scholarly journals Generation of solitary waves by forward- and backward-step bottom forcing

2001 ◽  
Vol 432 ◽  
pp. 341-350 ◽  
Author(s):  
DAO-HUA ZHANG ◽  
ALLEN T. CHWANG
Keyword(s):  
Solitary Waves ◽  
Water Surface ◽  
Bottom Topography ◽  
Surface Region ◽  
Resistance Coefficient ◽  
Wave Resistance ◽  
Wave System ◽  
Two Dimensional ◽  
Wave Emission ◽  
Generation Period

A finite difference method based on the Euler equations is developed for computing waves and wave resistance due to different bottom topographies moving steadily at the critical velocity in shallow water. A two-dimensional symmetric and slowly varying bottom topography, as a forcing for wave generation, can be viewed as a combination of fore and aft parts. For a positive topography (a bump), the fore part is a forward-step forcing, which contributes to the generation of upstream-advancing solitary waves, whereas the aft part is a backward-step forcing to which a depressed water surface region and a trailing wavetrain are attributed. These two wave systems respectively radiate upstream and downstream without mutual interaction.For a negative topography (a hollow), the fore part is a backward step and the aft part is a forward step. The downstream-radiating waves generated by the backward-step forcing at the fore part will interact with the upstream-running waves generated by the forward-step forcing at the aft. Therefore, the wave system generated by a negative topography is quite different from that by a positive topography. The generation period of solitary waves is slightly longer and the instantaneous drag fluctuation is skewed for a negative topography. When the length of the negative topography increases, the oscillation of the wave-resistance coefficient with time does not coincide with the period of solitary wave emission.

scholarly journals Examination of Eggers’ Relationship Between Transverse Wave Profiles and Wave Resistance

1967 ◽  
Vol 11 (04) ◽  
pp. 240-256
Author(s):  
H. E. Kobus
Keyword(s):  
Conformal Mapping ◽  
Cross Section ◽  
Transverse Wave ◽  
Basic Assumption ◽  
Small Error ◽  
Wave Resistance ◽  
Wave System ◽  
Two Dimensional ◽  
Free Wave ◽  
Wave Profiles

A two-dimensional vertical strut with a cross section obtained by conformal mapping of an ogive in an unbounded plane into a channel has been investigated. Eggers' relationship between transverse wave profiles and wave resistance has been applied to both analytical and experimental profiles. The basic assumption of a free wave system in the analysis seems to introduce only a small error in comparison to the effects of viscosity.

Hydrodynamic Power Radiated by a Heaving and Pitching Air-Cushion Vehicle

1978 ◽  
Vol 22 (02) ◽  
pp. 67-79 ◽  
Author(s):  
Lawrence J. Doctors
Keyword(s):  
Steady State ◽  
Critical Speed ◽  
Three Dimensional ◽  
Wave Resistance ◽  
Wave System ◽  
Two Dimensional ◽  
Similar Magnitude ◽  
Frequency Condition ◽  
Air Cushion ◽  
Air Cushion Vehicle

The harmonic heave and pitch motion of an air-cushion vehicle traveling at a constant speed over water is studied here, with a view to determining the power radiated by the surrounding wave system. The planform of the particular craft considered is compartmented into forward and aft subcushions, and the fluctuations of pressure in these are utilized to represent the effect of the vehicle on the water. The usual linearized incompressible potential flow theory is used. The calculations show that at typical Froude numbers and encounter frequencies, considerable power can be radiated in this manner, and it is generally of similar magnitude to the power required to overcome the usual steady-state wave resistance. Surprisingly, the singularity in the linear theory that occurs at the critical speed-frequency condition was found to be extremely localized and is therefore only significant in the case of a two-dimensional pressure band, or in the case of a three-dimensional pressure patch, at low Froude numbers.

