Effect of Initial Acceleration on Ship Wave Pattern and Wake Survey Methods

1977 ◽  
Vol 21 (04) ◽  
pp. 239-247
Author(s):  
S. Calisal
Keyword(s):  
Survey Methods ◽  
Wave Pattern ◽  
Wave Resistance ◽  
Acceleration Wave ◽  
Ship Wave ◽  
Initial Acceleration ◽  
Wake Survey

Wave resistance calculations based on wave survey methods assume a constant ship velocity. The possible effects of initial acceleration are studied for different wave survey methods, and a procedure for determining the existence of an initial acceleration wave is proposed.

Some Experimental Results with Ship Model Acceleration Waves

1981 ◽  
Vol 25 (03) ◽  
pp. 181-190
Author(s):  
S. M. Çalisal
Keyword(s):  
Survey Methods ◽  
Wave Pattern ◽  
Wave Resistance ◽  
Pitching Moment ◽  
Total Resistance ◽  
Acceleration Waves ◽  
Acceleration Potential ◽  
Initial Acceleration ◽  
Theoretical Results ◽  
Independent Model

The wave resistance of a ship moving at a constant speed can be calculated using information obtained from its wave pattern. One of the basic assumptions in wave survey methods is t1he existence of a time-independent model speed. In towing tanks initial acceleration is unavoidable. Wehausen (1964) showed that the effect of initial acceleration on wave resistance has a decaying and oscillating character. Çalişal (1977) gave the general form of the initial acceleration potential and showed the existence of a two-dimensional wave of the formζT=AcTsin[14k0(x−cT)+ϕ(t)]+0(cT)−2(1)To study the validity of the theoretical results, some experiments were performed. The variation of the measured spectra and the frequencies within the recorded total resistance pitching moment are of interest. Results indicate that models should travel a distance proportional to the square of the Froude number before wave data collection can begin, that the predicted encounter frequency exists in the recorded total resistance and pitching moment signals, and that special effort is required to avoid initial acceleration waves due to wall effects.

On Ship Wave Patterns and Their Spectra

1971 ◽  
Vol 15 (01) ◽  
pp. 11-21 ◽  
Author(s):  
E. O. Tuck ◽  
J. I. Collins ◽  
W. H. Wells
Keyword(s):  
Wave Pattern ◽  
Wave Resistance ◽  
Two Dimensional ◽  
One Dimensional ◽  
Ship Wave ◽  
Wave Patterns ◽  
The One ◽  
Relationship Of ◽  
The Relationship

The one dimensional and two dimensional spectra of a ship wave pattern have been derived. It is shown that the spectra have distinct signatures containing information on speed, direction, shape, size, and wave resistance of the ship. The speed and direction are readily determined but the relationship of the spectrum to other ship characteristics requires further investigation. Some examples of detailed wave patterns in the wake of a parabolic sided ship have been computed.

Quasi-linear theory of waves and ship wave resistance in restricted waters

2004 ◽  
Vol 31 (10) ◽  
pp. 1231-1244 ◽  
Author(s):  
Eduard Amromin ◽  
Svetlana Kovinskaya ◽  
Igor Mizine
Keyword(s):  
Linear Theory ◽  
Wave Resistance ◽  
Ship Wave

scholarly journals The wave pattern of a doublet in a stream

1928 ◽  
Vol 121 (788) ◽  
pp. 515-523 ◽  
Keyword(s):  
Surface Effect ◽  
Ideal Point ◽  
Finite Size ◽  
Wave Pattern ◽  
Wave Resistance ◽  
Point Of View ◽  
The Body ◽  
Surface Elevation ◽  
More Care ◽  
Forced Waves

The following paper is a study of the surface waves caused by a doublet in a uniform stream, and in particular the variation in the pattern with the velocity of the stream or the depth of the doublet. In most recent work on this subject attention has been directed more to the wave resistance, which can be evaluated with less difficulty than is involved in a detailed study of the waves; in fact, it would seem that it is not necessary for that purpose to know the surface elevation completely, but only certain significant terms at large distances from the disturbance. Recent experimental work has shown con­siderable agreement between theoretical expressions for wave resistance and results for ship models of simple form, and attempts have been made at a similar comparison for the surface elevation in the neighbourhood of the ship. In the latter respect it may be necessary to examine expressions for the surface elevation with more care, as they are not quite determinate; any suitable free disturbance may be superposed upon the forced waves. For instance, it is well known that in a frictionless liquid a possible solution is one which gives waves in advance as well as in the rear of the ship, and the practical solution is obtained by superposing free waves which annul those in advance, or by some equivalent artifice. This process is simple and definite for an ideal point disturbance, but for a body of finite size or a distributed disturbance the complete surface elevation in the neighbourhood of the body requires more careful specification as regards the local part due to each element. It had been intended to consider some expressions specially from this point of view, but as the matter stands at present it would entail a very great amount of numerical calculation, and the present paper is limited to a much simpler problem although also involving considerable computation. A horizontal doublet of given moment is at a depth f below the surface of a stream of velocity c ; the surface effect may be described as a local disturbance symmetrical fore and aft of the doublet together with waves to the rear. Two points are made in the following work.

