Showing papers on "Waves and shallow water published in 1977"

Polychaetes from intertidal areas in Panama, with a review of previous shallow-water records

Abstract: Fauchald, Kristian. Polychaetes from Intertidal Areas in Panama, with a Review of Previous Shallow-Water Records. Smithsonian Contributions to Zoology, number 221, 81 pages, 13 figures, 2 tables, 1977.—A total of 180 species are listed from both coasts of Panama. The material includes specimens collected by the Smithsonian Tropical Research Institute and specimens previously reported by Monro and Hartman in a series of papers. Newly described species are Aphrodita diplops, Eupanthalis perlae, Eunereis paitillae, Neanthes galetae, Neanthes pseudonoodti, Nereis panamensis, Marphysa amadae, Isolda bipinnata, and Euthelepus pascua. The eastern Pacific Ocean appears to be more species-rich than the western Atlantic, and relatively fewer species appear widespread in the Pacific than in the Atlantic Ocean. This fact may be because most of the sampling has been done on hard substrates in the Atlantic, while more diverse areas have been sampled in the Pacific. Generally, hard-substrate polychaetes are more widely dispersed than soft-bottom forms. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SEMES COVER DESICNThe coral Montastrea cavernosa (Linnaeus). Library of Congress Cataloging in Publication Data Fauchald, Kristian. Polychaetes from intertidal areas in Panama, with a review of previous shallow-water records. (Smithsonian contributions to zoology ; no. 221) Bibliography: p. Includes index. 1. Polychaeta—Panama. 2. Polychaeta—Pacific Ocean. I. Title. II. Series: Smithsonian Institution. Smithsonian contributions to zoology ; no. 221 QL1.S54 no. 221 [QL391.A6] 591.5 [595M47'097287] 76-6967

The effects of storms on the dynamics of shallow water benthic associations

Abstract: Muddy sands with dense benthic faunas occur patchily along the North Wales coast between tide swept grounds offshore and the wave washed sandy beaches. Although sheltered from prevailing winds the patches are intermittently disturbed by onshore gales. Monthly sampling in four localities with differing exposure over the 1975-76 winter allowed faunal changes to be compared with the relative wave energy of the storms. Wave scour washed out much of the fauna, sometimes causing mass stranding. Wave action also redistributed the fauna, thus playing a part in the formation of benthic associations as well as their destruction.

Behavior of Water in Vertical Well with Bottom Opening of Ship, and its Effects on Ship-Motion

Abstract: Recently some ships have been constructed with a vertical well which have the bottom opening for the purpose of raising and lowering the equipment. Some examples are vessel-type drilling rigs, vessels carrying small submersibles and so on.This paper shows the behavior of the water in the well, and its effects on the motion of the ship, when she is running.Experimental studies were performed under two different sets of conditions.(1) The motion of the free water surface in the well was studied, when the ship-model was fixed stationary in the stream.(2) The effect of the motion of the water in the well on the motion of the ship-model was studied, when the model was towed.The following conclusions were obtained.1) When the ship-model with a well is fixed stationary in the stream, it can be observed that the water surface moves regularly in it. This phenomenon is similar in many respects to the motion of a cylinder which is elastically supported by springs in the stream.2) The type of water motion, whether up and down, right and left or forwards and backwards, depends on the velocity of the stream and the shape of the well.3) The water motion can be seen at the dimensionless stream velocity of 0.2<2U/lω0<1.6, where U is the stream velocity, lis the length of the bottom opening and ω0 is the natural circular frequency of the water moving in the well.4) The experimental values agree well with the results of the theoretical calculation on the heaving amplitude of the free water surface in the well, and on the increased drag of the ship-model by the motion of water in it.5) In order to reduce the motion of water in the well, it is very effective to fix short flanges on its vertical walls a little below the water surface.