scholarly journals WATER WAVES DUE TO A LOCAL DISTURBANCE

2011 ◽  
Vol 1 (6) ◽  
pp. 8
Author(s):  
J. E. Prins
Keyword(s):  
Water Waves ◽  
Water Surface ◽  
Wave Pattern ◽  
Wave System ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Local Disturbance ◽  
Wave Characteristics ◽  
Two Dimensional Model ◽  
Made In

A model investigation of the characteristics of waves generated by a local disturbance was made in order to obtain comparison with the theories of UNOKI and NAKANO (1953) and KRANZER and KELLER (1955). The two-dimensional model for the case of initial local elevation or depression of uniform height of the water surface showed that certain wave characteristics such as phase periods and "interference" pattern could be described reasonably well within certain limits of water depth and height and extent of the disturbed area. Beyond those limits the leading part separated from the generated wave pattern as a solitary wave or a more complicated wave system. For a certain range of conditions the leading part was preceded by a bore during the first portion of the travel.

scholarly journals Some cases of wave motion due to a submerged obstacle

1917 ◽  
Vol 93 (654) ◽  
pp. 520-532 ◽  
Keyword(s):  
Circular Cylinder ◽  
Wave Motion ◽  
Fluid Pressure ◽  
Wave Pattern ◽  
Wave Resistance ◽  
Dimensional Case ◽  
Small Radius ◽  
Wave System ◽  
Two Dimensional ◽  
Submerged Sphere

1. As far as I am aware, only one case of wave motion caused by a submerged obstacle has been worked out in any detail, namely the two-dimensional motion due to a circular cylinder; for this case, Prof. Lamb has given a solution applicable when the cylinder is of small radius and is at a considerable depth. The method can be extended to bodies of different shape, and my object in this paper is to work out the simplest three-dimensional case, the motion of a submerged sphere. The problem I have considered specially is the wave resistance of the submerged body. In the two-dimensional case, this is calculated by considerations of energy and work applied to the train of regular waves. But for a moving sphere the wave system is more complicated, like the well-known wave pattern for a moving point disturbance, and similar methods are not so easily applied; I have therefore calculated directly the horizontal resultant of the fluid pressure on the sphere. Before working out this case, the analysis for the circular cylinder is repeated, because it is necessary to carry the approximation a stage further than in Prof. Lamb’s solution in order to verify that the resultant horizontal pressure on the cylinder is the same as the wave resistance obtained by the method of energy.

Comparison principles for free-surface flows with gravity

1991 ◽  
Vol 230 ◽  
pp. 231-243 ◽  
Author(s):  
Walter Craig ◽  
Peter Sternberg
Keyword(s):  
Solitary Waves ◽  
Finite Depth ◽  
Free Surface Flows ◽  
Immiscible Fluids ◽  
Steady Flows ◽  
Two Dimensional ◽  
Surface Flows ◽  
Ship Hulls ◽  
Geometrical Information ◽  
Supercritical Flows

This article considers certain two-dimensional, irrotational, steady flows in fluid regions of finite depth and infinite horizontal extent. Geometrical information about these flows and their singularities is obtained, using a variant of a classical comparison principle. The results are applied to three types of problems: (i) supercritical solitary waves carrying planing surfaces or surfboards, (ii) supercritical flows past ship hulls and (iii) supercritical interfacial solitary waves in systems consisting of two immiscible fluids.

Separation of Enantiomers and Racemate Formation in Two-Dimensional Crystals at the Water Surface from Racemic α-Amino Acid Amphiphiles:  Design and Structure

1997 ◽  
Vol 119 (5) ◽  
pp. 933-942 ◽  
Author(s):  
Isabelle Weissbuch ◽  
Maria Berfeld ◽  
Wim Bouwman ◽  
Kristian Kjaer ◽  
Jens Als-Nielsen ◽  
...  
Keyword(s):  
Amino Acid ◽  
Water Surface ◽  
Two Dimensional ◽  
Separation Of Enantiomers
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