scholarly journals WAVE-INDUCED OSCILLATIONS IN HARBORS WITH WAVE-ABSORBING QUAY

1984 ◽  
Vol 1 (19) ◽  
pp. 63
Author(s):  
Akinori Yoshida ◽  
Takeshi Ijima ◽  
Hideaki Okuzono
Keyword(s):  
Integral Equation ◽  
Velocity Potential ◽  
Side Wall ◽  
Source Distribution ◽  
Powerful Method ◽  
Variable Depth ◽  
Open Sea ◽  
The Fourier Transform ◽  
Wave Induced ◽  
Wave Reduction

An artificial wave-absorber (wave-absorbing quay) has come to be widely used to counteract excessive wave action on ships and structures in harbors. Its two-dimensional characteristics on wave absorption have been investigated with several types of the wave-absorbing quay theoretically as well as experimentally, e.g., Jarlan (5), Terret, Osorio and Lean (9), Ijima, Tanaka and Okuzono (3), and Ijima and Okuzono (4), but the effects on the wave reduction in harbors seem to be not fully clear. This may be due to the lack of analytical methods for solving wave-induced oscillations in harbors with the wave-absorbing quay. When the side wall in the harbor basin is assumed to be perfectly reflective, many theoretical methods for solving wave-induced oscillations in harbors have been presented: Ippen and Goda (2) solved the problem of a rectangular harbor by using the Fourier Transform technique. Hwang and Tuck (1) presented powerful method, which is applicable to arbitrary shaped harbors, by using integral equation (source distribution along the boundary) for the expression of the velocity potential. A similar method to that of Hwang and Tuck, but more suitable one for numerical computation, was presented by Lee (6), who used integral equation separately in the harbor basin and in the open sea. Raichlen and Naheer (8), Mattioli (7), and Yoshida and Ijima (10) presented the methods being applicable to the harbors of arbitrary shape and variable depth by further extending Lee's method.

scholarly journals WAVE INDUCED OSCILLATIONS OF HARBORS WITH VARIABLE DEPTH

1976 ◽  
Vol 1 (15) ◽  
pp. 203 ◽  
Author(s):  
F. Raichlen ◽  
E. Naheer
Keyword(s):  
Finite Difference ◽  
Helmholtz Equation ◽  
Numerical Method ◽  
Wave Energy ◽  
Water Surface ◽  
Two Dimensional ◽  
Variable Depth ◽  
Open Sea ◽  
Complex Shapes ◽  
Wave Induced

A numerical method is presented to treat the wave-induced oscillations of a harbor with a variable depth and width. A two-dimensional finite difference approach is used inside the harbor matched at the entrance to a solution for the open-sea based on the Helmholtz Equation which includes incident, reflected, and radiated wave energy. Examples of the response and the modal shapes of the water surface are presented for harbors with simple and complex shapes.

Scattering of SH Wave on Periodic Cracks in an Infinite Plane of Piezoelectric/Piezomagnic Composite Materials

2012 ◽  
Vol 166-169 ◽  
pp. 3364-3368
Author(s):  
Wei Shi ◽  
Li Xia Ma
Keyword(s):  
Stress Intensity Factor ◽  
Integral Equation ◽  
Composite Materials ◽  
Piezoelectric Materials ◽  
Infinite Plane ◽  
Sh Wave ◽  
Scattering Problems ◽  
Sh Waves ◽  
Periodic Cracks ◽  
The Fourier Transform

In this paper, the scattering problems of SH waves on periodic cracks in an infinite of piezoelectric/piezomagnic composite materials bonded to an infinite of homogeneous piezoelectric materials is investigated, the Fourier transform techniques are used to reduce the problem to the solution of Hilbert singular integral equation, the latter is solved by Lobotto-Chebyshev and Gauss integral equation, at last, numerical results showed the effect of the frequency of wave, sizes and so on upon the normalized stress intensity factor.

A STATISTICAL THEORY OF APERTURE SYNTHESIS

1967 ◽  
Vol 45 (6) ◽  
pp. 2041-2052
Author(s):  
Ralph J. Gagnon
Keyword(s):  
Point Source ◽  
Random Noise ◽  
Circular Disk ◽  
Brightness Distribution ◽  
Source Distribution ◽  
Base Line ◽  
Fourier Inversion ◽  
Visibility Function ◽  
The Fourier Transform ◽  
Infinite Set

