The refraction of head seas by a long ship

1975 ◽  
Vol 67 (4) ◽  
pp. 689-703 ◽  
Author(s):  
F. Ursell
Keyword(s):  
Cross Section ◽  
Axial Direction ◽  
Wave Pattern ◽  
Horizontal Cylinder ◽  
Constant Speed ◽  
Constant Cross Section ◽  
Kelvin Wave ◽  
The Waves

It is known that head seas cannot travel without deformation along a horizontal cylinder of full constant cross-section. Calculations are given which indicate that the waves are refracted away from the axis of the cylinder. Similar refraction effects are found for waves generated by a pulsating source on the cylinder, and also for the Kelvin wave pattern generated by a long ship of nearly constant cross-sectiop moving with constant speed in the axial direction.

scholarly journals Graphical analysis of free-surface wave fields from moving two consecutive posts connected by thin plate

2020 ◽  
Vol 2020 (1) ◽  
pp. 45-53
Author(s):  
Pavel Bimberekov
Keyword(s):  
Wave Field ◽  
Water Transport ◽  
Cross Section ◽  
Thin Plate ◽  
Wave Pattern ◽  
Graphical Analysis ◽  
Wave System ◽  
Kelvin Wave ◽  
Horizontal Section ◽  
Shaped Cross Section

The article presents photographic materials of wave pictures from two consecutive posts of teardrop cross-section and the same posts with a thin plate installed between them, which introduces into consideration not only separate sequentially moving sources, but also reunites them into a single object, interacting along its entire length with the system of waves from the first source. The regularities of the wave field of consecutive posts with a plate in-stalled between them by means of graphic processing are considered. The possibility of finding the front imaginary source of the Kelvin wave pattern forming the ship's wave system at the position of both one and two wave-lengths in front of the top of the bow retaining wave is estimated. A method is proposed for determining the position of the fictitious location of the aft Kelvin wave system of the ship's wave system based on the results of the analysis of the wave field at the characteristic speeds of movement, leading to the most successfully fixed inter-location of the wave pattern from the bow and aft extremities. There are shown the pictures of moving forward a pair of posts with a blunt end of a horizontal section at the same speed and photo fixation from a close angle, pictures of moving forward the posts with a plate between them with a blunt end of a teardrop-shaped cross section at a low speed, moving forward posts with a plate at the side with a sharp end of a teardrop-shaped cross section, etc. All presented photographs were taken in the experimental pool of the Siberian state University of water transport (Novosibirsk state Academy of water transport) in 2006.

The phase configuration of waves around a body moving in a rotating stratified fluid

1976 ◽  
Vol 75 (4) ◽  
pp. 647-656 ◽  
Author(s):  
K. S. Peat ◽  
T. N. Stevenson
Keyword(s):  
Wave Theory ◽  
Wave Pattern ◽  
Horizontal Cylinder ◽  
Constant Angular Velocity ◽  
Circular Path ◽  
Rotating Fluid ◽  
Amplitude Wave ◽  
Special Cases ◽  
Fluid Theory ◽  
The Waves

A body is started impulsively from rest and moves on an arbitrary path in an incompressible, stably stratified, rotating fluid. The phase configuration of the waves which are generated is studied using small amplitude wave theory. The theory is compared with experiment for a few special cases which include a horizontal cylinder (a) oscillating about a position fixed in the fluid, (b) moving with constant velocity and (c) moving with a constant angular velocity in a circular path relative to the fluid. Theory and experiment show reasonable agreement except where wakes interfere with the wave pattern.

