scholarly journals DETERMINATION OF THE WAVE HEIGHT IN NATURE FROM MODEL TESTS SUPPLEMENTED BY CALCULATION

2011 ◽  
Vol 1 (6) ◽  
pp. 12
Author(s):  
J. G.H.R. Diephuis ◽  
J. G. Gerritze
Keyword(s):  
Shallow Water ◽  
Wave Height ◽  
Deep Water ◽  
Bottom Topography ◽  
Model Tests ◽  
Small Scale ◽  
Wave Characteristics ◽  
Sea Bottom ◽  
The Waves

This paper deals with the problem of determining the wave characteristics in shallow water from those in deep water. In general this can be done by means of a refraction calculation. If the sea bottom topography is too irregular the height of the waves can be determined by means of a small-scale refraction model. In both cases, however, some additional effects have to be taken into account, viz. the influence of the bottom friction and the influence of the wind.

scholarly journals MODEL TESTS ON THE BELATIONSHIP BETWEEN DEEP--WATEB WAVE CHARACTERISTICS AND LONGSHORE CURRENTS

1964 ◽  
Vol 1 (9) ◽  
pp. 11 ◽  
Author(s):  
Arthur Brebner ◽  
J.W. Kamphus
Keyword(s):  
Wave Height ◽  
Deep Water ◽  
Water Wave ◽  
Model Tests ◽  
Shore Line ◽  
Beach Slope ◽  
Wave Characteristics ◽  
Longshore Currents ◽  
Deep Water Wave

It has Long been recognized that the movement of Littoral material takes place, in the main, in the onshore regions of a beach where breaking of waves occurs. Waves whose crests in deep water make an angLe o(a with the shore Line, and which break at an angLe C*© , are the mam source of energy for the generation of the forces which manifest themselves in Long-shore currents and the resulting LittoraL transport. This littoraL materiaL is put into motion before, during and after breaking but it is extremeLy difficult to separate the effects of the forces and currents in these three zones. In what foLlows the authors have attempted to measure the intensity of the current around the breaking zone in a highLy ideaLized beach model in which the shore Line is straight, has a constant beach sLope, 0, and is attacked by waves of constant deep-water wave-height, HQ, and period, T. During refraction and shoaLing the angLe of the wave-crests with the shore-Line is reduced from o

Resistance Tests of an Articulated Pusher Barge System in Deep and Shallow Water

2021 ◽  
Author(s):  
Li Zhang ◽  
Lei Xing ◽  
Mingyu Dong ◽  
Weimin Chen
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
Deep Water ◽  
Water Resistance ◽  
Model Tests ◽  
System 2 ◽  
Changing Trend ◽  
The Difference ◽  
Transport Vessel ◽  
Resistance Performance

Abstract Articulated pusher barge vessel is a short-distance transport vessel with good economic performance and practicability, which is widely used in the Yangtze River of China. In this present work, the resistance performance of articulated pusher barge vessel in deep water and shallow water was studied by model tests in the towing tank and basin of Shanghai Ship and Shipping Research Institute. During the experimental investigation, the articulated pusher barge vessel was divided into three parts: the pusher, the barge and the articulated pusher barge system. Firstly, the deep water resistance performance of the articulated pusher barge system, barge and the pusher at design draught T was studied, then the water depth h was adjusted, and the shallow water resistance at h/T = 2.0, 1.5 and 1.2 was tested and studied respectively, and the difference between deep water resistance and shallow water resistance at design draught were compared. The results of model tests and analysis show that: 1) in the study of deep water resistance, the total resistance of the barge was larger than that of the articulated pusher barge system. 2) for the barge, the shallow water resistance increases about 0.4–0.7 times at h/T = 2.0, 0.5–1.1 times at h/T = 1.5, and 0.7–2.3 times at h/T = 1.2. 3) for the pusher, the shallow water resistance increases about 1.0–0.4 times at h/T = 2.7, 1.2–0.9 times at h/T = 2.0, and 1.7–2.4 times at h/T = 1.6. 4) for the articulated pusher barge system, the shallow water resistance increases about 0.2–0.3 times at h/T = 2.0, 0.5–1.3 times at h/T = 1.5, and 1.0–3.5 times at h/T = 1.2. Furthermore, the water depth Froude number Frh in shallow water was compared with the changing trend of resistance in shallow water.

