1,720,967 research outputs found
Numerical modelling of wave fields and currents in coastal area
Full text linkThe design and management of coastal engineering, like harbors and coastal defense structures, requires the simulation of hydrodynamic phenomena. This special issue collects five original papers that address state of the art numerical simulations of wave fields and wave-induced velocity fields in coastal areas. The first paper proposes a turbulence model for wave breaking simulation, which is expressed in terms of turbulent kinetic energy and dissipation rate of turbulent kinetic energy (k-e); the proposed turbulence model is a modification of the standard k-e turbulence models. The second paper investigates modalities by which wind interacts with wave motion, modifying the wave propagation dynamic. The third paper proposes a study on waves overtopping over coastal barriers. The fourth paper details the numerical simulation of a tsunami wave that propagates over an artificial reservoir, caused by a landslide that creates a solid mass to detach from the slopes and to slide into the reservoir. The fifth paper examines an application case concerning Cetraro harbor (Italy), which is carried out using three-dimensional numerical simulations of wave motion
Hydrodynamic effects produced by submerged breakwaters in a coastal area with a curvilinear shoreline
Full text linkA three-dimensional numerical study of the hydrodynamic effect produced by a system of submerged breakwaters in a coastal area with a curvilinear shoreline is proposed. The three-dimensional model is based on an integral contravariant formulation of the Navier-Stokes equations in a time-dependent curvilinear coordinate system. The integral form of the contravariant Navier-Stokes equations is numerically integrated by a finite-volume shock-capturing scheme which uses Monotonic Upwind Scheme for Conservation Laws Total Variation Diminishing (MUSCL-TVD) reconstructions and an Harten Lax van Leer Riemann solver (HLL Riemann solver). The numerical model is used to verify whether the presence of a submerged coastal defence structure, in the coastal area with a curvilinear shoreline, is able to modify the wave induced circulation pattern and the hydrodynamic conditions from erosive to accretive
Simulazione numerica tridimensionale dei campi di moto indotti dal vento
No full textNell’articolo viene proposto un modello numerico tridimensionale al volume finiti, che viene utilizzato per la simulazione di campi di moto indotti dal mento in corpi idrici con batimetria complessa. I risultati numerici sono confrontati con misure sperimentali. Al fine di verificare gli effetti sul calcolo del campi idrodinamici di alcume ipotesi simplificative, relative alla distribuzione verticale della pressione e degli sforzi di Reynolds, sono stati quindi condotti alcuni test numerici, dai quali si è evidenziato che l’ipotesi di distribuzione idrostatica delle pressioni, cui si fa ricorso nelle approssinazioni di tipo “quasi-3D”, può essere utilizzata per il carcolo del profili verticali della componente di clocità orizaontale ad una certa distanza dalle pereti, ma conduce a risultati poco corrtti in prossimità delle pareti di monte e di valle. Si è inotre verificata l’applicabilità del modello algbrico proposto da Tsanis [23], confrontando il profilo parabolico del coefficiente di viscosità tubolenta assunto da questo mmodello con quello resultante dall’utilizzo del modello K. Tali profili risultano in buon accordo nella maggior parte del dominio considerato, sebbene il modello di Tsanis sobrastimi decisamente le viscosità turbolente in prossimità delle pareti di monte e di valle
Effects of aerodynamic appendices on the flutter characteristics of long-span bridge decks
No full textThis research deals with the effects produced by aerodynamic appendices on the aeroelastic stability of long-span bridge decks. A simulation model is presented by which the structural motion and the fluid flow are together and simultaneously simulated. The deck is schematised as a bidimensional two-degree-of-freedom rigid oscillator, whilst the aerodynamic fields are simulated by numerically solving the 2D Arbitrary Lagrangian-Eulerian (ALE) formulated Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations on moving meshes which adjust to the deck motion. The proposed finite volume method is based on high order Weighted Essentially Non-Oscillatory (WENO) reconstructions. The time discretisation is performed by a five stage fourth order accurate Strong Stability Preserving Runge-Kutta (SSPRK) method. It is shown that the proposed numerical method makes it possible to ensure both high accuracy in time and space. The simulation model is validated by comparing the numerical results with experimental data and is applied to the evaluation of the aeroelastic stability of the forth road suspension bridge deck. The effects of aerodynamic appendices on the flutter characteristics of the forth road bridge are investigated via the proposed simulation model. It is demonstrated that the presence of the cross-section details (barriers, railings, dividing strips) makes the aeroelastic stability of the deck worse and that the flutter sensitivity is mitigated by introducing a couple of sloping barriers at the edges of the deck
Numerical integration of the contravariant form of the two phase flow motion equations
No full textReservoirs (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
Numerical Simulation of the Shoreline Modifications behind a T-Head Groin
Full text linkIn this paper, the shoreline and bottom modifications produced by the presence of a T-head groin are simulated. We present a model for the bottom-change simulation, composed by two sub-models: a two-dimensional phase-resolving model for the simulation of the variation of the fluid dynamic variables inside the wave period and that takes into account the undertow; a second morphodynamic sub-model for the simulation of the bottom changes, in which the suspended sediment concentration is calculated by means of the wave-averaged advection-diffusion equation. Both the fluid motion equation and the concentration equation are written in a new contravariant formulation. We simulate the velocity fields from deep water to the start of the surf-zone by a new integral contravariant form of the Fully Nonlinear Boussinesq Equations. We simulate the bed evolution dynamics by means of the contravariant formulation of the advection-diffusion equation for the suspended sediment concentration. A quasi three-dimensional approach is used to formulate the advective sediment transport terms in the advection-diffusion equation
A new turbulence model for breaking wave simulations
Full text linkIn 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 fifthorder 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
A Modified k – ε Turbulence Model for aWave Breaking Simulation
Full text linkWe propose a two-equation turbulence model based on modification of the k−ε standard model, for simulation of a breaking wave. The proposed model is able to adequately simulate the energy dissipation due to the wave breaking and does not require any “a priori” criterion to locate the initial wave breaking point and the region in which the turbulence model has to be activated. In order to numerically simulate the wave propagation from deep water to the shoreline and the wave breaking, we use a model in which vector and tensor quantities are expressed in terms of Cartesian components, where only the vertical coordinate is expressed as a function of a time-dependent curvilinear coordinate that follows the free surface movements. A laboratory test is numerically reproduced with the aim of validating the turbulence modified k−ε model. The numerical results compared with the experimental measurements show that the proposed turbulence model is capable of correctly estimating the energy dissipation induced by the wave breaking, in order to avoid any underestimation of the wave heigh
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