Generation of Harmonics by Non-Breaking Water Waves Over Permeable Submerged Breakwaters

2004 ◽  
Vol 20 (1) ◽  
pp. 57-67
Author(s):  
Chao-Lung Ting ◽  
Ming-Chung Lin
Keyword(s):  
Experimental Data ◽  
Harmonic Generation ◽  
Water Waves ◽  
Breaking Waves ◽  
Interesting Phenomenon ◽  
Frequency Components ◽  
Wave Profiles ◽  
Generation Of Harmonics ◽  
Submerged Obstacles ◽  
Submergence Depth

ABSTRACTThis work examines the interesting phenomenon of the generation of harmonics by non-breaking waves over permeable submerged obstacles. Nine model geometries, each with six different porosities, from 0.421 to 0.912, were considered to examine the effects of model width, porosity, and submergence depth on harmonic generation. The results revealed coupled effects on harmonic generation. A modified Ursell number was proposed to analyze experimental data. Almost no harmonic generation occurs at a modified Ursell number of less than five and/or a model width to wavelength ratio of over 1.6. After harmonics have been generated, wave profiles become dimpled, and the energy of the fundamental mode is transferred to higher-frequency components. Furthermore, the higher harmonics become more pronounced as the models widen, the depth of submergence becomes shallower, and model porosity declines.

Analysis of Operating Deflection Shapes Based on Subspace Method

1997 ◽  
Author(s):  
Nobutaka Tsujiuchi ◽  
Yuichi Matsumura ◽  
Takayuki Koizumi
Keyword(s):  
Experimental Data ◽  
Time Domain ◽  
State Space Model ◽  
Measurement Data ◽  
Time Varying ◽  
Subspace Method ◽  
Identification Scheme ◽  
Space Model ◽  
Time Varying Systems ◽  
Frequency Components

Abstract In this paper, we propose the new method to identify the Operating Deflection Shapes (ODSs) from the measurement data of time domain. At first, we present the identification scheme of ODSs based on a state-space model. Then the scheme is extended to identify the ODSs adaptively for the time-varying systems by using the URV Decomposition (URVD). Proposed scheme is able to decompose the deformation of a structure under operating condition into the underlying superposition of well excited frequency components. This paper introduces the algorithm and shows the effectiveness of our proposed scheme applyed for both synthesized and experimental data.

A Coupled-Mode Technique for the Run-Up of Non-Breaking Dispersive Waves on Plane Beaches

2006 ◽  
Author(s):  
K. A. Belibassakis ◽  
G. A. Athanassoulis
Keyword(s):  
Shallow Water ◽  
Water Waves ◽  
Wave Equations ◽  
Neumann Boundary ◽  
Breaking Waves ◽  
Numerical Results ◽  
Coupled Mode Theory ◽  
Mode Theory ◽  
Coupled Mode ◽  
Run Up

A coupled-mode model is developed and applied to the transformation and run-up of dispersive water waves on plane beaches. The present work is based on the consistent coupled-mode theory for the propagation of water waves in variable bathymetry regions, developed by Athanassoulis & Belibassakis (1999) and extended to 3D by Belibassakis et al (2001), which is suitably modified to apply to a uniform plane beach. The key feature of the coupled-mode theory is a complete modal-type expansion of the wave potential, containing both propagating and evanescent modes, being able to consistently satisfy the Neumann boundary condition on the sloping bottom. Thus, the present approach extends previous works based on the modified mild-slope equation in conjunction with analytical solution of the linearised shallow water equations, see, e.g., Massel & Pelinovsky (2001). Numerical results concerning non-breaking waves on plane beaches are presented and compared with exact analytical solutions; see, e.g., Wehausen & Laitone (1960, Sec. 18). Also, numerical results are presented concerning the run-up of non-breaking solitary waves on plane beaches and compared with the ones obtained by the solution of the shallow-water wave equations, Synolakis (1987), Li & Raichlen (2002), and experimental data, Synolakis (1987).

scholarly journals PARAMETERIZATION OF EVOLUTION OF BIPHASE DURING NONLINEAR TRANSFORMATION OF WAVES IN COASTAL ZONE

2017 ◽  
pp. 3
Author(s):  
Yana Saprykina ◽  
Sergey Kuznetsov ◽  
Margarita Shtremel
Keyword(s):  
Experimental Data ◽  
Phase Shift ◽  
Coastal Zone ◽  
Energy Exchange ◽  
Wave Motion ◽  
Empirical Relation ◽  
Breaking Waves ◽  
Wave Transformation ◽  
Nonlinear Harmonics ◽  
Sloping Bottom

