scholarly journals Wave Exciting Forces Acting on a Ship Travelling in Following Seas

1983 ◽  
Vol 1983 (154) ◽  
pp. 129-140 ◽  
Author(s):  
Masashi Kashiwagi
Keyword(s):  
Following Seas ◽  
Exciting Forces ◽  
Wave Exciting Forces

Theory of Short Wave Excitation

1986 ◽  
Vol 30 (03) ◽  
pp. 147-152
Author(s):  
Yong Kwun Chung
Keyword(s):  
Incident Wave ◽  
Characteristic Length ◽  
Finite Depth ◽  
Short Wave ◽  
The Body ◽  
Wave Number ◽  
Floating Body ◽  
Wave Excitation ◽  
Exciting Forces ◽  
Wave Exciting Forces

When the wavelength of the incident wave is short, the total surface potential on a floating body is found to be 2∅ i & O (m-l∅ i) on the lit surface and O (m-l∅ j) on the shadow surface where ~b i is the potential of the incident wave and m the wave number in water of finite depth. The present approximation for wave exciting forces and moments is reasonably good up to X/L ∅ 1 where h is the wavelength and L the characteristic length of the body.

scholarly journals Wave Exciting Forces on Groups of Floating Bodies

1979 ◽  
Vol 1979 (145) ◽  
pp. 79-87 ◽  
Author(s):  
Akira Masumoto ◽  
Yoshio Yamagami ◽  
Ryuji Sakata
Keyword(s):  
Floating Bodies ◽  
Exciting Forces ◽  
Wave Exciting Forces

Experimental Investigation of the First and Second Order Wave Exciting Forces on a Restrained Body in Long Crested Irregular Waves

2011 ◽  
Author(s):  
Joa˜o Pessoa ◽  
Nuno Fonseca ◽  
Suresh Rajendran ◽  
C. Guedes Soares
Keyword(s):  
Experimental Investigation ◽  
Transfer Functions ◽  
Vertical Cylinder ◽  
Vertical Axis ◽  
Second Order ◽  
The Body ◽  
Irregular Waves ◽  
Numerical Predictions ◽  
Exciting Forces ◽  
Wave Exciting Forces

The paper presents an experimental investigation of the first order and second order wave exciting forces acting on a body of simple geometry subjected to long crested irregular waves. The body is axis-symmetric about the vertical axis, like a vertical cylinder with a rounded bottom, and it is restrained from moving. Second order spectral analysis is applied to obtain the linear spectra, coherence spectra and cross bi-spectra of both the incident wave elevation and of the horizontal and vertical wave exciting forces. Then the linear and quadratic transfer functions (QTF) of the exciting forces are obtained. The QTF obtained from the analysis of irregular wave measurements are compared with results from experiments in bi-chromatic waves and with numerical predictions from a second order potential flow code.

Forward-Speed Vertical Wave Exciting Forces on Ships

1985 ◽  
Vol 29 (02) ◽  
pp. 105-111
Author(s):  
P. D. Sclavounos
Keyword(s):  
Velocity Potential ◽  
Reverse Flow ◽  
Diffraction Problem ◽  
Three Dimensional ◽  
Forward Speed ◽  
Direct Solution ◽  
Radiation Problem ◽  
Strip Theory ◽  
Exciting Forces ◽  
Wave Exciting Forces

Expressions are derived for the heave and pitch exciting force and moment on a ship advancing in waves. They are obtained in the form of an integral over the ship axis of the outer source strength of the reverse-flow radiation problem multiplied by the value of the incident-wave velocity potential. Their performance is tested for two slender spheroids. Comparisons are made with predictions obtained from a three-dimensional numerical solution at zero speed—the expression common to strip-theory programs which uses the ship hull as the integration surface—and the direct solution of the diffraction problem.

