Reflection effects on wave field within a harbour

1993 ◽  
Vol 20 (3) ◽  
pp. 386-397 ◽  
Author(s):  
Michael Isaacson ◽  
Enda O'Sullivan ◽  
John Baldwin
Keyword(s):  
Numerical Model ◽  
Wave Field ◽  
Wave Reflection ◽  
Diffraction Theory ◽  
Specific Reference ◽  
Wave Source ◽  
Numerical Predictions ◽  
Diffraction Wave ◽  
Reflecting Boundaries ◽  
Reflection Boundary

The present paper outlines a numerical model for predicting the wave field in a harbour with partially reflecting boundaries, and describes laboratory tests undertaken to assess the model. The numerical model is based on linear diffraction theory and involves the application of a partial reflection boundary condition. By utilizing a wave doublet representation of the fluid boundaries instead of the usual wave source representation, the extension is made to general harbour configurations that include breakwaters. Numerical results are compared with known solutions for specific reference configurations. Laboratory measurements have been made of the wave field within a particular harbour model having portions of the boundary corresponding to different degrees of wave reflection. A comparison with the numerical predictions is summarized and highlights the importance of adequately modelling the partial reflections within the harbour. Key words: breakwaters, coastal engineering, harbours, waves, wave diffraction, wave reflection.

Predicted wave field in a laboratory wave basin

1990 ◽  
Vol 17 (6) ◽  
pp. 1005-1014 ◽  
Author(s):  
Michael Isaacson ◽  
Shiqin Qu
Keyword(s):  
Wave Field ◽  
Wave Diffraction ◽  
Diffraction Theory ◽  
Ocean Engineering ◽  
Laboratory Facilities ◽  
Rectangular Basin ◽  
Diffraction Wave ◽  
Wave Basin ◽  
Wave Generator ◽  
Reflection Boundary

The present paper describes a numerical method for predicting the wave field produced by a segmented wave generator undergoing specified motions in a wave basin which may contain partially reflecting sides. The approach used is based on linear diffraction theory and utilizes a point source representation of the generator segments and any reflecting walls that are present. The method involves the application of a partial reflection boundary condition, which is discussed. Numerical results are presented for the propagating wave field due to specified wave generator motions in a rectangular basin. Cases that are considered include both perfectly absorbing and partially reflecting beaches along the basin sides, as well as the presence of perfectly reflecting short sidewalls near the generator. The method appears able to account adequately for the effects of wave diffraction and partial reflections, and to predict the generated wave field realistically. Key words: coastal engineering, hydrodynamics, laboratory facilities, ocean engineering, wave diffraction, wave generation, wave reflection.

Wave reflection effects on small craft motions

1996 ◽  
Vol 23 (2) ◽  
pp. 340-346
Author(s):  
Michael Isaacson ◽  
John Baldwin ◽  
Andrew Kennedy
Keyword(s):  
Numerical Model ◽  
Wave Reflection ◽  
Numerical Study ◽  
Diffraction Theory ◽  
Coastal Engineering ◽  
Irregular Waves ◽  
Induced Response ◽  
Small Craft ◽  
Wave Heights ◽  
Wave Induced

This paper describes an experimental and a numerical study of the wave-induced response of a moored vessel near a reflecting wall, for the purpose of incorporating wave reflection effects into wave agitation criteria for small craft harbours. The motions of a model vessel have been measured for a range of wave heights, wave periods, wave directions, mooring conditions, and vessel locations, and with both regular and irregular waves. These have been compared with the results of a numerical model based on linear diffraction theory. An expression is developed to relate vessel motions near a partially reflecting wall to motions in unreflected waves. This has been found to agree well with the experimental results, and is used to recommend an extension to existing wave agitation criteria for small craft harbours so as to take account of the presence of reflecting walls. Key words: coastal engineering, harbours, hydrodynamics, marinas, wave agitation, waves.