scholarly journals PROBABILITIES OF BREAKING WAVE CHARACTERISTICS

1970 ◽  
Vol 1 (12) ◽  
pp. 25 ◽  
Author(s):  
J. Ian Collins
Keyword(s):  
Shallow Water ◽  
Probability Density ◽  
Deep Water ◽  
Surf Zone ◽  
Probability Distributions ◽  
Rayleigh Distribution ◽  
Breaking Wave ◽  
Wave Characteristics ◽  
Probability Densities ◽  
Wave Heights

Utilizing the hydrodynamic relationships for shoaling and refraction of waves approaching a shoreline over parallel bottom contours a procedure is developed to transform an arbitrary probability density of wave characteristics in deep water into the corresponding breaking characteristics in shallow Water A number of probability distributions for breaking wave characteristics are derived m terms of assumed deep water probability densities of wave heights wave lengths and angles of approach Some probability densities for wave heights at specific locations in the surf zone are computed for a Rayleigh distribution in deep water The probability computations are used to derive the expectation of energy flux and its distribution.

scholarly journals ‘Underkeel Clearance’

1968 ◽  
Vol 21 (1) ◽  
pp. 91-91
Author(s):  
J. A. Ewing
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Ship Motion ◽  
Water Effects ◽  
The Waves

I would like to comment on the change in underkeel clearance due to the motion of a ship in a seaway (A. F. Dickson, this Journal, 20, 363).Captain Dickson, in his conclusions, states that known techniques do not allow underkeel clearance to be calculated when ship motion is present. In fact there are a number of reliable ways of calculating the motions of a ship in waves (for example References (1) and (2), which treat the case of pitch and heave) which may help in this problem. These methods usually assume the ship is in deep water and is heading directly into the waves which are further assumed to be long-crested; but I believe it may also be possible to make reliable calculations for shallow-water effects and for waves which are, in reality, short-crested.

scholarly journals Taphonomy and ecology of deep-water Ediacaran organisms from northwestern Canada

1992 ◽  
Vol 6 ◽  
pp. 219-219 ◽  
Author(s):  
Guy M. Narbonne ◽  
Robert W. Dalrymple
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Microbial Mats ◽  
Bedding Plane ◽  
Thin Layers ◽  
Sea Bottom ◽  
Windermere Supergroup ◽  
Storm Wave ◽  
Upper Slope

Although most occurrences of Ediacaran fossils are from shallow-shelf deposits, taxonomically-similar assemblages have recently been described from a 2.5 km-thick succession of dark mudstones and turbiditic sandstones in the Windermere Supergroup of the Mackenzie Mountains, northwestern Canada. The paleogeographic position (20-40 km seaward of the shelf edge), abundant evidence of mass flow, and the complete absence of in situ shallow-water features imply that deposition took place on a slope considerably below storm wave-base. Ediacaran fossils were not observed in axial trough deposits (lower parts of the Twitya and Sheepbed formations), but megafossils occur sporadically in lower to middle slope deposits higher in the same formations. Megafossils and trace fossils are present in upper slope settings (Blueflower Formation) at the top of the Ediacaran succession. The megafossil assemblage varies stratigraphically, but in all formations is dominated by discoid forms (e.g. Cyclomedusa, Ediacaria, Nimbia); frondose forms and vendomiids are very rare.Megafossils are preserved mainly as positive features on the soles of thin turbidite beds. Most fossiliferous beds begin with the rippled layer of the turbidite (Tc), but a few begin with the graded (Ta) or parallel-laminated (Tb) layer. Consistent orientation and high relief of individuals, evidence of mutual deformation during growth of adjacent organisms, and other taphonomic features imply that virtually all of the taxa represent benthic polypoid and frond-like organisms (not jellyfish). Slump structures occur commonly in the sandstone fill of fossils, suggesting that many of the organisms were buried alive by the turbidite and later decomposed. Other individuals, even on the same bedding plane, exhibit graded to laminated fill identical to that of the overlying turbidite bed, indicating that the depressions on the sea bottom produced by these individuals were empty at the time of turbidite deposition. Escape structures are absent, suggesting that the Ediacaran organisms were not capable of burrowing up through even thin layers of sand.Ediacaran megafossils are invariably preserved on black, wrinkled surfaces similar to those elsewhere interpreted as microbial mats. Molding of delicate features (including tentacles), preservation of open molds as negative epireliefs, and sedimentological evidence of considerable cohesion of these surfaces relative to the underlying turbiditic muds (Td,e) supports this interpretation, and suggests that microbial mats were as important in the preservation of these deep-water Ediacara faunas as they were in their shallow-water equivalents. The presence of the wrinkled mats and their associated Ediacaran fossils almost exclusively in the pyritic intervals of the succession suggests that both may have lived under exaerobic conditions in this deep-water setting.

