in a time-dependent generalized curvilinear coordinate system. Such an integral contravariant form of the equations of motion is numerically integrated by a new conservative numerical scheme that is based on three elements of originality: the time evolution of the state of the system is carried out using a predictor–corrector method in which exclusively the conserved variables are used; the point values of the conserved variables on the cell face of the computational grid are obtained using an original high-order reconstruction procedure called a wave-targeted essentially non-oscillatory scheme; the time evolution of the discontinuity on the cell faces is calculated using an exact Riemann solver. The proposed model is validated by numerically reproducing several experimental t...
This numerical study investigated the effects of a vegetation patch on the flow of a channel. The... more This numerical study investigated the effects of a vegetation patch on the flow of a channel. The numerical approach consisted of a CFD, 3-D model that applied the RANS equations to simulate the flow field, and the VOF model to represent the free surface. The patch altered the initial flow by inducing regions of reduced velocity in the patch wake (approximately 40% reduction), and regions of enhanced velocity around of the patch (approximately 16% increase), and these regions extended throughout the water depth. Also, the patch induced a small change of 3.83% in the water surface, in the streamwise direction.
Proceedings of the International Conference on Fluvial Hydraulics, Lisbon, Portugal, 6-8 September 2006, 2006
Computational Methods in Multiphase Flow IV, 2007
A new model of LES is proposed together with a new methodology for the simulation of concentratio... more A new model of LES is proposed together with a new methodology for the simulation of concentration fields of contaminant coherent with the LES methodology. In this paper a new LES model is proposed. The closure relation for the generalised SGS turbulent stress tensor: a) complies with the principle of turbulent frame indifference; b) takes into account both the anisotropy of the turbulence velocity scales and turbulence length scales; c) removes any balance assumption between the production and dissipation of SGS turbulent kinetic energy. In the proposed model: a) the closure coefficient which appears in the closure relation for the generalised SGS turbulent stress tensor is theoretically and uniquely determined without adopting Germano's dynamic procedure; b) the generalised SGS turbulent stress tensor is related exclusively to the generalised SGS turbulent kinetic energy (which is calculated by means of its balance equation) and the modified Leonard tensor. The calculation of the viscous dissipation is carried out by integrating its exact balance equation. In this paper the form invariance and frame dependence of the above mentioned equation of the viscous dissipation transport is shown. The concentration field is simulated by the spatially filtered equation of the concentration. In this equation the first-order tensor (produced by the correlation between the velocity and the concentration) is related to the gradient of the resolved concentration according to an original dynamic Germano procedure.
Journal of Hydraulic Engineering, 2011
ABSTRACT In this paper, we propose a system of numerical models for the compatibility assessment ... more ABSTRACT 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 discharged through the bottom outlets during flushing operations with suspended solid concentrations in the main river during natural flooding, we perform an assessment of the compatibility between sediment flushing and the protection of the river ecosystem downstream
International Journal for Numerical Methods in Fluids, 2010
Page 1. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS Int. J. Numer. Meth. Fluids (2010) ... more Page 1. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS Int. J. Numer. Meth. Fluids (2010) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/fld.2392 Central WENO scheme ...
Continuum Mechanics and Thermodynamics, 2005
In this paper we demonstrate that the transport equation of the generalised subgrid scale (SGS) t... more In this paper we demonstrate that the transport equation of the generalised subgrid scale (SGS) turbulent stress tensor is form-invariant but not frame-indifferent under Euclidean transformations of the frame. A new closure equation between the generalized SGS turbulent stress tensor and the resolved kinematic quantities is proposed. The closure equation at the basis of the proposed model (Two-Equation Model, TEM): a) respects the principle of the turbulence frame indifference [1]; b) takes into account both the anisotropy of the turbulence velocity scales and turbulence length scales; c) removes any balance assumption between the production and dissipation of SGS turbulent kinetic energy; d) assumes scale similarity in the definition of the second-order tensor representing the turbulent velocity scales. In the proposed model: a) the closure coefficient C which appears in the constitutive equation is uniquely determined without using Germano's dynamic procedure [2]; b) the generalized SGS turbulent stress tensor is related exclusively to the generalized SGS turbulent kinetic energy (which is calculated by means of its balance equation) and the modified Leonard tensor; c) the viscous dissipation ε of the generalized SGS turbulent kinetic energy is calculated by solving the ε balance equation. The proposed model is tested for a turbulent channel flow at Reynolds numbers (based on friction velocity and channel half-width) ranging from 180 to 2340.
Computers & Fluids, 2012
An Upwind Weighted Essentially Non-Oscillatory scheme for the solution of the Shallow Water Equat... more An Upwind Weighted Essentially Non-Oscillatory scheme for the solution of the Shallow Water Equations on generalized curvilinear coordinate systems is proposed. The Shallow Water Equations are expressed in a contravariant formulation in which Christoffel symbols are avoided. The equations are solved by using a high-resolution finite-volume method incorporated with an exact Riemann solver. A procedure developed in order to correct errors related to the difficulties of numerically satisfying the metric identities on generalized boundary-conforming grids is presented; this procedure allows the numerical scheme to satisfy the freestream preservation property on highly-distorted grids. The proposed scheme ensures the satisfaction of the C-property. The model is verified against several benchmark tests, and the results are compared with theoretical and alternative numerical solutions.
Coastal Engineering, 2014
In this paper we propose an integral form of the fully non-linear Boussinesq equations in contrav... more In this paper 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 nearshore currents in computational domains representing the complex morphology of real coastal regions. Following the approach proposed by Chen (2006), 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 non-linear 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 in which an exact Riemann solver is involved; 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 verified against several benchmark tests, and the results are compared with experimental, theoretical and alternative numerical solutions.
Proceedings of the Sixth International Symposium On Turbulence, Heat and Mass Transfer, 2009
In this paper the relation between the Noll formulation of the Principle of Material Frame-Indiff... more In this paper the relation between the Noll formulation of the Principle of Material Frame-Indifference and the Hutter & Joehnk formulation of the Principle of Turbulent Frame-Indifference in Large Eddy Simulation is revised; the definition of a new rule for the formulation of turbulent closure relations is proposed. In this paper we demonstrate the Euclidean form-invariance and frame-dependence of the transport equation of the generalised SGS viscous dissipation ε . New closure relations for the SGS viscous dissipation transport equation are proposed. The proposed closure relations allow the modeled balance equation of ε to respect the properties of Euclidean form-invariance and frame-dependence of the exact equation
Water Resources Management V, 2009
Reservoirs (which are created by the artificial barrage of watercourses) gradually lose the capac... more Reservoirs (which are created by the artificial barrage of watercourses) gradually lose the capacity to store water resources owing to the progressive accumulation of solid particles, which are transported by the watercourses, on the bed. In conditions characterized by a flood with a high capacity for transporting large quantities of solid material, turbidity currents could occur; in these situations and in the presence of a steep bed slope, the turbidity currents can reach the bottom outlets. In this paper a model for the simulation of the turbidity currents is proposed; the model is based on the numerical integration of the two phase flow motion equations. These equations are integrated on a three-dimensional generalised curvilinear grid and are directly expressed in contravariant formulation. The numerical procedure adopted is based on a fractional step method and the proposed numerical scheme is conservative and fourth order accurate. The numerical model is validated by comparison between the numerical results and experimental data and is applied to the reservoir of Pieve di Cadore (Italy), in order to verify the possibility of the production of turbidity currents and the possibility of using the bottom outlet to discharge downstream the solid material that reaches the reservoir during flood events.
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Papers by Giovanni Cannata