Rederivation of the Saturation Range in the Frequency Spectrum of Wind-Generated Gravity Waves

Abstract: The saturation range in the frequency spectrum of wind-generated waves is rederived. Laboratory and theoretical work show that wave breaking is the result of kinematic instability, suggesting that wave celerity is the governing parameter in the saturation range. Using similarity arguments, a general formulation is rederived giving the wave profile spectrum Sη(ω) ∝ ω−5 in deep water as derived by Phillips and Sη(ω) ∝ ω−3 in shallow water. The velocity spectrum in the saturation range is derived using linear wave theory as a spectral transfer function. In both deep and shallow water the horizontal velocity spectrum Su(ω) ∝ ω−3. Wave and velocity measurements made in deep and shallow water are presented showing agreement with theory.

A numerical experiment of the M 2 tide in the Yellow Sea.

Abstract: Semi-diurnal tides in the Yellow Sea are calculated by integrating the shallow water wave equations with frictional and inertial terms. It is found that the results depend on the bottom friction. In the frictionless case the tidal range is unstably amplified because of the occurrence of resonance of the semi-diurnal tidal component in Inchon Bay. When the bottom friction is in the form of the square of velocity, the results agree fairly well with the observations. The following results are obtained. First, the tidal range is larger at the coast of the Korean Peninsula than at the China Coast. Second, resonance of the semi-diurnal tide occurs in Inchon Bay. Third, bottom friction is very important in the shallow ocean,i.e., when the bottom friction become large, the phase lag is retarded and the tidal range decreases. The amplitude and the phase lag calculated in this study agree well with the observations in the case ofΤ b =γb 2 V¦V¦,γ b 2=0.0026, especially in the coast of the Korean Peninsula.

Diurnal fluctuations of temperature near the bottom of shallow water bodies as affected by solar radiation, bottom color and water circulation

Abstract: Measurements made in shallow lakes and tanks have shown that temperatures near and at the surface of substrates respond significantly to changes in solar radiation, water circulation and substrate color. Temperature differences between light and dark colored natural and artificial substrates ranged between 0.8 and 4.0 C°. Diurnal surface temperature ranges on a submerged black wooden disk varied 9C° when incoming solar radiation varied 14% or average daily windspeed changed from 0.9 to 3.6 ms−1. Fluctuations in substrate temperatures were poorly correlated with changes in nearby air or water temperatures.

Shallow Wave Diffraction around Large Cylinder

Abstract: The diffraction of cnoidal waves around a large vertical circular cylinder is investigated. First approximations are derived for the velocity potential of the flow field and consequently for the wave loading on the cylinder. The forces may be appreciably larger than predicted on the basis of shallow water sinusoidal wave theory, and the consequences on the design of large offshore structures in shallow water are assessed. The possibility of extending the theory to a second approximation is examined.

Shallow water macrobenthos along the central west coast of India

Abstract: Quantitative distribution of macrobenthos in five shallow bays of the central west coast of India was studied. The substrata in different bays largely consisted of sand and sand-mud. The fauna had a mean population density of 1279-5518/m2. It was rich below the low water mark up to 10 m, but progressively decreased with depth. A wide range of values of population density and biomass encountered suggested uneven distribution on similar deposits

A theory of non-linear waves in multi-dimensions: with special reference to surface water waves

Abstract: The surface water waves are "modal" waves in which the "physical space" (t, x, y, z) is the product of a propagation space (t, x, y) and a cross space, the z-axis in the vertical direction. We have derived a new set of equations for the long waves in shallow water in the propagation space. When the ratio of the amplitude of the disturbance to the depth of the water is small, these equations reduce to the equations derived by Whitham (1967) by the variational principle. Then we have derived a single equation in (t, x, y)-space which is a generalization of the fourth order Boussinesq equation for one-dimensional waves. In the neighbourhood of a wave froat, this equation reduces to the multidimensional generalization of the KdV equation derived by Shen & Keller (1973). We have also included a systematic discussion of the orders of the various non-dimensional parameters. This is followed by a presentation of a general theory of approximating a system of quasi-linear equations following one of the modes. When we apply this general method to the surface water wave equations in the propagation space, we get the Shen-Keller equation.