SUBCRITICAL WAVE WAKE UNSTEADINESS

2021 ◽  
Vol 153 (A3) ◽  
Author(s):  
A Robbins ◽  
G A Thomas ◽  
M R Renilson ◽  
G J Macfarlane ◽  
I W Dand
Keyword(s):  
Shallow Water ◽  
Wave Height ◽  
Deep Water ◽  
Hull Form ◽  
Non Linear ◽  
Water Effects ◽  
Wave Angle ◽  
Soliton Generation

Vessel wave wake in deep water is well understood, shallow water less so, specifically the effect of restricted water. This operational zone is highly dynamic and non-linear in nature, thus being worthy of closer examination. The paper reviews the primary mechanisms for unsteadiness in wave wake: starting acceleration and soliton generation. A comprehensive set of experiments was conducted using an NPL catamaran hull form to investigate unsteadiness in both wave height and wave angle. The results show that the unsteadiness was primarily due to soliton generation, and that blockage has a significant effect. As a result, additional metrics, aimed at defining shallow water effects in the transcritical region, are proposed.

Experimental Research on Horizontal Rotation of Remotely Operated Vehicles Induced by External Forces Near the Surface of the Ocean

2009 ◽  
Vol 43 (3) ◽  
pp. 5-12
Author(s):  
Tomoya Inoue ◽  
Hiroyoshi Suzuki ◽  
Tsuyoshi Shimamura ◽  
Kengo Nakajima ◽  
Genki Shioji
Keyword(s):  
Wave Height ◽  
Experimental Research ◽  
Wake Flow ◽  
Water Tank ◽  
Remotely Operated Vehicle ◽  
Wave Characteristics ◽  
Propeller Wake ◽  
Wave Effects ◽  
External Forces ◽  
The Waves

AbstractWhen a remotely operated vehicle (ROV) is lowered from its support vessel by a cable, it rotates horizontally because of external forces as it nears the surface of the ocean. This causes the cable to twist. This paper describes experiments using a model of the ROV ABISMO in a water tank to improve safety by examining the waves and the wake flow of propellers as possible causes of the external twisting forces. These experiments on wave effects evaluated the effect of wave height, wavelength, and submerged depth of the model. In addition, the model was varied to include different configurations of fins and outer covers. The experiments on the effect of propeller wake flow evaluated the effect of the horizontal propeller offset and the submerged model depth. The horizontal rotation of the ROV induced by the waves and the wake flow was observed in some cases. The results showed that the wave characteristics, offset, and submerged depth all influenced the generation of horizontal rotation. It was also found that the addition of a horizontal fin and extended vertical fins reduced the horizontal rotation.

On the vorticity transport due to dissipating or breaking waves in shallow-water flow

2000 ◽  
Vol 407 ◽  
pp. 235-263 ◽  
Author(s):  
OLIVER BÜHLER
Keyword(s):  
Numerical Simulations ◽  
Shallow Water ◽  
Gravity Waves ◽  
Large Scale ◽  
Bottom Topography ◽  
Breaking Waves ◽  
Small Scale ◽  
Practical Consideration ◽  
Mean Flow ◽  
Vorticity Transport