Comparison of Four Friction Models: Feature Prediction

2015 ◽  
Vol 11 (3) ◽  
Author(s):  
Yun-Hsiang Sun ◽  
Tao Chen ◽  
Christine Qiong Wu ◽  
Cyrus Shafai
Keyword(s):  
Numerical Model ◽  
Viscous Friction ◽  
Friction Model ◽  
Dynamic Features ◽  
Numerical Predictions ◽  
Wide Range ◽  
Model Predictions ◽  
Friction Models ◽  
Parameter Identifications ◽  
Model Structures

In this paper, we provide not only key knowledge for friction model selection among candidate models but also experimental friction features compared with numerical predictions reproduced by the candidate models. A motor-driven one-dimensional sliding block has been designed and fabricated in our lab to carry out a wide range of control tasks for the friction feature demonstrations and the parameter identifications of the candidate models. Besides the well-known static features such as break-away force and viscous friction, our setup experimentally demonstrates subtle dynamic features that characterize the physical behavior. The candidate models coupled with correct parameters experimentally obtained from our setup are taken to simulate the features of interest. The first part of this work briefly introduces the candidate friction models, the friction features of interest, and our experimental approach. The second part of this work is dedicated to the comparisons between the experimental features and the numerical model predictions. The discrepancies between the experimental features and the numerical model predictions help researchers to judge the accuracy of the models. The relation between the candidate model structures and their numerical friction feature predictions is investigated and discussed. A table that summarizes how to select the most optimal friction model among a variety of engineering applications is presented at the end of this paper. Such comprehensive comparisons have not been reported in previous literature.

scholarly journals NUMERICAL PREDICTIONS AND MECHANICAL TESTING OF BRAIDED COMPOSITE STRUCTURES UTILISING DIGITAL IMAGE CORRELATION

2016 ◽  
Vol 7 ◽  
pp. 43
Author(s):  
Emil Pitz ◽  
Matei-Constantin Miron ◽  
Imre Kállai ◽  
Zoltán Major
Keyword(s):  
Numerical Model ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Composite Structures ◽  
Experimental Testing ◽  
Single Layer ◽  
Failure Criteria ◽  
Image Correlation ◽  
Braided Composites ◽  
Numerical Predictions

The current paper is describing the implementation of a multiscale numerical model for prediction of stiffness and strength in braided composites. The model is validated by experimental testing of single-layer braided tubes under torsional loading utilising digital image correlation (DIC). For the numerical model the entire braided structure is modelled at yarn detail level, taking into account the yarn behaviour as well as individual yarn-to-yarn interactions by using cohesive contact definitions. By means of Hashin’s failure criteria and cohesive contact damage, failure of the yarns and failure of the yarn-to-yarn interface is being accounted for. Thereby the material failure behaviour can be predicted. For validation of the model, torsion tests of biaxially braided single-layer composite tubes were performed. The strain distribution at the specimen surface was studied using the DIC system ARAMIS in 3D mode.

Experimental and Numerical Study of Ballistic Impact Performance on UHMWPE Composites

2013 ◽  
Vol 818 ◽  
pp. 30-36 ◽  
Author(s):  
Yao Ke Wen ◽  
Cheng Xu ◽  
Ai Jun Chen ◽  
Shu Wang
Keyword(s):  
Numerical Model ◽  
Composite Plate ◽  
Numerical Study ◽  
Von Mises Stress ◽  
High Speed Photography ◽  
Numerical Predictions ◽  
Back Face ◽  
Uhmwpe Composites ◽  
The Impact ◽  
Bulge Height

A series of ballistic tests were performed to investigate the bulletproof performance of UHMWPE composites. The temporal evolution of the UHMWPE composite plate back-face bulge height and diameter were captured by high-speed photography. The experiments show the composite plate were perforated when the impact velocity greater than 880m/s. The maximum bulge height and diameter can reach to 3.63-8.23mm and 37-64.5mm at the experimental velocity range , respectively. After that, the numerical model was built with composite material model MAT59 in LS-DYNA and stress based contact failure between plies were adopted to model the delamination mechanism. The number of plies of numerical model shows a strong dependency on the numerical results. Comparisons between numerical predictions and experimental results in terms of bulge height and diameter are presented and discussed. The maximum bulge diameter is good agreement with experiment, but the computational results under predict the maximum bulge height. The computational analysis show the damage development of the plate penetration by the projectile is shearing dominated at first, then the plate undergoes delamination and stretching in the later part of the impact process. The von mises stress at front and back face of the plate were also studied.