The refraction of head seas by a long ship. Part 2. Waves of long wavelength

1977 ◽  
Vol 82 (4) ◽  
pp. 643-657 ◽  
Author(s):  
F. Ursell
Keyword(s):  
Eigenvalue Problem ◽  
Cross Section ◽  
Cross Sections ◽  
Wave Amplitude ◽  
Infinite Cylinder ◽  
Constant Cross Section ◽  
Circular Section ◽  
Long Wavelength ◽  
Apparent Inconsistency ◽  
The Waves

It is known that head seas cannot travel without deformation along a cylinder of full constant cross-section, and recent calculations have indicated that the wave amplitude near the cylinder ultimately decreases as the waves travel along the cylinder, i.e. that the waves are refracted away from the axis of the cylinder. It was assumed in these calculations that the cross-section was a half-immersed circle of radius a of the same order as the wavelength 2π/K, but the method can probably be adapted to arbitrary full constant cross-sections. (There is however another calculation which indicates that for a thin ship the wave amplitude ultimately increases.) In the present paper these calculations are extended. The circular section is again studied but it is now supposed that the wavenumber Ka may be small. Uniformly valid expressions for the wave potential are obtained which show that for small Ka the refraction becomes significant only when Kx (the dimensionless distance along the cylinder) is so large that the product (Kx)½ v0(Ka) is also large; here the function v0(Ka) ∼ 2Ka arises in the solution of a certain eigenvalue problem. (The uniformly valid expressions also suggest an interpretation of the thin-ship calculation which resolves the apparent inconsistency.) The same method is applied to the waves generated by a pulsating source on an infinite cylinder, and similar results are obtained.

Effects of openings on the seismic behavior and performance level of concrete shear walls

2019 ◽  
Author(s):  
Hossein Alimohammadi ◽  
Mostafa Dalvi Esfahani ◽  
Mohammadali Lotfollahi Yaghin
Keyword(s):  
Static Analysis ◽  
Cross Section ◽  
Seismic Behavior ◽  
Shear Walls ◽  
Shear Wall ◽  
Constant Cross Section ◽  
Added Resistance ◽  
Different Shapes ◽  
And Performance ◽  
Abaqus Software

In this study, the seismic behavior of the concrete shear wall considering the opening with different shapes and constant cross-section has been studied, and for this purpose, several shear walls are placed under the increasingly non-linear static analysis (Pushover). These case studies modeled in 3D Abaqus Software, and the results of the ductility coefficient, hardness, energy absorption, added resistance, the final shape, and the final resistance are compared to shear walls without opening.

Condensation in a Variable Acceleration Field and the Condensing Thermosyphon

1965 ◽  
Vol 87 (4) ◽  
pp. 355-360 ◽  
Author(s):  
J. C. Chato
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Radial Distance ◽  
Constant Cross Section ◽  
Linear Variation ◽  
Temperature Differential ◽  
Acceleration Field ◽  
Nusselt Numbers ◽  
Increasing Temperature ◽  
Limiting Values

The general problem of condensation in a variable acceleration field was investigated analytically. The case of the linear variation, which occurs in a constant cross section, rotating thermosyphon, was treated in detail. The results show that the condensate thickness and Nusselt numbers approach limiting values as the radial distance increases. The effects of the temperature differential and the Prandtl number are similar to those in other condensation problems; i.e., the heat transfer increases slightly with increasing temperature differential if Pr > 1, but it decreases with increasing temperature differential if Pr ≪ 1.

Turbulent buoyant convection from a source in a confined region

1969 ◽  
Vol 37 (1) ◽  
pp. 51-80 ◽  
Author(s):  
W. D. Baines ◽  
J. S. Turner
Keyword(s):  
Point Source ◽  
Cross Section ◽  
Laboratory Experiments ◽  
Region Of Interest ◽  
Constant Cross Section ◽  
General Shape ◽  
Turbulent Environment ◽  
Starting Conditions ◽  
Upward Velocity ◽  
Local Mean

This paper considers the effect of continuous convection from small sources of buoyancy on the properties of the environment when the region of interest is bounded. The main assumptions are that the entrainment into the turbulent buoyant region is at a rate proportional to the local mean upward velocity, and that the buoyant elements spread out at the top of the region and become part of the non-turbulent environment at that level. Asymptotic solutions, valid at large times, are obtained for the cases of plumes from point and line sources and also periodically released thermals. These all have the properties that the environment is stably stratified, with the density profile fixed in shape, changing at a uniform rate in time at all levels, and everywhere descending (with ascending buoyant elements).The analysis is carried out in detail for the point source in an environment of constant cross-section. Laboratory experiments have been conducted for this case, and these verify the major predictions of the theory. It is then shown how the method can be extended to include more realistic starting conditions for the convection, and a general shape of bounded environment. Finally, the model is applied quantitatively to a variety of problems in engineering, the atmosphere and the ocean, and the limitations on its use are discussed.

