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As an introduction to this lecture, I think it will be appropriate to look into the variability of the meteorological parameters from year to year. This will quite clearly show the necessity of using data series of considerable length in order to obtain reliable probability statistics for meteorological parameters and oceanographic parameters which are chiefly governed by the wind conditions and/or sea level pressure.

Wave data recorded by a NOMAD buoy and a Waverider buoy in the west central basin of Lake Erie during September, October, and November 1984 are compared. Data include significant wave height, average wave period, wave spectra, and water temperature. The two systems were found to provide comparable estimates of wave height, wave period, and wave spectra only during periods when significant wave height exceeded 0.5 m. At lower wave heights, the NOMAD buoy gave slightly lower estimates of significant wave height than the Waverider. The Waverider processing system was unable to provide accurate spectral information for low wave heights because of aliasing. Water temperature measurements from the two systems were virtually identical.

An exact second-order theory is formulated for predicting the slowlyvarying second-order hydrodynamic forces on moored vessels in random waves. The near field approach based on direct integration of the fluid pressure on the submerged body surface is employed in conjunction with the Stokes expansion to second order. Green’s second identity is exploited to derive the expression for the second-order hydrodynamic forces due to the second-order velocity potential involving first-order quantities and the second-order undisturbed potential. It is shown that the contribution of the second-order potential to the slowly-varying forces may be significant in irregular seas with longer mean wave period.

In order to solve the two-dimensional long-wave equations numerically, the region of interest is covered by a rectangular grid. Recently, curvilinear grids that fit to the boundaries have been used but this is outside the scope of this book. There are various ways of arranging the variables in the grid, three of which are shown in Fig. 18.1.

A pipe-tire floating breakwater is currently being field tested in Presque Isle Bay, Erie, PA. Subassemblies of the breakwater were fabricated in three different configurations, two of which are being reported for the first time. Techniques are described for the launching and towing of the breakwater subassemblies to the mooring site using standard marina equipment. Final on-site assembly of the breakwater sections into an integral unit was facilitated by the positive buoyancy characteristics of the truck tire-cladded pipes which permitted personnel to move about on the structure. A field test site has been configured to obtain the wave transmission characteristics of the device and uses newly developed instrumentation for measuring, in real-time, the direction of wave advance, significant wave height and significant wave period parameters. Observations are reported on the behavior of the breakwater during the winter season.

The possibility of measuring erythrocyte flow velocity by means of grating laser microscope has been examined in an in vitro test using erythrocytes smeared on glass plates and in vivo using microvessels in the web of a frog foot. Magnified projections of flowing erythrocytes are spatially filtered by a simple glass plate grating and then detected by a photomultiplier. Output signals from the photomultiplier are first electronically filtered so as to yield oscillating burst-like wave signals. Moving erythrocytes resulted in burst-like oscillation in output signals whose wave period (T) changed with their velocities. These results suggest that the velocity (V) of erythrocytes could be given by V = d/MT, where d and M represent the grating constant and the optical magnification, respectively. The requirement for the establishment of this relation was examined by the microscopic observation of smeared erythrocyte preparation. It was shown that the flow velocity of erythrocyte could be measured even when the size of magnified images of erythrocytes strongly exceeded the value of d and even when many erythrocytes existed. A preliminary experiment to confirm the possibility of methodological adaptation was made by measuring the flow velocity in venules of foot web of frogs. Heart rate increased in all six frogs studied when the frog body was warmed. However, the peripheral flow velocity increased only in three frogs, while it remained almost unaffected in the other three. This result suggests that the frog peripheral microcirculation is affected by complicated intrinsic factors.

Publisher Summary This chapter discusses the development of beach profile. Changes in beach profiles constitute an important aspect of the erosion and accretion of near-shore coastal zones. Researchers have modeled beach and shoreline changes caused by oceanographic forces, such as winds, waves, currents, and man-made structures. Numerical models developed to describe coastal sediment transport are a simplified version of the transport mechanisms involved. Swart developed the basic equations for such a simplified model and verified his theory with laboratory and field data. The chapter presents the numerical basis of Swart's theory. It develops a numerical time-dependent cross-shore sediment transport model that calculates beach profile development. It also discusses the parameters used in the numerical model calculations: initial profile, wave height, wave period, diameter of testing material, and length of time of the test. The chapter concludes with a discussion of the method for calculating the equilibrium beach profile.