Numerical Simulation of Wave Interaction With a Pair of Fixed Large Tandem Cylinders Subjected to Regular, Non-Breaking Waves

2021 ◽  
Author(s):  
M. Mohseni ◽  
C. Guedes Soares
Keyword(s):  
Numerical Model ◽  
Wave Field ◽  
Circular Cross Section ◽  
Wave Interaction ◽  
Breaking Waves ◽  
Wave Loading ◽  
Two Phase ◽  
Wave Regime ◽  
Wave Amplification ◽  
Vof Model

Abstract The wave interaction with cylinders placed in proximity results in significant modification of the wave field, wave-induced processes, and wave loading. The evaluation of such a complex wave regime and accurate assessment of the wave loading requires an efficient and accurate numerical model. Concerning the wave scattering types identified by Swan et al. (2015) and lateral progressive edge waves, this paper presents the application of a two-phase Computational Fluid Dynamics (CFD) model to carry out a detailed investigation of nonlinear wave field surrounding a pair of columns placed in the tandem arrangement in the direction of wave propagation and corresponding harmonics. The numerical analysis is conducted using the Unsteady Reynolds-Averaged Navier-Stokes/VOF model based on the OpenFOAM framework combined with the olaFlow toolbox for wave generation/absorption. For the simulations, the truncated cylinders are assumed vertical and surface piercing with a circular cross-section subjected to regular, non-breaking fifth-order Stokes waves propagating with moderate steepness in deep water. Primarily, the numerical model is validated with experimental data provided by ITTC (OEC)[1] for a single cylinder. Future, the given simulations are conducted for different centre-to-centre distances between the tandem large cylinders. The results show the evolution of a strong wave diffraction pattern and consequently high wave amplification harmonics around cylinders are apparent.

scholarly journals Wave field reconstruction and phase imaging by electron diffractive imaging

Microscopy ◽  
2020 ◽  
Author(s):  
Jun Yamasaki
Keyword(s):  
Wave Field ◽  
Real Space ◽  
Phase Image ◽  
Phase Imaging ◽  
Diffractive Imaging ◽  
Diffraction Wave ◽  
Phase Images ◽  
Applicable Range ◽  
The Fourier Transform

Abstract In electron diffractive imaging, the phase image of a sample is reconstructed from its diffraction intensity through iterative calculations. The principle of this method is based on the Fourier transform relation between the real-space wave field transmitted by the sample and its Fraunhofer diffraction wave field. Since Gerchberg’s experimental work in 1972, various advancements have been achieved, which have substantially improved the quality of the reconstructed phase images and extended the applicable range of the method. In this review article, the principle of diffractive imaging, various experimental processes using electron beams and application to specific samples are explained in detail.

scholarly journals Development of An Integrated Numerical Model for Simulating Wave Interaction with Permeable Submerged Breakwaters Using Extended Navier–Stokes Equations

2020 ◽  
Vol 8 (2) ◽  
pp. 87 ◽  
Author(s):  
Paran Pourteimouri ◽  
Kourosh Hejazi
Keyword(s):  
Porous Medium ◽  
Wave Propagation ◽  
Numerical Model ◽  
Analytical Solutions ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Stokes Wave ◽  
Navier Stokes Equations ◽  
Numerical Predictions ◽  
The Impact