Mode conversion in shallow‐water sound propagation

Abstract: Coupled equations for modal power transfer are applied to calculate the energy transferred between normal modes as a result of scattering from the ocean floor. Numerical estimates are presented for mode conversion in a typical shallow‐water environment. The results show that mode coupling can have a significant effect on propagation loss. Mode‐coupling predictions obtained for farfield transmission loss are found to display both frequency‐ and range‐dependent features in qualitative agreement with observed shallow‐water transmission loss. Excellent agreement is obtained between mode‐coupling predictions and experimentally measured mode attenuation.

Contribution of the Second Order Terms to the Nonlinear Shallow Water Waves

Abstract: Contribution of the second order terms in the reductive perturbation theory has been investigated for the nonlinear shallow water waves. The fundamental equations are reduced to a coupled set of the Korteweg-de Vries equation for the first order horizontal velocity and a linear inhomogeneous equation for the second order arbitrary function. Structure of the coupled set of equations turns out to be the same as in the case of nonlinear ion acoustic wave. A steady state solution of the coupled set of equations has been examined in comparison with Laiton's analysis of the second order contribution of the Friedrich's expansion for the nonlinear shallow water waves.

A three-dimensional nonlinear model of tides

Abstract: It is of practical significance to investigate shallow water tides since there is a vast expanse of shallow sea surrounding our eastern border in the cast In this paper for the study of tidal waves in shallow water we present a three-dimentional nonlinear model On the basis of tidal constituent concept, the model designed could be used not only for the detection of astronomical tides but also for different orders of shallow water constituents For the jth order of constituents (as defined in the present article), the boundary value problems of elliptic differential equations for the tidal elevation are derived; in addition, the analytical expressions of the vertical distribution for tidal currents are deduced

The behaviour of a ship in restricted waters

Abstract: This paper deals with the problem of the behaviour of a ship in restricted waters with special regard to underkeel clearance. The main factors affecting the keel clearance are squat, heaving and pitching motions, the occurrence of a heeling angle due to wind pressure and rudder movements and the rolling motion. Distinction is made for canals, shallow water of finite width and shallow water of infinite width. It is emphasised that the efforts are mainly concentrated on the several calculation procedures which exist for squat and the difficulties involved in practical applications. With respect to the ship motions in shallow water waves a simple calculation method according to the conventional strip theory is presented and discussed.

The 1974 ALVIN Dives on Corner Rise and New England Seamounts.

Abstract: : Reconnaissance dives on seven of the New England Seamounts showed them to be rugged igneous features with pillow and massive basaltic rock exposures the dominent bottom type. A unique wall-like or radial dike was observed on two seamounts. Glacial erratics are rare on the east end of the chain but numerous on the west end. There are small bottom water currents that transport sediment sometimes causing sediment waves. There is a bottom biological population that distinctly varied from the eastern to the western seamounts. Mytilus was found to have a 300 meter shallow water coral cap rising above its volcanic base at 3,000 meters. None of the other seamounts visited on this cruise gave evidence of subsidence. (Author)

The shallow-water soft-bottom benthos in Lindåspollene, western Norway: 1. The study area and main sampling program

Abstract: As the local herring stock in Lindaspollene spawns in shallow water, and as the shallow-water area, constituting c. 15 % of the total Lindaspollene area, has a benthos different from the basins, a study of the shallow-water (less than 10 m) soft-bottom benthos in Lindaspollene was initiated. This paper, the first in a series, describes the study area, the main sampling program, and the environmental data obtained.

Nearshore Numerical Storm Surge and Tidal Simulation.

