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.

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.

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.

Potential flow and forces for incompressible viscous flow

1992 ◽  
Vol 437 (1901) ◽  
pp. 517-525 ◽  
Keyword(s):  
Circular Cylinder ◽  
Viscous Flow ◽  
Solid Body ◽  
Potential Flow ◽  
Physical Significance ◽  
Inertial Forces ◽  
Incompressible Viscous Flow ◽  
Ellipsoid Of Revolution ◽  
Finite Body ◽  
Uniform Stream

Forces on a finite body in an incompressible viscous flow are shown to be contributed by a potential flow and fluid elements of non-zero vorticity in a revealing formulation. The present study indicates that the potential flow play also a geometric role in determining the contribution of the fluid elements. Consideration is given to a solid body moving through a fluid, fluid accelerating past a solid body and a solid body which oscillates in a uniform stream. The effects of induced-mass and inertial forces appear naturally in the formulation and are separated from the contribution due to the surface vorticity and that due to the vorticity within the flow. Physical significance of the present analysis for vortical flows about a finite body is illustrated by examples, e.g. flow past a circular cylinder or an ellipsoid of revolution.

Explicit Approximations for Calculating Potential Flow About a Body

1983 ◽  
Vol 27 (01) ◽  
pp. 1-12
Author(s):  
F. Noblesse ◽  
G. Triantafyllou
Keyword(s):  
Free Surface ◽  
Potential Flow ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Wave Resistance ◽  
Two Dimensional ◽  
Regular Waves ◽  
Practical Applications ◽  
Flow Problems ◽  
Unbounded Fluid

Several explicit approximations for calculating nonlifting potential flow about a body in an unbounded fluid are studied. These approximations are shown to be exact in the particular cases of flows due to translations of ellipsoids, and they are compared with the exact potential for two-dimensional flows about ogives in translatory motions. Two approximations, given by formulas (31) and (32) in the conclusion, appear to be of particular interest for practical applications, and they can be extended to free-surface flow problems, for example, ship wave resistance, and radiation and diffraction of regular waves by a body.

Low-Aspect-Ratio Flat Ship Theory for Moderate Froude Numbers

1991 ◽  
Vol 35 (04) ◽  
pp. 325-330
Author(s):  
S. L. Cole
Keyword(s):  
Aspect Ratio ◽  
Froude Number ◽  
Potential Flow ◽  
Order Term ◽  
Leading Edge ◽  
Wave Resistance ◽  
Intermediate Region ◽  
Leading Order ◽  
Cross Sectional ◽  
Low Aspect Ratio

Low-aspect-ratio flat ship theory models ships whose dimensions satisfy draft << beam <<length. This paper systematically derives the inner and outer linearized problems for moderate Froude number potential flow past such a ship and their solutions. These solutions are matched through an intermediate region. It is found that the leading-order term for the wave resistance for moderate speed low-aspectratio flat ship theory is the same as found in slender ship theory for ships with equivalent cross-sectional areas. Flat ship theory, however, predicts singularities in the flow along the outside of the ship's leading edge which are not present in slender ship theory. A simple example demonstrating these spurious singularities is worked out.

Zero wave resistance for ships moving in shallow channels at supercritical speeds

1997 ◽  
Vol 335 ◽  
pp. 305-321 ◽  
Author(s):  
XUE-NONG CHEN ◽  
SOM DEO SHARMA
Keyword(s):  
Shallow Water ◽  
Water Channel ◽  
Wave Theory ◽  
Wave Pattern ◽  
Wave Resistance ◽  
Kp Equation ◽  
Nonlinear Case ◽  
Hull Form ◽  
Ship Waves ◽  
Shallow Channel

This paper deals with the wave pattern and wave resistance of a slender ship moving steadily at supercritical speed in a shallow water channel. Using, successively, linear and nonlinear shallow-water wave theory it is demonstrated that, if the hull form is adapted to speed and channel geometry according to certain rules, the ship waves can be made to form a localized pattern around the ship that moves at the same speed as the ship and at the same time the associated wave resistance can be made to vanish. In the nonlinear case, the zero-wave-resistance ship hull is derived from a KP equation solution of the oblique interaction of two identical solitons. This astonishing phenomenon may be called shallow-channel superconductivity.

Improvements in the Prediction of the Wave Making Resistance From Potential Flow by Using Transverse Wave Cut Methods

2015 ◽  
Author(s):  
Johannes Will ◽  
Anja Kömpe
Keyword(s):  
Transverse Wave ◽  
Potential Flow ◽  
Wave Resistance ◽  
New Approach ◽  
Operational Costs ◽  
Correct Determination ◽  
Major Shortcoming ◽  
Resistance Prediction ◽  
Major Factors

The reliable and correct determination of the wave resistance is the key to an efficient ship design, as the wave resistance is one on the major factors concerning building and operational costs. In this paper the authors present a new approach to transverse wave cut analysis to overcome the major shortcoming of the resistance prediction from potential flow: a numerically stable and physically sound estimate for the magnitude of the wave making resistance.

Sign in / Sign up

Export Citation Format

Share Document