ON SHIPS WITH ZERO AND SMALL WAVE RESISTANCE

1963 ◽  
Author(s):  
B. Yim
Keyword(s):  
Wave Resistance ◽  
Small Wave

ABOUT FEATURES OF CHARACTERISTICS OF A SIGNAL OF THE ANGLE BEAM PROBE WITH COMPOSITE PIEZOPLATE AND VARIOUS TYPES PIEZOELECTRIC CERAMICS

2021 ◽  
pp. 6-16
Author(s):  
V. N. Danilov
Keyword(s):  
Electromechanical Coupling ◽  
Computer Modelling ◽  
Piezoelectric Ceramics ◽  
Wave Resistance ◽  
Coupling Coefficients ◽  
Intermediate Type ◽  
Maximal Amplitude ◽  
Additional Increase ◽  
Short Pulses ◽  
Small Wave

On the basis of computer modelling spectra and pulses of signals of the combined angle beam probe with composite piezoplate with piezoelectric ceramics several types it is shown, that short pulses with the greatest amplitudes are provided with use in piezoplate segnetosoft ceramics (for example, types PZT-5H, APC-850). At use piezoelectric ceramics intermediate type (CTS-19) the maximal amplitude of a pulse of the angle beam probe with such piezoplate appears much less, than for segnetosoft ceramics. Application in composite piezoplate piezoelectric ceramics such as TKS-21 (with the increased anisotropy of factors of electromechanical coupling coefficients) is inexpedient because of small amplitude of a pulse.Use of polymeric matrixes with small wave resistance provides additional increase of amplitude and reduction of length of pulses of angle beam probes.

Two Examples of Application of the Theory of Wave Resistance

1955 ◽  
Vol 1955 (77) ◽  
pp. 1-28
Author(s):  
Masao Kinoshita ◽  
Atsushi Abe ◽  
Shojiro Okada
Keyword(s):  
Wave Resistance

scholarly journals Hydrodynamic Forces Exerting on an Oscillating Cylinder under Translational Motion in Water Covered by Compressed Ice

Water ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 822
Author(s):  
Yury Stepanyants ◽  
Izolda Sturova
Keyword(s):  
Lift Force ◽  
Wave Motion ◽  
Translational Motion ◽  
Added Mass ◽  
Hydrodynamic Forces ◽  
Wave Resistance ◽  
Translational Velocity ◽  
Damping Coefficients ◽  
Incompressible Ideal Fluid ◽  
Theoretical Results

This paper presents the calculation of the hydrodynamic forces exerted on an oscillating circular cylinder when it moves perpendicular to its axis in infinitely deep water covered by compressed ice. The cylinder can oscillate both horizontally and vertically in the course of its translational motion. In the linear approximation, a solution is found for the steady wave motion generated by the cylinder within the hydrodynamic set of equations for the incompressible ideal fluid. It is shown that, depending on the rate of ice compression, both normal and anomalous dispersion can occur in the system. In the latter case, the group velocity can be opposite to the phase velocity in a certain range of wavenumbers. The dependences of the hydrodynamic loads exerted on the cylinder (the added mass, damping coefficients, wave resistance and lift force) on the translational velocity and frequency of oscillation were studied. It was shown that there is a possibility of the appearance of negative values for the damping coefficients at the relatively big cylinder velocity; then, the wave resistance decreases with the increase in cylinder velocity. The theoretical results were underpinned by the numerical calculations for the real parameters of ice and cylinder motion.

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.

scholarly journals Wake pattern and wave resistance for anisotropic moving disturbances

2014 ◽  
Vol 26 (9) ◽  
pp. 092106 ◽  
Author(s):  
Michael Benzaquen ◽  
Alexandre Darmon ◽  
Elie Raphaël
Keyword(s):  
Wave Resistance

Resistance of a Ship Undergoing Oscillatory Motion

2010 ◽  
Vol 54 (02) ◽  
pp. 120-132
Author(s):  
Lawrence J. Doctors ◽  
Alexander H. Day ◽  
David Clelland
Keyword(s):  
Finite Depth ◽  
Mean Value ◽  
Wave Resistance ◽  
General Effect ◽  
Towing Tank ◽  
Ship Model ◽  
Average Value ◽  
Unsteady Effects ◽  
Oscillatory Cycle ◽  
Resistance Tests

In this paper, we describe extensions to the research of Doctors et al. (Doctors, L. J., Day, A. H., and Clelland, D., 2008, Unsteady effects during resistance tests on a ship model in a towing tank, Journal of Ship Research, 52, 4, 263–273) and Day et al. (Day, A. H., Clelland, D., and Doctors, L. J., 2009, Unsteady finite-depth effects during resistance tests in a towing tank, Journal of Marine Science and Technology, 14, 3, 387–397) in which the oscillations in the wave resistance during the constant-velocity phase of a towing-tank resistance test on a ship model were measured and predicted, in the cases of relatively deep and relatively shallow water. In the current study, the ship model was towed with a harmonic velocity component superimposed on the usual constant forward velocity. This work constitutes a first step in the understanding of the unsteady hydrodynamics of a racing shell (rowing boat). We show here that the unsteady wave resistance varies considerably from the traditional (steady) average value. Indeed, the wave resistance is frequently negative during part of the oscillatory cycle. However, the general effect is an increase in the temporal mean value of the wave resistance; this suggests that every effort should be made to reduce the unsteadiness of the motion. We also demonstrate that the unsteady wave-resistance theory provides an excellent prediction of the measured effects summarized here. These predictions are often within a few percent of the measured values of the resistance.

Development and Assessment of a Total Resistance Optimized Bow for the AE 36

1994 ◽  
Vol 31 (02) ◽  
pp. 149-160
Author(s):  
Donald C. Wyatt ◽  
Peter A. Chang
Keyword(s):  
Experimental Data ◽  
Optimization Procedure ◽  
Wave Resistance ◽  
Scale Model ◽  
Optimization Approach ◽  
Nonlinear Constraints ◽  
Total Resistance ◽  
Hull Form ◽  
Final Design ◽  
Resistance Data

A numerically optimized bow design is developed to reduce the total resistance of a 23 000 ton ammunition ship (AE 36) at a speed of 22 knots. An optimization approach using slender-ship theory for the prediction of wave resistance is developed and applied. The new optimization procedure is an improvement over previous optimization methodologies in that it allows the use of nonlinear constraints which assure that the final design remains within practical limits from construction and operational perspectives. Analytic predictions indicate that the AE 36 optimized with this procedure will achieve a 40% reduction in wave resistance and a 33% reduction in total resistance at 22 knots relative to a Kracht elliptical bulb bow design. The optimization success is assessed by the analysis of 25th scale model resistance data collected at the David Taylor Research Center deepwater towing basin. The experimental data indicate that the optimized hull form yields a 51% reduction in wave resistance and a 12% reduction in total resistance for the vessel at 22 knots relative to the Kracht bulb bow design. Similarly encouraging results are also observed when comparisons are made with data collected on two other conventionally designed AE 36 designs.

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