Theoretical and numerical results are presented on the transport of vorticity (or potential vorticity) due to dissipating gravity waves in a shallow-water system with background rotation and bottom topography. The results are obtained under the assumption that the flow can be decomposed into small-scale gravity waves and a large-scale mean flow. The particle-following formalism of ‘generalized Lagrangian-mean’ theory is then used to derive an ‘effective mean force’ that captures the vorticity transport due to the dissipating waves. This can be achieved without neglecting other, non-dissipative, effects which is an important practical consideration. It is then shown that the effective mean force obeys the so-called ‘pseudomomentum rule’, i.e. the force is approximately equal to minus the local dissipation rate of the wave's pseudomomentum. However, it is also shown that this holds only if the underlying dissipation mechanism is momentum-conserving. This requirement has important implications for numerical simulations, and these are discussed.The novelty of the results presented here is that they have been derived within a uniform theoretical framework, that they are not restricted to small wave amplitude, ray-tracing or JWKB-type approximations, and that they also include wave dissipation by breaking, or shock formation. The theory is tested carefully against shock-capturing nonlinear numerical simulations, which includes the detailed study of a wavetrain subject to slowly varying bottom topography. The theory is also cross-checked in the appropriate asymptotic limit against recently formulated weakly nonlinear theories. In addition to the general finite-amplitude theory, detailed small-amplitude expressions for the main results are provided in which the explicit appearance of Lagrangian fields can be avoided. The motivation for this work stems partly from an on-going study of high-altitude breaking of internal gravity waves in the atmosphere, and some preliminary remarks on atmospheric applications and on three-dimensional stratified versions of these results are given.

scholarly journals Cyclic gravity waves in deep water

1983 ◽  
Vol 25 (1) ◽  
pp. 2-15 ◽  
Author(s):  
P. J. Bryant
Keyword(s):  
Wave Height ◽  
Gravity Waves ◽  
Deep Water ◽  
Fourier Transforms ◽  
Surface Displacement ◽  
Surface Boundary ◽  
Surface Boundary Conditions ◽  
Method Of Solution ◽  
Nonlinear Surface ◽  
The Waves

AbstractNumerical evidence is presented for the existence of unsteady periodic gravity waves of large height in deep water whose shape changes cyclically as they propagate. It is found that, for a given wavelength and maximum wave height, cyclic waves with a range of cyclic periods exist, with a steady wave of permanent shape being an extreme member of the range. The method of solution, using Fourier transforms of the nonlinear surface boundary conditions, determines the irrotational velocity field in the water and the water surface displacement as functions of space and time, from which properties of the waves are demonstrated. In particular, it is shown that cyclic waves are closer to the point of wave breaking than are steady permanent waves of the same wave height and wavelength.

scholarly journals Characteristics of Very Low Frequency Sound Propagation in Full Waveguides of Shallow Water

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 192
Author(s):  
Nansong Li ◽  
Hanhao Zhu ◽  
Xiaohan Wang ◽  
Rui Xiao ◽  
Yangyang Xue ◽  
...  
Keyword(s):  
Shallow Water ◽  
Wave Speed ◽  
Sound Propagation ◽  
Sea Water ◽  
Bottom Topography ◽  
Low Frequency ◽  
Acoustic Energy ◽  
Propagation Characteristics ◽  
Sea Bottom ◽  
Proposed Model

This work is concerned with the characteristics of very low frequency sound propagation (VLF, ≤100 Hz) in the shallow marine environment. Under these conditions, the classical hypothesis of considering the sea bottom as a fluid environment is no longer appropriate, and the sound propagation characteristics at the sea bottom should be also considered. Hence, based on the finite element method (FEM), and setting the sea bottom as an elastic medium, a proposed model which unifies the sea water and sea bottom is established, and the propagation characteristics in full waveguides of shallow water can be synchronously discussed. Using this model, the effects of the sea bottom topography and the various geoacoustic parameters on VLF sound propagation and its corresponding mechanisms are investigated through numerical examples and acoustic theory. The simulation results demonstrate the adaptability of the proposed model to complex shallow water waveguides and the accuracy of the calculated acoustic field. For the sea bottom topography, the greater the inclination angle of an up-sloping sea bottom, the stronger the leak of acoustic energy to the sea bottom, and the more rapid the attenuation of the acoustic energy in sea water. The effect of a down-sloping sea bottom on acoustic energy is the opposite. Moreover, the greater the pressure wave (P-wave) speed in the sea bottom, the more acoustic energy remains in the water rather than leaking into the bottom; the influence laws of the density and the shear wave (S-wave) speed in the sea bottom are opposite.

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