1,720,961 research outputs found
Two-dimensional and three-dimensional non hydrostatic models for fully non-linear and dispersive hydrodynamic processes
Full text linkThe thesis is divided in two main parts. In the first part is presented a model based on a numerical integration of a new conservative form of the Fully Non-linear Boussinesq Equations (FNBE) in a contravariant formulation. As known coastal regions are characterized by a very complex morphology: presence of anthropic structures, river mouth or shoreline with articulated geometry. The use of orthogonal grid, as Cartesian coordinate, requests a huge number of calculus points that may be prohibitive. To solve this issue, a well known strategy is to integrate the motion equations on generalized curvilinear boundary conforming grid.
In the second part it is presented an original fully non-hydrostatic three-dimensional model based on the numerical integration of Navier-Stokes Equations in time dependent coordinate system. The use of time dependent coordinate system allows to assign, without any approximations, bottom and free surface kinematic conditions and zero pressure condition at the upper boundary of the domain. Unlike the depth averaged model, this model is able to simulate the three-dimensionality of hydrodynamic phenomena related to the wave motion of unsteady flows.
The proposed model belongs to the group of the so-called “free surface fully non-hydrostatic three-dimensional models”. These models are often used to analyze local phenomena, to evaluate flow-structure interaction, for sediment transport analysis and to study turbulences phenomena related with them. In general the free surface fully non-hydrostatic three-dimensional models are used for all engineering problems for which is necessary to know the vertical distribution of hydrodynamic quantities
Numerical simulation of wave transformation, breaking and runup by a contravariant fully non-linear Boussinesq equations model
No full textIn 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)
Non-Linear Shallow Water Equations numerical integration on curvilinear boundary-conforming grids
Full text linkAn 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 capacity of the proposed model is verified against test cases present in literature. The results obtained are compared with analytical solutions and alternative numerical solutions
A contravariant formulation of Non-linear Shallow Water Equations
No full textAn 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 numerical model for the simulation of a solitary wave in a coastal region
Full text linkIn this paper we propose a numerical model for the simulation of the tsunami wave propagation on coastal region. The model can simulate the wave transformation due to refraction, shoaling, diffraction and breaking phenomena that take place in the surf zone and can simulate the wet front progress on the mainland. The above mentioned model is based on the numerical integration of the Fully Non-linear Boussinesq Equations in the deep water region and of the Non-linear Shallow Water Equations in the surf zone. These equations are expressed in an integral contravariant formulation and are integrated on generalized curvilinear boundary conforming grid that can reproduce the complex morphology of the coast line. The numerical integration of the model equations is implemented by a high order Upwind WENO numerical scheme that involves an exact Riemann Solver. For the simulation of the wet front progress on the dry bed, the exact solution of the Riemann problem for the wet-dry front is used. The capacity of the proposed model to simulate the wet front progress velocity is tested by numerical reproducing the dam-break problem on a dry bed. The capacity of the proposed model to correctly simulate the tsunami wave evolution and propagation on the coastal region is tested by numerical reproducing a benchmark test case about the tsunami wave propagation on a conic island
A new numerical model for simulations of wave transformation, breaking and long-shore currents in complex coastal regions
No full textIn this paper, we propose a model based on a new contravariant integral form of the fully nonl inearBoussinesq equations in order to simulate wave transformation phenomena, wave breaking, and nearshorecurrents in computational domains representing the complex morphology of real coastal regions. The afore-mentioned contravariant integral form, in which Christoffel symbols are absent, is characterized by the factthat the con tinuity equation does not include any dispersive term. A procedure developed in order to correcterrors related to the difficult ies of numerically satisfying the metric identities in the numerical integration offully nonlinear Bous sinesq equation on generalized boundary-conforming grids is presented. TheBoussinesq equation system is numerically solved by a hybrid finite volume–finite difference scheme.The proposed high-order upwind weighted essentially non-oscillatory finite volume scheme involves anexact Riemann solver and is based on a genuinely two-dimensional reconstruction procedu re, which usesa convex combination of biquadratic polynomials. The wave breaking is represented by discontinuities ofthe weak solution of the integral form of the nonlin ear shallow water equations.The capacity of the proposed model to correctly represent wave propagation, wave breaking, and wave-induced currents is verified against test cases present in the literature. The results obtained are comparedwith experimental measures, analytical solutions, or alternative numerical solutions
A new three-dimensional finite-volume non-hydrostatic shock-capturing model for free surface flow
No full textIn 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
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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