The usual methods of interferometry make use of the Fourier transform relationship which holds between a radio-noise brightness distribution and the complex visibility function which is measured with a pair of antennas. The visibility function is a function of the distance or base line between the antennas. If it were known for all base lines, then the brightness distribution could be found by Fourier inversion. Unfortunately, the visibility function is not known for all base lines and the Fourier inversion is not unique. If the observer wishes to interpret his data by displaying a single possible brightness distribution, then he must choose from the infinite set of brightness distributions which could have produced his data. Previously, the author suggested that this be accomplished by representing the set of possible distributions as a statistical ensemble, and making the choice on a statistical basis so as to minimize the expected mean-square error.In the present communication, the results of the previous paper are presented for the two-dimensional case. The inversion formulas are worked out in detail for the cases of uniform point-source distributions in a square (or rectangle) and in a circular disk, and also for a point-source distribution with a Gaussian envelope taper. It is shown how to extend the point-source results to a distribution of nonpoint sources, and as an example the inversion equations are computed for the case of a distribution of Gaussian-shaped sources distributed with a Gaussian amplitude or density envelope. Finally, the appropriate inversion equations are derived for an observed visibility function which is contaminated with additive zero-mean Gaussian random noise, uncorrelated with the true visibility function.

A Hybrid Integral Equation Method for Wave Forces on Three-Dimensional Offshore Structures

1987 ◽  
Vol 109 (3) ◽  
pp. 229-236 ◽  
Author(s):  
M. M. F. Yuen ◽  
F. P. Chau
Keyword(s):  
Integral Equation ◽  
Velocity Potential ◽  
Three Dimensional ◽  
Integral Equation Method ◽  
Offshore Structures ◽  
Equation Method ◽  
Wave Forces ◽  
Test Cases ◽  
Outer Domain ◽  
Hybrid Integral

Wave forces on arbitrary-shaped three-dimensional offshore structures are analyzed by the proposed hybrid integral equation method. Eigenfunction expansion is used to represent velocity potential in the outer domain, while a set of integral equations is developed for the inner domain encompassing the structure. A floating dock and a step cylinder are used as test cases showing the validity of the method.

Three-Dimensional Periodic Fully Nonlinear Potential Waves

2013 ◽  
Author(s):  
Dmitry Chalikov ◽  
Alexander V. Babanin
Keyword(s):  
Wave Field ◽  
Degrees Of Freedom ◽  
Velocity Potential ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Transform Method ◽  
Fully Nonlinear ◽  
Stokes Waves ◽  
Nonlinear Potential ◽  
The Fourier Transform

An exact numerical scheme for a long-term simulation of three-dimensional potential fully-nonlinear periodic gravity waves is suggested. The scheme is based on a surface-following non-orthogonal curvilinear coordinate system and does not use the technique based on expansion of the velocity potential. The Poisson equation for the velocity potential is solved iteratively. The Fourier transform method, the second-order accuracy approximation of the vertical derivatives on a stretched vertical grid and the fourth-order Runge-Kutta time stepping are used. The scheme is validated by simulation of steep Stokes waves. The model requires considerable computer resources, but the one-processor version of the model for PC allows us to simulate an evolution of a wave field with thousands degrees of freedom for hundreds of wave periods. The scheme is designed for investigation of the nonlinear two-dimensional surface waves, for generation of extreme waves as well as for the direct calculations of a nonlinear interaction rate. After implementation of the wave breaking parameterization and wind input, the model can be used for the direct simulation of a two-dimensional wave field evolution under the action of wind, nonlinear wave-wave interactions and dissipation. The model can be used for verification of different types of simplified models.

scholarly journals Splash formation at the nose of a smoothly curved body in a stream

1999 ◽  
Vol 40 (4) ◽  
pp. 421-436 ◽  
Author(s):  
E. O. Tuck ◽  
S. T. Simakov
Keyword(s):  
Integral Equation ◽  
Free Surface ◽  
Velocity Potential ◽  
Integral Form ◽  
The Body ◽  
Front Face ◽  
Separation Condition ◽  
Polygonal Approximation ◽  
Side Condition ◽  
Two Dimensional Flow

AbstractIn two-dimensional flow past a body close to a free surface, the upwardly diverted portion may separate to form a splash. We model the nose of such a body by a semi-infinite obstacle of finite draft with a smoothly curved front face. This problem leads to a nonlinear integral equation with a side condition, a separation condition and an integral constraint requiring the far-upstream free surface to be asymptotically plane. The integral equation, called Villat's equation, connects a natural parametrisation of the curved front face with the parametrisation by the velocity potential near the body. The side condition fixes the position of the separation point, whereas the separation condition, known as the Brillouin-Villat condition, imposes a continuity relation to be satisfied at separation. For the described flow we derive the Brillouin-Villat condition in integral form and give a numerical solution to the problem using a polygonal approximation to the front face.