Abstract: : A two-dimensional, time-dependent, open-coast, long-wave, shallow-water model is presented. The model employs an orthogonal curvilinear coordinate system with telescoping computing cells. This permits greater resolution of the wave in the nearshore coastal region where principal interest is focused rather than at the continental shelf break or at far lateral distances from the region. The model treats the coastline as a finite height barrier which is broken with bay entrances. Coastal overtopping and bay communication with the open sea provide the means for the transport of water across the nominal coastline. Mass is conserved with all water lost from the ocean during the flood stage being stored in discrete bay ponding areas. Each ponding area is described by its particular storage area curve and its particular series of coastline computing grid segments. A prediction/correction method is employed for the computation of the coastal water level. The model has been employed in 11 verification studies. Included in the studies are simulations of storm surges from five hurricanes of record and astronomical tide and pseudosurge (transient large amplitude free wave) from two hydraulic physical models. Results from the simulations are presented. In all studies, the same barrier coefficients and procedure for determining the channel discharge coefficient were used. (Author)

Propagation of long waves over water of slowly varying depth

Abstract: SUMMARY Asymptotic expressions are obtained for the refraction, reflection and modulation of long waves progressing over water of variable depth when the rate of depth variation is small compared with the wavelength. The two- and three-dimensional cases are treated. in the case of long waves propagating down a canal, an analogous phenomenon occurs: the waves, in general, decompose into reflected and transmitted components each of which undergoes a modulation in amplitude, wave number and phase. An important problem for applications, as well as an interesting one mathematically, is to obtain explicit expressions for these phenomena when the depth varies in a general way. This problem, when formu- lated in terms of the exact linear theory of water waves, has proved difficult to solve, and, hence, researchers have relied on various approximate methods. The purpose of the present article is to present a method of solution which leads to ex- plicit asymptotic expressions for the refraction, reflection, and modulation of long waves when the rate of variation of the bottom elevation is small compared with the wavelength. In obtaining these results, the bottom surface is assumed to satisfy certain integrability and differentiability conditions but is otherwise unrestricted in shape. For the two-dimensional problem we find that the reflection coefficient diminishes as the smoothness of the bottom profile increases. The solution of the two-dimensional prob- lem remains valid when the rate of variation of the bottom elevation is of the order of magnitude of the wavelength, and, in fact, our reflection coefficient includes a result of Kreisel (2) for a non-slowly-varying bottom profile. In addition, we find that the phase shift, amplitude, and wave number depend not only on the bottom elevation but on all of the derivatives of the bottom elevation as well. As a result, our expression for the phase shift of the transmitted wave, in the case of no reflection, includes and extends the result obtained from the ray theory (described below) when the latter is applied to shallow water. For the three-dimensional problem we obtain an asymptotic expression, valid for small

Variability of Oceanographic Conditions at Ocean Weather Stations in the North Atlantic and North Pacific Oceans.

Abstract: : Seasonal mean salinity, temperature, and sound velocity and their variability were determined for 12 ocean weather stations. Variability above 200m depths is caused by wind-induced mixing and upwelling, advection and radiational heating and cooling. Below 200m internal waves and ocean fronts cause the variability. (Author)

Nonlinear Deep Water Waves: A Physical Testing Ground for Solitons and Recurrence

Abstract: The physical problem that we are concerned with is the evolution of nonlinear deep water waves. We shall assume that the waves under consideration are long enough so that the effect of surface tension is small compared to gravity (hence, they are sometimes referred to as “gravity waves”). This requires that the waves be much longer than 10 cm, at which wavelength surface tension and gravitational effects are comparable to each other. We shall assume that the water motion is incompressible, irrotational and inviscid. These are the usual approximations that go with the study of water waves, and are expected to be satisfied under normal circumstances. We shall also assume that the depth of the water is much larger than a typical wavelength. This deep water assumption is the opposite of the shallow water limit which leads to the well known Korteweg-de Vries equation-the first equation found to exhibit permanent, localized waveform solutions now known as solitons.

Slender-ship shallow-water flow past a slowly varying bottom

Abstract: The unsteady subcritical potential flow of a slender ship moving past a slowly varying bottom in shallow water is analyzed using the methods of matched asymptotic expansions and multiple scales. The hydrodynamic pressure field on the ship is obtained to second order in the slenderness parameter.