Motion Studies of a Vessel with Water on Deck

1981 ◽  
Vol 18 (01) ◽  
pp. 38-50
Author(s):  
Jeff Dillingham
Keyword(s):  
Time Domain ◽  
Equations Of Motion ◽  
Random Choice ◽  
Nonlinear Hyperbolic System ◽  
Random Choice Method ◽  
Exciting Forces ◽  
Wave Exciting Forces ◽  
Energy Dissipators ◽  
Motion Studies ◽  
The Time Domain

The seakeeping characteristics of a small fishing vessel are investigated. The type of vessel under consideration has a large flat deck which may, under severe considerations, remain partially or totally awash. We consider the effect of such deck water on the vessel motions. The vessel is considered as a two-degree-of-freedom system and the equations of motion in sway and roll are formulated in the time domain using an impulse response technique. Formulation of the problem of describing the flow of the deck water leads to a nonlinear hyperbolic system of equations. An approximate solution to these equations is obtained numerically using the random-choice method, also known as Glimm's method. From this solution the static and dynamic forces exerted on the vessel by the deck water are computed. These forces are then added to the external wave exciting forces to obtain a complete time-domain solution for the motion of the vessel and the deck water. We examine the effect of several simple changes in ship geometry. In most cases the deck water is found to act as a rather effective roll-damping mechanism. This is a result of the frequent appearance of hydraulic jumps which act as energy dissipators. The greatest reduction in roll was achieved by adding a small amount of camber to the deck. Variations in scupper geometry did not have very great effects on the rolling motion.

Wave Exciting Forces of a Free Floating Semi Submersible in Regular Waves

2015 ◽  
Vol 74 (5) ◽  
Author(s):  
Hassan Abyn ◽  
Mohammad Rafiqul Islam ◽  
Jaswar Jaswar ◽  
Amin Mahmoudi ◽  
C. L. Siow ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Domain Analysis ◽  
Offshore Structures ◽  
Source Distribution ◽  
Linear Wave ◽  
Distribution Method ◽  
Exciting Forces ◽  
Domain Models ◽  
Wave Exciting Forces

Drilling and production of oil by semi submersible take place in many locations throughout the world. Generally, floating structures play an important role in exploring the oil and gas from the sea. The force and motion prediction of offshore structures may be carried out using time domain or frequency domain models or model tests. In this paper the frequency domain analysis used because it is the simplified and linearized form of the equations of motion. The time domain analysis, unlike frequency domain models, is adequate to deal with non-linearities such as viscous damping and mooring forces, but it requires sophisticated solution techniques and it is expensive to employ. In this paper, the wave exciting forces of a free floating semi-submersible were carried out using 3D source distribution method within the scope of the linear wave theory. The results obtained from computations were also compared with the results obtained using commercial software MOSES and WAMIT.  

The Motions of a Ship on a Sloped Seabed

2006 ◽  
Author(s):  
Bas Buchner
Keyword(s):  
Water Depth ◽  
Diffraction Theory ◽  
Added Mass ◽  
Interference Effects ◽  
Large Size ◽  
Correct Calculation ◽  
Exciting Forces ◽  
Wave Exciting Forces ◽  
Local Water ◽  
Drift Forces

In standard diffraction theory it is assumed that the water depth is constant and that the seabed is infinitely large. To account for a local varying bathymetry in shallow water (as it can occur for offshore LNG terminals) it is sometimes considered to introduce a second fixed body on the seabed representing this bathymetry in diffraction theory. Based on the results presented in this paper it can be concluded that this is (without special measures) not possible. The refraction and interference effects are too strong and affect the wave exciting forces on the LNG carrier in an incorrect way. A large size of the second body and smoother edges of this body do not improve the situation. However, a second body in diffraction theory, when chosen properly with respect to size and shape, can contribute to the correct calculation of the added mass and damping of vessels on sloped seabeds as this varies with the local water depth over the length of the vessel. This will clearly affect the motion response of the vessel. This can be seen for instance in the pitch-heave coupling. This will influence the motions of the ship in waves, as well as the resulting drift forces and related mooring loads.

Sign in / Sign up

Export Citation Format

Share Document