Wave-induced oscillations in harbours of variable depth

1978 ◽  
Vol 6 (3) ◽  
pp. 161-172 ◽  
Author(s):  
Franco Mattioli
Keyword(s):  
Variable Depth ◽  
Wave Induced

Validating the Coupling of Multibody Dynamic Simulations With Sea Keeping Simulations

2013 ◽  
Author(s):  
Stephan D. A. Hannot ◽  
Jan G. Los ◽  
Bram A. W. van Spaendonk ◽  
Alex B. Kruijswijk ◽  
Albert C. L. de Krijger
Keyword(s):  
Surface Wave ◽  
Theory Development ◽  
Simulation Tool ◽  
Floating Structure ◽  
Dynamic Simulations ◽  
Open Sea ◽  
Multibody Dynamic ◽  
Development And Validation ◽  
Wave Induced ◽  
Important Design

Dredging is the activity of excavating soil or other sediments from the bottom of a water body such as a lake or sea. The purpose of dredging varies: e.g. maintaining the depth of waterways or obtaining material for beach nourishment. Most ‘dredgers’ are composed of a floating structure (ship or pontoon) on which the dredging equipment that is used to excavate at the seabed is installed. Dredging at open sea, offshore dredging, becomes a more common operating condition. This means that dredgers will have to be designed with surface wave induced motions and forces in mind. Therefore simulating the motions of dredgers due to surface waves coupled with the motion of the dredging equipment is an important design analysis step. This requires a tool that can simulate a coupled sea keeping and multibody dynamic problem. In this work the theory, development and validation of such a simulation tool are discussed.

The Lift of Twisted and Cambered Wings in Supersonic Flow

1955 ◽  
Vol 6 (2) ◽  
pp. 149-163 ◽  
Author(s):  
G. N. Lance
Keyword(s):  
Integral Equation ◽  
Velocity Potential ◽  
Free Stream ◽  
Delta Wing ◽  
Complete Solution ◽  
Symmetric Potential ◽  
Leading Edges ◽  
Limiting Case ◽  
The Given ◽  
Stream Direction

SummaryA generalised conical flow theory is used to deduce an integral equation relating the velocity potential on a delta wing (with subsonic leading edges) to the given downwash distribution over the wing. The complete solution of this integral equation is derived. This complete solution is composed of two parts, one being symmetric and the other anti-symmetric with respect to the span wise co-ordinate; each part represents a velocity potential. For example, if y is the spanwise co-ordinate and x is measured in the free stream direction, then a downwash of the form w= - α11 Ux|y| is symmetric and will give rise to a symmetric potential, whereas w= - α11 Ux|y| sgn y is anti-symmetric and gives rise to an anti-symmetric potential. The velocity potentials of such flows are given in the form of Tables for all downwashes up to and including homogenous cubics in the spanwise and streamwise co-ordinates. Table III gives similar formulae in the limiting case when the leading edges become transonic; these are compared with results given elsewhere and serve as a check on the results of Tables I and II.

Hydrodynamic Study on Added Resistance Using Unsteady Wave Analysis

2013 ◽  
Vol 57 (04) ◽  
pp. 220-240
Author(s):  
Masashi Kashiwagi
Keyword(s):  
Direct Measurement ◽  
Incident Wave ◽  
Ship Motions ◽  
Analysis Method ◽  
Added Resistance ◽  
Wave Analysis ◽  
Linear Superposition ◽  
The Fourier Transform ◽  
Wave Induced ◽  
Incident Waves

It is known that the added resistance in waves can be computed from ship-generated unsteady waves through the unsteady wave analysis method. To investigate the effects of nonlinear ship-generated unsteady waves and bluntness of the ship geometry on the added resistance, measurements of unsteady waves, wave-induced ship motions, and added resistance were carried out using two different (blunt and slender) modified Wigley models. The ship-generated unsteady waves are also produced by the linear superposition using the waves measured for the diffraction and radiation problems and the complex amplitudes of ship motions measured for the motion-free problem in waves. Then a comparison is made among the values of the added resistance by the direct measurement using a dynamometer and by the wave analysis method using the Fourier transform of measured and superposed waves. It is found that near the peak of the added resistance where ship motions become large, the degree of nonlinearity in the unsteady wave becomes prominent, especially at the forefront part of the wave. Thus, the added resistance evaluated with measured waves at larger amplitudes of incident wave becomes much smaller than the values by the direct measurement and by the wave analysis with superposed waves or measured waves at smaller amplitude of incident wave. Discussion is also made on the characteristics of the added resistance in the range of short incident waves.

Sign in / Sign up

Export Citation Format

Share Document