A Slender-Ship Theory of Wave Resistance

1983 ◽  
Vol 27 (01) ◽  
pp. 13-33
Author(s):  
Francis Noblesse
Keyword(s):  
Froude Number ◽  
Wave Resistance ◽  
Successive Approximations ◽  
Zeroth Order ◽  
Remarkable Effect ◽  
Ship Wave ◽  
First Order ◽  
Wigley Hull ◽  
Low Froude Number ◽  
The Waves

A new slender-ship theory of wave resistance is presented. Specifically, a sequence of explicit slender-ship wave-resistance approximations is obtained. These approximations are associated with successive approximations in a slender-ship iterative procedure for solving a new (nonlinear integro-differential) equation for the velocity potential of the flow caused by the ship. The zeroth, first, and second-order slender-ship approximations are given explicitly and examined in some detail. The zeroth-order slender-ship wave-resistance approximation, r(0) is obtained by simply taking the (disturbance) potential, ϕ, as the trivial zeroth-order slender-ship approximation ϕ(0) = 0 in the expression for the Kochin free-wave amplitude function; the classical wave-resistance formulas of Michell [1]2 and Hogner [2] correspond to particular cases of this simple approximation. The low-speed wave-resistance formulas proposed by Guevel [3], Baba [4], Maruo [5], and Kayo [6] are essentially equivalent (for most practical purposes) to the first-order slender-ship low-Froude-number approximation, rlF(1), which is a particular case of the first-order slender-ship approximation r(1): specifically, the first-order slender-ship wave-resistance approximation r(1) is obtained by approximating the potential ϕ in the expression for the Kochin function by the first-order slender-ship potential ϕ1 whereas the low-Froude-number approximation rlF(1) is associated with the zero-Froude-number limit ϕ0(1) of the potentialϕ(1). A major difference between the first-order slender-ship potential ϕ(1) and its zero-Froude-number limit ϕ0(1) resides in the waves that are included in the potential ϕ(1) but are ignored in the zero-Froude-number potential ϕ0(1). Results of calculations by C. Y. Chen for the Wigley hull show that the waves in the potential ϕ(1) have a remarkable effect upon the wave resistance, in particular causing a large phase shift of the wave-resistance curve toward higher values of the Froude number. As a result, the first-order slender-ship wave-resistance approximation in significantly better agreement with experimental data than the low-Froude-number approximation rlF(1) and the approximations r(0) and rM.

Wave Resistance and Wave Patterns of Thin Ships

1976 ◽  
Vol 20 (01) ◽  
pp. 1-6
Author(s):  
Joseph B. Keller ◽  
Daljit S. Ahluwalia
Keyword(s):  
Transverse Wave ◽  
Wave Pattern ◽  
Wave Resistance ◽  
Kelvin Waves ◽  
Profile Curve ◽  
Cylindrical Waves ◽  
Straight Line ◽  
Starting Point ◽  
Wave Patterns ◽  
Similar Pair

The wave resistance R and wave height h(x, z) are evaluated asymptotically for small Froude number F = U(gL)−½ for a slender hull of any shape. Michell's theory for a thin ship of length L moving with constant speed U along a straight line is the starting point. It is found that asymptotically R and h depend only upon four properties of the ship—the slope of the hull and the slope of the profile curve of the hull at the waterline at bow and stern. Simple formulas are obtained for R and h in terms of these slopes. The wave pattern consists of four waves—a longitudinal and a transverse wave from the bow and a similar pair from the stern. Their phases are the same as those of Kelvin waves due to pressure points at the bow and stern, and they also decay with distance like cylindrical waves. However, their amplitudes have different angular variations from those of Kelvin waves.

Improvements in the Prediction of the Characteristic Wave Pattern of Blunt Ships With Potential Codes

2013 ◽  
Author(s):  
Johannes Will ◽  
Jakob Christiansen
Keyword(s):  
Software Development ◽  
Viscous Flow ◽  
Potential Flow ◽  
Wave Pattern ◽  
Wave Resistance ◽  
Characteristic Wave ◽  
Ship Building

Potential flow solvers have been and still are the work horses of computational wave resistance determination. Having matured over more then two decades they seem to have reached their limit of improvement. While the main focus of today’s software development lies on viscous flow solvers, the development of potential codes must not be disregarded, but they should instead be keep up to date with respect to the requirements of today’s and future ship building markets as well as hardware and software capabilities.

Sign in / Sign up

Export Citation Format

Share Document