Deflection of Beams of Varying Cross Section

1937 ◽  
Vol 4 (2) ◽  
pp. A49-A52
Author(s):  
Miklós Hetényi
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Original Problem ◽  
New Method ◽  
Constant Cross Section ◽  
Deflection Curve ◽  
Force System ◽  
Uniform Cross Section ◽  
The Cross

Abstract This paper calls attention to a new method of dealing with deflections of beams, the cross sections of which vary by steps. It is shown that the effect of this variation on the shape of the deflection curve can be represented by a properly chosen force system acting on a beam of uniform cross section. There is no approximation involved in this substitution, whereby the original problem is reduced to one of computing deflections of beams of constant cross section.

Essence of Electric Charge of elementary particles according of New axioms and Laws

2020 ◽  
Vol 3 (4) ◽  
Keyword(s):  
Electromagnetic Field ◽  
Electron Pair ◽  
Constant Speed ◽  
Longitudinal Vortex ◽  
Uniform Motion ◽  
Variable Velocity ◽  
Variable Speed ◽  
External Observer ◽  
Closed Circle ◽  
The Waves

Two new Axioms and eight new Laws have been proposed and developed in previous reports. This report uses both axioms and only four laws. According to the first axiom (Axiom1), we can replace uniform motion in a closed circle with non-uniform motion in an open vortex. According to the second axiom (Axiom2), there are pairs of vortices that are mutually orthogonal or they tend to work in a system by a special type of resonance. Of all the variants of vortex pairs, the most probable is the pair: accelerating vortex from the center outwards connected with a delayed vortex from the periphery inwards. This pair is a model of the connected proton-electron pair. The behavior of a free electron and a proton in an Electromagnetic Field is studied. Actually like a cross vortex from outside to inside the electron will be directed to the positive pole. Therefore, an external observer who does not know what the internal structure of the electron is will think and will be deceived that the electron carries a negative charge. The exact opposite is observed for the proton. The properties of a system of linked electrons and protons are also studied. It is known that the Electromagnetic Field propagates at a constant speed and when pulsating the waves are only transverse. According to the new Axioms and Laws in the electron-proton system, the internal connections are of variable speed and when pulsating, the waves are not only transverse and longitudinal. Because the Electromagnetic field is only transverse at a constant speed , it appears that the interaction between the proton and the electron is not Electromagnetic but some other interaction. The interaction between the protons includes cross vortex with variable velocity and longitudinal vortex with variable velocity

Nozzles for Supersonic Flow Without Shock Fronts

1944 ◽  
Vol 11 (2) ◽  
pp. A93-A100
Author(s):  
Ascher H. Shapiro
Keyword(s):  
Cross Section ◽  
Compressible Fluids ◽  
Three Dimensions ◽  
Infinite Length ◽  
Constant Cross Section ◽  
Nozzle Design ◽  
Wave Fronts ◽  
A Value ◽  
Parallel Stream ◽  
Shock Fronts

Abstract Flow patterns for compressible fluids at supersonic velocities are discussed, and it is shown that shock fronts form when neighboring Mach lines (envelopes of wave fronts originating from point disturbances) intersect. A criterion for divergence of Mach lines is developed for cases in which the passage is symmetrical in two or three dimensions and has a straight axis. This criterion is used as the basis for designing supersonic nozzles and diffusers. The analysis indicates that only a nozzle of infinite length can discharge a parallel stream into a tube of constant cross section without the formation of shock fronts. Methods are presented for designing nozzles of finite length, with the intensity of shock fronts reduced to as small a value as possible, and it is shown that nozzles of reasonable length may be designed so that shock fronts are insignificant. Experimental observations indicate that the proposed method of nozzle design is a practical one. With regard to supersonic diffusers having a straight axis, it is shown that shock fronts cannot be avoided, even though the diffuser is of infinite length. However, the methods of this paper may be used as an aid in determining the best diffuser design.

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