Based on experimental data, the problem of parametrization of spatial variation of the phase shift (biphase) between the first and second nonlinear harmonics of wave motion during wave transformation over sloping bottom in the coastal zone is discussed. It is revealed that the biphase values vary in the range [–π/2, π/2]. Biphase variations rigorously follow fluctuations in amplitudes of the first and second harmonics and the periodicity of energy exchange between them. The empirical relation applied in modern practice to calculate the biphase, which depends on the Ursell number, is incorrect for calculating the biphase for wave evolution in the coastal zone, because it does not take into account periodic energy exchange between the nonlinear harmonics. The new approximations of the biphase values for typical scenarios of wave transformations are suggested. It was demonstrated that the biphase of breaking waves defines breaking index and breaking type.

Research on dynamic characteristics and fatigue robust optimization of integrated vehicle model

2018 ◽  
Vol 232 (14) ◽  
pp. 1982-1999
Author(s):  
Bobo Li ◽  
Huiqun Yuan ◽  
Tianyu Zhao ◽  
Guangding Wang
Keyword(s):  
Experimental Data ◽  
Robust Optimization ◽  
Dynamic Characteristics ◽  
Six Sigma ◽  
Multiple Frequency ◽  
Heavy Duty ◽  
Vehicle Model ◽  
Design For Six Sigma ◽  
Frequency Components ◽  
Simulation Results

This paper investigates the dynamic characteristics and fatigue robust optimization of heavy-duty tractor. First, this paper presents a vehicle model with sub-structure method. Based on the theory of base motion, the structure dynamic characteristics are analyzed. Second, the accuracy of the method is verified by comparing the experimental results with the simulation results. Also, the dynamic response and the transfer function of vehicle are obtained using the above methods. Combined with the experimental data, the methods of random multiple frequency components and multi-axial fatigue life are adopted to analyze the fatigue damage of the heavy-duty tractor under different road conditions. Finally, the Design for Six Sigma is used to optimize the vehicle’s structure. The results show that by using the proposed method, the dynamic characteristics of the vehicle can be analyzed accurately and effectively, robustness of the vehicle can be improved, and mass of the vehicle can be reduced.

scholarly journals Detection of Breaking Waves in Single Wave Gauge Records of Surface Elevation Fluctuations

2019 ◽  
Vol 36 (9) ◽  
pp. 1863-1879 ◽  
Author(s):  
Dan Liberzon ◽  
Alexandru Vreme ◽  
Sagi Knobler ◽  
Itamar Bentwich
Keyword(s):  
Water Waves ◽  
Cost Effective ◽  
Breaking Waves ◽  
Recognition Algorithm ◽  
New Method ◽  
Surface Elevation ◽  
Detection Accuracy ◽  
Single Wave ◽  
Accurate Detection ◽  
Forced Waves

We report the development of a new method for accurate detection of breaking water waves that addresses the need for an accurate and cost-effective method that is independent of human decisions. The new detection method, which enables the detection of breakers using only surface elevation fluctuation measurements from a single wave gauge, supports the development of a new method for research relating to water waves and wind–wave interactions. According to the proposed method, detection is based on the use of the phase-time method to identify breaking-associated patterns in the instantaneous frequency variations of surface elevation fluctuations. A wavelet-based pattern recognition algorithm is devised to detect such patterns and provide accurate detection of breakers in the examined records. Validation and performance tests, conducted using both laboratory and open-sea data, including mechanically generated and wind-forced waves, are reported as well. These tests allow us to derive a set of parameters that assure high detection accuracy rates. The method is shown to be capable to achieve a positive detection rate exceeding 90%.

scholarly journals RUN-UP OF PERIODIC WAVES ON BEACHES OF NON-UNIFORM SLOPE

1984 ◽  
Vol 1 (19) ◽  
pp. 23 ◽  
Author(s):  
Yoshinobu Ogawa ◽  
Nobuo Shuto
Keyword(s):  
Experimental Data ◽  
Wave Theory ◽  
Breaking Waves ◽  
Lagrangian Description ◽  
Periodic Waves ◽  
Swash Zone ◽  
Slope Method ◽  
Long Wave ◽  
Run Up ◽  
Better Than

Run-up of periodic waves on gentle or non-uniform slopes is discussed. Breaking condition and run-up height of non-breaking waves are derived "by the use of the linear long wave theory in the Lagrangian description. As to the breaking waves, the width of swash zone and the run-up height are-obtained for relatively gentle slopes (less than 1/30), on dividing the transformation of waves into dissipation and swash processes. The formula obtained here agrees with experimental data better than Hunt's formula does. The same procedure is applied to non-uniform slopes and is found to give better results than Saville's composite slope method.

