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.

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.

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 Partitioning Graph Drawings and Triangulated Simple Polygons into Greedily Routable Regions

2017 ◽  
Vol 27 (01n02) ◽  
pp. 121-158 ◽  
Author(s):  
Martin Nöllenburg ◽  
Roman Prutkin ◽  
Ignaz Rutter
Keyword(s):  
Routing Protocol ◽  
Graph Drawing ◽  
Geographic Routing ◽  
Np Hard ◽  
Line Drawings ◽  
Simple Polygons ◽  
Straight Line ◽  
Starting Point ◽  
Minimum Decomposition ◽  
Geographic Routing Protocol

A greedily routable region (GRR) is a closed subset of [Formula: see text], in which any destination point can be reached from any starting point by always moving in the direction with maximum reduction of the distance to the destination in each point of the path. Recently, Tan and Kermarrec proposed a geographic routing protocol for dense wireless sensor networks based on decomposing the network area into a small number of interior-disjoint GRRs. They showed that minimum decomposition is NP-hard for polygonal regions with holes. We consider minimum GRR decomposition for plane straight-line drawings of graphs. Here, GRRs coincide with self-approaching drawings of trees, a drawing style which has become a popular research topic in graph drawing. We show that minimum decomposition is still NP-hard for graphs with cycles and even for trees, but can be solved optimally for trees in polynomial time, if we allow only certain types of GRR contacts. Additionally, we give a 2-approximation for simple polygons, if a given triangulation has to be respected.

Wave-Island Interactions About Circular Artificial Islands

1984 ◽  
Vol 106 (1) ◽  
pp. 113-119 ◽  
Author(s):  
J. M. Niedzwecki
Keyword(s):  
Closed Form ◽  
Water Depth ◽  
Wave Breaking ◽  
Numerical Procedure ◽  
Wave Pattern ◽  
The Arctic ◽  
Ray Theory ◽  
Closed Form Solutions ◽  
Wave Patterns ◽  
Dimensionless Formulation

The behavior of waves interacting with islands has gained renewed interest with the construction of exploratory drilling islands in the Arctic. This paper focuses upon the behavior of waves incident upon axisymmetric islands characterized by circular contours which vary with water depth. The island profiles of Arthur and Pocinki, which have closed form solutions, and a single tier conical island are examined. A new dimensionless formulation of Arthur’s ray theory and an extremely accurate numerical procedure to evaluate the ray integrals are presented. It is shown that each island profile leads to a distinct wave pattern about the island. These wave patterns are presented in figures which portray the wave capture and wave breaking about circular islands. It is intended that the methodology presented be used to initially assess trends and to evaluate the need for more refined analyses.

124 Ovarian follicular development and steroid secretion during oestrous cycle of Lohi sheep

2020 ◽  
Vol 32 (2) ◽  
pp. 189
Author(s):  
M. Younis ◽  
M. Irfan-ur-Rehman Khan ◽  
A. Murtaza ◽  
M. Abbas ◽  
M. Z. Tahir ◽  
...  
Keyword(s):  
Peak Plasma ◽  
Prostaglandin F2α ◽  
Follicular Development ◽  
Wave Pattern ◽  
Oestrous Cycle ◽  
Maximum Diameter ◽  
Corpora Lutea ◽  
Plasma Progesterone ◽  
Preovulatory Follicles ◽  
Wave Patterns

Pakistan has 30.9 million heads of sheep; however, little information is available on their reproductive aspects. The objective of this study was to document ovarian physiology and endocrinology of Lohi ewes during the oestrous cycle. Nine Lohi ewes, synchronized by administering single prostaglandin F2α (PGF2a; Cyclomate, Star Laboratories), were monitored for ovarian follicular dynamics using transrectal ultrasonography (7.5MHz, HS-1500, Honda) for two consecutive oestrous cycles during the breeding season (September to November 2018). Changes in plasma progesterone and oestradiol-17β concentrations of ewes (n=9) were also determined during the oestrous cycle using radioimmunoassay. The interovulatory interval of Lohi ewes averaged 17.0±0.1 days, and the duration of follicular and luteal phases was 4.6±0.2 and 11.3±0.2 days, respectively. Follicles emerged in either 3- or 4-wave patterns, but the frequency of the 3-wave pattern was higher than that of the 4-wave (87 vs. 13%, respectively; P=0.05). Following ovulation (Day 0), follicles (=3mm) in 3-wave cycles (n=14) emerged on Days 0.7, 5.2, and 10.5, whereas in 4-wave cycles (n=2) follicles emerged on Days 0.1, 4, 8.5, and 11.5. The maximum diameter of preovulatory follicles and corpora lutea (CL) were 5.4±0.3 and 10.4±0.3mm, respectively. Regardless of the wave pattern, single ovulation occurred in each cycle. The CL was first detectable on Day 4±0.1, it reached maximum diameter on Day 9±0.1, and luteolysis began on Day 12.2±0.2 of the cycle. The peak plasma oestradiol-17β concentration (42.5±2.6 pgmL−1) was observed 48h before ovulation and correlated with the diameter of the preovulatory follicle during the follicular phase (r=0.84; P<0.05). The peak plasma progesterone concentration (11.8±1.7ngmL−1) was observed on Day 9±0.1 and coincided with the diameter of CL throughout the oestrous cycle (r=0.93; P<0.05). In conclusion, the majority of oestrous cycles in Lohi ewes had a 3-wave pattern and were mono-ovulatory in nature.