An integrated two-dimensional vertical (2DV) model was developed to investigate wave interactions with permeable submerged breakwaters. The integrated model is capable of predicting the flow field in both surface water and porous media on the basis of the extended volume-averaged Reynolds-averaged Navier–Stokes equations (VARANS). The impact of porous medium was considered by the inclusion of the additional terms of drag and inertia forces into conventional Navier–Stokes equations. Finite volume method (FVM) in an arbitrary Lagrangian–Eulerian (ALE) formulation was adopted for discretization of the governing equations. Projection method was utilized to solve the unsteady incompressible extended Navier–Stokes equations. The time-dependent volume and surface porosities were calculated at each time step using the fraction of a grid open to water and the total porosity of porous medium. The numerical model was first verified against analytical solutions of small amplitude progressive Stokes wave and solitary wave propagation in the absence of a bottom-mounted barrier. Comparisons showed pleasing agreements between the numerical predictions and analytical solutions. The model was then further validated by comparing the numerical model results with the experimental measurements of wave propagation over a permeable submerged breakwater reported in the literature. Good agreements were obtained for the free surface elevations at various spatial and temporal scales, velocity fields around and inside the obstacle, as well as the velocity profiles.

3D Numerical Simulation and PEPT Experimental Investigation of Pressurized Gas-Solid Fluidized Bed Hydrodynamic

2009 ◽  
Author(s):  
P. Fede ◽  
G. Moula ◽  
A. Ingram ◽  
T. Dumas ◽  
O. Simonin
Keyword(s):  
Numerical Model ◽  
Fluidized Bed ◽  
Particle Velocity ◽  
Particle Trajectory ◽  
Wall Region ◽  
3 Dimensional ◽  
The Core ◽  
Numerical Predictions ◽  
Model Predictions ◽  
Good Agreement

The present paper is dedicated to numerical and experimental study of the hydrodynamic of a non-reactive isothermal pressurized fluidized bed. Experimental data have been obtained using PEPT technique allowing to track a particle trajectory inside a dense fluidized bed. A specific post-processing approach has been developed to compute the Eulerian time-averaged particle velocity field. The comparison with 3-dimensional numerical model predictions shows a good agreement in the core of the fluidized bed. In contrast, in the near wall region the numerical model overestimate the downward particle velocity. The modification of particle phase wall boundary condition improves the numerical predictions.

Comparison of Mooring Loads in Survivability Mode on the Wave Dragon Wave Energy Converter Obtained by a Numerical Model and Experimental Data

2012 ◽  
Author(s):  
Stefano Parmeggiani ◽  
Made Jaya Muliawan ◽  
Zhen Gao ◽  
Torgeir Moan ◽  
Erik Friis-Madsen
Keyword(s):  
Numerical Model ◽  
Wave Energy ◽  
Complex Geometry ◽  
Wave Energy Converter ◽  
Scale Model ◽  
Coupled Analysis ◽  
Small Scale ◽  
Energy Converter ◽  
Numerical Predictions ◽  
Small Scale Model

The Wave Dragon Wave Energy Converter is ready to be up-scaled to commercial size. The design and feasibility analysis of a 1.5 MW pre-commercial unit to be deployed at the DanWEC test center in Hanstholm, Denmark, is currently ongoing. With regard to the mooring system, the design has to be carried out numerically, through coupled analyses of alternative solutions. The present study deals with the preliminary hydrodynamic characterization of Wave Dragon needed in order to calibrate the numerical model to be used for the mooring design. A hydrodynamic analysis of the small scale model in the frequency domain is performed by the software HydroD, which uses WAMIT as core software. The quadratic damping term, accounting for the viscous effect, is determined through an iterative procedure aimed at matching numerical predictions on the mooring tension, derived through time domain coupled analysis, with experimental results derived from tank tests of a small scale model. Due to the complex geometry of the device, a sensitivity analysis is performed to discuss the influence of the mean position on the quality of the numerical predictions. Good correspondence is achieved between the experimental and numerical model. The numerical model is hence considered reliable for future design applications.

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