Free-Surface Measurements in a Tow Tank Using LiDAR

2009 ◽  
Author(s):  
Thomas C. Fu ◽  
Anne M. Fullerton ◽  
David A. Drazen
Keyword(s):  
Free Surface ◽  
Ocean Waves ◽  
Breaking Waves ◽  
Light Detection And Ranging ◽  
Spectral Content ◽  
Remote Sensing Technique ◽  
Lidar Measurements ◽  
Surface Measurements ◽  
Wave Profiles ◽  
White Water

Light Detection and Ranging, or LiDAR, is a remote sensing technique that can be utilized to collect topographic data. These systems have been used extensively to measure open ocean and ship generated waves. Recently LiDAR systems have been used to measure the transom wave of the R/V Athena I and ambient ocean waves. This work has primarily focused on providing the time averaged, and spectral content of the wave field, by scanning the laser to measure wave profiles evolving in time. This paper describes recent efforts to utilize LIDAR systems to measure free-surface elevations in laboratory tow tanks. LiDAR measurements are limited to the white-water breaking regions of the flow, due to the limited strength of the signal return from non-breaking regions. In extending LiDAR measurements to a laboratory tow tank environment the lack of surface roughness and hence the lack of surface light scatterers needed to be addressed. A number of laboratory measurement applications will be described including a tow tank measurement similar to the R/V Athena I effort, and also measurement of regular and irregular breaking waves.

scholarly journals Waves Trapped by Submerged Obstacles at High Frequencies

2007 ◽  
Vol 2007 ◽  
pp. 1-17 ◽  
Author(s):  
A. M. Marín ◽  
R. D. Ortíz ◽  
P. Zhevandrov
Keyword(s):  
Surface Water ◽  
Integral Equations ◽  
Water Waves ◽  
Trapped Modes ◽  
System Of Integral Equations ◽  
High Frequencies ◽  
Trapped Wave ◽  
Surface Water Waves ◽  
Horizontal Cylinders ◽  
Submerged Obstacles

As is well known, submerged horizontal cylinders can serve as waveguides for surface water waves. For large values of the wavenumberkin the direction of the cylinders, there is only one trapped wave. We construct asymptotics of these trapped modes and their frequencies ask→∞in the case of one or two submerged cylinders by means of reducing the initial problem to a system of integral equations on the boundaries and then solving them using a technique suggested by Zhevandrov and Merzon (2003).

The surface velocity field in steep and breaking waves

1988 ◽  
Vol 189 ◽  
pp. 1-22 ◽  
Author(s):  
W. K. Melville ◽  
Ronald J. Rapp
Keyword(s):  
Water Waves ◽  
Surface Displacement ◽  
Breaking Waves ◽  
Surface Velocity ◽  
Breaking Wave ◽  
Laser Anemometry ◽  
Air Water Interface ◽  
Velocity Spectra ◽  
Displacement Measurements ◽  
Surface Drift

Coincident simultaneous measurements of the surface displacement and the horizontal velocity at the surface of steep and breaking waves are presented. The measurements involve a novel use of laser anemometry at the fluctuating air-water interface and clearly show the limitations of surface displacement measurements in characterizing steep and breaking wave fields. The measurements are used to examine the evolution of the surface drift velocity, spectra, wave envelopes, and forced long waves in unstable deep-water waves. Preliminary results of this work were reported by Melville & Rapp (1983).

scholarly journals Interaction of Water Waves and a Submerged Parabolic Obstacle in the Presence of a Following Uniform/Shear Current Using RANS Model

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Yen-Lung Chen ◽  
Jing-Bo Hung ◽  
Shih-Lun Hsu ◽  
Shih-Chun Hsiao ◽  
Yuan-Chieh Wu
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Model ◽  
Analytical Solutions ◽  
Water Waves ◽  
Surface Deformation ◽  
Navier Stokes ◽  
Regular Waves ◽  
Uniform Shear ◽  
Shear Current

This paper simulates regular waves propagating over a submerged parabolic obstacle in the presence of a uniform/shear current using a two-dimensional numerical model, named COBRAS (Cornell Breaking and Structure). The numerical model solves the Reynolds-Averaged Navier-Stokes (RANS) equations and the free surface deformation is tracked using the volume of fluid method (VOF). The capability of the numerical model to simulate regular waves with a uniform or shear current over a constant water depth is first validated with available analytical solutions and experimental data. Comparisons among the experimental data, analytical solutions, and present numerical results show good agreements. Then, regular waves propagating over a submerged parabolic obstacle with a following current are investigated. Detailed discussions including those on the velocity and vorticity fields and the relation between free surface and vorticity are given.

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