On the calculation of wave patterns

1972 ◽  
Vol 53 (4) ◽  
pp. 637-645 ◽  
Author(s):  
C. Hunter
Keyword(s):  
Gravity Waves ◽  
Stratified Fluid ◽  
Circular Path ◽  
Straight Line ◽  
Wave Patterns ◽  
Single Process ◽  
The Waves

The calculation of the pattern of waves produced by a point disturbance in a steady field which may be non-uniform can be performed straightforwardly by a single process of integration along the characteristic rays. For illustration, the method is applied to gravity waves produced by a source moving either in a straight line or in a circular path, to the symmetrical waves produced by a source in an expanding sheet and to the waves resulting from an instantaneous disturbance in :I stratified fluid.

Experimental and theoretical study of shock wave propagation through double-bend ducts

2001 ◽  
Vol 437 ◽  
pp. 255-282 ◽  
Author(s):  
O. IGRA ◽  
X. WU ◽  
J. FALCOVITZ ◽  
T. MEGURO ◽  
K. TAKAYAMA ◽  
...  
Keyword(s):  
Shock Wave ◽  
Wave Attenuation ◽  
Wave Pattern ◽  
Complex Flow ◽  
Shock Wave Attenuation ◽  
Planar Shock ◽  
Wave Patterns ◽  
Planar Shock Wave ◽  
Flow Evolution ◽  
Interferometric Study

The complex flow and wave pattern following an initially planar shock wave transmitted through a double-bend duct is studied experimentally and theoretically/numerically. Several different double-bend duct geometries are investigated in order to assess their effects on the accompanying flow and shock wave attenuation while passing through these ducts. The effect of the duct wall roughness on the shock wave attenuation is also studied. The main flow diagnostic used in the experimental part is either an interferometric study or alternating shadow–schlieren diagnostics. The photos obtained provide a detailed description of the flow evolution inside the ducts investigated. Pressure measurements were also taken in some of the experiments. In the theoretical/numerical part the conservation equations for an inviscid, perfect gas were solved numerically. It is shown that the proposed physical model (Euler equations), which is solved by using the second-order-accurate, high-resolution GRP (generalized Riemann problem) scheme, can simulate such a complex, time-dependent process very accurately. Specifically, all wave patterns are numerically simulated throughout the entire interaction process. Excellent agreement is found between the numerical simulation and the experimental results. The efficiency of a double-bend duct in providing a shock wave attenuation is clearly demonstrated.

SPATIAL SYMMETRIES AND GEOMETRICAL PHASES IN CLASSICAL DISSIPATIVE SYSTEMS

1993 ◽  
Vol 07 (02) ◽  
pp. 71-82 ◽  
Author(s):  
A. S. LANDSBERG
Keyword(s):  
Reaction Diffusion ◽  
Wave Pattern ◽  
Dissipative Systems ◽  
Spatial Shift ◽  
Finite Dimensional ◽  
Reaction Diffusion Model ◽  
Traveling Wave Front ◽  
Wave Patterns ◽  
Standard Reaction ◽  
Continuum Systems

We describe the emergence of geometrical phases in dissipative systems with continuous spatial symmetries. The phase characterizes the spatial shift of a wave pattern that arises as the result of a cyclic adiabatic transport of control parameters of the system. Geometrical phases are calculated for both stationary and propagating wave patterns. Complementary formulations are provided for finite-dimensional and continuum systems. The theory is used to determine the phase shift for a traveling wave front in a standard reaction-diffusion model.

scholarly journals ANALYSIS OF THE EFFECT OFWAVE PATTERNS ON REFRACTION IN AIRBORNE LIDAR BATHYMETRY

2016 ◽  
Vol XLI-B1 ◽  
pp. 133-139 ◽  
Author(s):  
P. Westfeld ◽  
K. Richter ◽  
H.-G. Maas ◽  
Robert Weiß
Keyword(s):  
Water Body ◽  
Wave Pattern ◽  
Airborne Lidar ◽  
Beam Divergence ◽  
Wave Patterns ◽  
Wave Effects ◽  
Local Wave ◽  
Airborne Lidar Bathymetry ◽  
Coordinate Correction ◽  
Random Part

This contribution investigates the effects of wave patterns on 3D point coordinate accuracy in LiDAR bathymetry. The finite diameter refracted laser pulse path passing the air/water interface is modelled differentially and in a strict manner. Typical wave patterns are simulated and their impact on the 3D coordinates at the bottom of the water body are analysed. It can be shown that the effects of waves within small LiDAR bathymetry footprints on the depth and planimetry coordinates is significant. Planimetric effects may reach several decimetres or even metres, and depth coordinate errors also reach several decimetres, even in case of horizontal water body bottom. The simplified assumption of averaging wave effects often made in many ALB applications is not only fulfilled in cases of a very large beam divergence under certain wave pattern conditions. Modern smaller beam divergence systems will mostly experience significant wave pattern dependent coordinate errors. The results presented here thus form a basis for a more strict coordinate correction if the wave pattern can be modelled from the LiDAR bathymetry water surface reflections or other observations. Moreover, it will be shown that the induced coordinate errors contain systematic parts in addition to the local wave surface dependent quasi-random part, which allows for the formulation of wave pattern type dependent correction terms.

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