Wave-structure interaction generates very complex phenomena involving nonlinear processes, like wave propagation and transformation, run-up, wave breaking, and overtopping. Additionally, complex coastal structures are constructed, with impermeable or porous structures, composed by blocs or arc crown wall structures, etc. Consequently, in practical engineering projects, there are a large number of cases for which there is no appropriated empirical formula. For those cases, physical modeling is currently employed due to the accuracy of this approach and the possibility to model large areas. However, its accurate simulation on physical models strongly depends on the model scale used and needs an understanding of model and scale effects for the correct representation of the phenomenon. For studies of interaction between waves and complex structures as coastal structures, numerical modeling presents a very attractive complement to physical modeling. However, only some numerical models allow simulating wave breaking and wave overtopping correctly. The SPH (Smoothed Particle Hydrodynamics) method is a relatively new method that computes trajectories of fluid particles which interact according to the Navier-Stokes equations. The recent advances on SPH models show that Lagrangian method is a very promising alternative approach to simulate wave-structure interaction due to its completely mesh-free technique. This paper presents an application of a free surface modeling by means of the SPHysics numerical model based on Lagrangian approach. A typical impermeable coastal structure of the Portuguese Atlantic coast is considered in the present study and features of free surface elevation and overtopping are analyzed for two different geometric configurations, differing in the crest level. These two cases represent a range of overtopping conditions varying from small discharges, more difficult to model numerically, to a considerable amount of overtopping.

A lagrangian smoothed particle hydrodynamics - sph - method for modelling waves-coastal structure interaction

This paper describes the set of model scale experiments carried out at the National Civil Engineering Laboratory (LNEC) that aims at simulating, using different model scales, the wave propagation along a constant slope bottom that ends on a sea wall coastal defence structure, a common structure employed in the Portuguese coast. This study focuses especially on the complex physical processes involved in the breaking zone and related to wave-structure interaction (such as wave induced pressures at the structure, run-up levels and wave overtopping). The experiments were performed for different incident wave conditions (regular and irregular) and at several different model scales: 1:10, 1:20, 1:30, 1:40 and 1:60. Measurements of the free surface elevation were made on 26 different locations using wave gauges. Moreover, 30 repetitive tests for a selected wave condition were performed to evaluate the error associated to the signal conversion and its propagation on the calculation of derivative variables. A statistical analysis of the free surface elevation data for the different incident wave conditions for the different model scales with regular and irregular waves is presented. That will permit to evaluate the influence of the geometric scale model and the type of waves (regular or irregular) on the physical model results. Moreover, it was performed a statistical analysis to evaluated the variability of the measurements.

The influence of the geometric scale model on the physical modelling of the wave propagation and breaking in a flume

In the last decade, the numerical methods based on the Lagrangian approach, known generically as SPH models (Smoothed Particle Hydrodynamics), have undertaken a strong development, fostered mainly by the increase in computational capacity. One SPH model that is currently under development is the SPHysics model, which allows modeling free surface flows. SPHysics is a biand tri-dimensional numerical model, based on a Lagrangian method. The model is based on a mesh-free technique and solves the equations of fluid dynamics (Navier-Stokes equations) written in SPH form. This model has been used and developed at the National Civil Engineering Laboratory (LNEC), in order to verify its applicability to studies of wave-structure interaction, specifically for calculating wave overtopping, reflection and forces on structures. This paper presents a brief description of the model and defines values of some model parameters to be used in studies of wave-structure interaction. These values were defined based on the results of previous sensitivity studies and on validation of the model carried out in recent years at LNEC. To illustrate the application of the numerical model SPHysics to study the interaction of waves with impermeable coast protection structures, two case studies are presented for which there are experimental data. These two examples demonstrate the capabilities of SPHysics in modeling complex free surface flows, involving a set of phenomena that significantly change the characteristics of the wave, such as breaking and subsequent reflection on the structure and overtopping. The results of mean overtopping discharge obtained with SPHysics show good agreement with experimental data. For very low overtopping cases, more difficult to model both experimentally and numerically, the initial maximum particle size must be defined carefully in order to obtain results that are not affected by the adopted discretization whilst still keeping the required calculation time to a minimum. Finally, SPHysics is used to model the propagation of regular waves towards a coastal structure with a wave recurve wall. Although experimental data are not available to validate this case, it is relevant to illustrate the potential of the model for the complex phenomena involved, especially the wave interactions with the incident and reflected waves. The presented simulation results show that SPHysics models, without difficulty and with realism, this type of very complex flow that includes the wave surf, the wave action on the recurve wall and the strong interaction between the jet induced by the recurve wall and the wave itself during the run-down. Finally, a summary is presented of the main advantages and limitations of the model when applied to studies of wave-structure interaction. The paper ends with suggestions for future developments of the model in order to make it an efficient and reliable numerical tool for design, optimization and analysis of maritime structures.

/pdf/modelaa-o-da-interaca-o-entre-uma-onda-e-uma-estrutura-de-2osnjsnt5c.pdf

ModelaÁ"o da InteracÁ"o entre uma Onda e uma Estrutura de ProtecÁ"o Costeira usando um Modelo NumÈrico SPH - Smoothed Particles Hydrodynamics * Study of Wave Interaction with Coastal Structures using a SPH Numerical Model

Nesta comunicação, descreve-se o conjunto de ensaios experimentais, realizados em canal para simular a propagação de ondas sobre uma praia de inclinação constante (1:20), que termina numa estrutura de protecção marginal bastante comuns em Portugal Continental. Foram efectuados ensaios com ondas regulares e irregulares, associadas a diferentes alturas de onda e níveis de água, usando diferentes escalas do modelo (1:10 a 1:60). Os resultados obtidos consistiram nas séries temporais da elevação da superfície livre, da pressão sobre a estrutura, do nível de água atingido sobre a estrutura e do volume galgado na mesma, para diferentes condições de agitação incidente. Descrevem-se também as análises de dados realizadas, quer no domínio temporal, quer no domínio da frequência e apresentam-se os resultados obtidos para um caso de estudo, nas três escalas ensaiadas.

Projecto COMIBBS: Modelação Física da Propagação de Ondas em frente a uma Estrutura Costeira

This paper describes the experiments performed at the National Laboratory for Civil Engineering (LNEC) aiming at simulating, in a flume, the wave propagation along a constant slope bottom that ends on a sea wall coastal defence structure, a common structure employed in the Portuguese coast. The objective of these tests is to calibrate the parameters of FUNWAVE, a Boussinesq type model, for wave propagation in coastal regions. This is the first step in the validation of a methodology to combine numerical and physical models in the study of the interactions between beaches and structures. This work is performed in the framework of the Composite Modelling of the Interactions between Beaches and Structures (CoMIBBs) project, a joint research activity of the HYDRALAB III European project.Copyright © 2008 by ASME

A Methodology for the Analysis of Physical Model Scale Effects on the Simulation of Wave Propagation up to Wave Breaking: Preliminary Physical Model Results

Conceic¸a˜o Fortes

Papers

A Methodology for the Analysis of Physical Model Scale Effects on the Simulation of Wave Propagation up to Wave Breaking: Preliminary Physical Model Results