Wave data summaries for 1986 and summaries for all years from 1980 through 1986 are presented in this appendix. An explanation of the summary formats is followed by the data for Gages 625, 630, 640, and 645. Wave data are: (1) Gage Histories; (2) Daily H sub mo and T sub p; (3) Distributions of Wave Height Versus Peak Period; (4) Cumulative Distributions of Wave Height; (5) Peak Spectral Wave Period Distributions; (6) Persistence of Wave Heights; (7) Spectra.

Observations have been made of the occurrence of breaking waves at sea and their parameters to check the suitability of commonly used breaking wave criteria. Our analysis of the populations of breaking and non-breaking waves indicates that seemingly obvious parameters such as wave steepness or wave asymmetry cannot be used to distinguish between breaking waves and non-breaking waves.

A Type 949 Heave WAVE-TRACK Buoy and a Waverider 6000 Series Buoy were moored at approximately 7.0 miles west of the Columbia River entrance off Astoria, Oregon from December 19, 1979 to January 5, 1980 in approximately 200 feet depth. Wave statistics derived from a zero-upcrossing analysis and energy spectra are compared. Wave period measurements compared closely, while wave height measurements differed by less than 7.5% for significant wave heights ranging from 2.2-4.6 m (7.5-15.2 ft) and maximum wave heights exceeded 8.5 m (28 ft). Energy spectra for the WAVE-TRACK Buoy fell within the 90% confidence limits of the Waverider Buoy spectra.

The French wave prediction model DSA-5 is presented. The model uses the spectro-angular method to hindcast and forecast wave height, predominant wave direction, predominant wave period. Model tests in the Japan and East China Seas show close agreement between calculated and observed values although there is still a tendency for calculated values to overestimate observed ones especially in the case of weak wave heights. The most likely source of wave prediction errors seems to be strongly related to poor estimation of sea surface winds from weather charts.

This paper describes how two model basins, testing the same semisubmersible design, produced different motion response results. Subsequent testing revealed the phenomena that the heave response of the model is extremely sensitive to small changes in wave period. Calculations show that over- simplification of the heave response can produce significant overestimates of actual heave values, and, hence an overestimate of weather downtime that a drilling vessel will experience. It can be concluded that detailed model tests are very important for the accurate determination of vessel performance.

The preceding chapters may have conveyed the impression that we need refer only to unidirectional currents in order to give a physical account of sedimentary phenomena. We must emphasize that there is another important class of naturally occurring flows, characterized by rhythmical changes of speed combined with reversals of flow direction. These are the oscillatory currents associated with tides and with wind-generated surface waves. It is not immediately obvious that tides and wind waves belong in the same general class, but it turns out, as we shall see, that the tide can be analysed exactly as a type of wave. In addition to requiring some understanding of the origins of wind waves and tides, we shall in particular want to know what the currents due to them are like, what factors control these currents and the sediment transport they promote, and what bed- forms are adjusted to tidal and wave regimes. Some insight into these questions can be gained from simple experiments, from which it will become apparent that oscillatory flows can be much more complicated than unidirectional ones. But perhaps that is just part of their fascination.

The Model Sheltering Experiment deals with the planning arrangement of the proposed harbor and is done by the worst wave condition (with respect to wave direction, wave height, and wave period) which probably occurred on the proposed harbor. The objectives of this experiment are to get the wave pattern of the harbor basin and to understand the various phenomena of the wave refraction, diffraction, and reflection caused by model test due to different harbor arrangement, and to comprehend the sheltering effect of the outer breakwaters. From the analysis of these test results, harbor planning of the most effective arrangement – the most economic length of breakwaters and the most ideal width of harbor entrance could be selected. A comparison of theoretical wave diffraction calculation is proposed for the purpose of analyzing the results of model tests.

The light beacon which is installed on the sunken rock, etc.as navigation aid has great difficulty in securing power supply because of its installing location.

The wave data collected on board Ins Kistna from Bay of Bengal during July to August, 1964 and January, February and April, 1965 are presented. The wave parameters are analyzed and given in a form most suitable for model testing of ships. The variation of wave height with Beaufort number is remarkable. Wave periods from 2 to 10 seconds are observed with maximum frequency in the range of 2 to 5 seconds. The heights and period obtained are compared with those obtained by previous workers for the North Atlantic region and Bay of Bengal. The influence of the wave period 2 to 5 seconds on the rolling, pitching and heaving periods of medium size vessels is also discussed.

One result of the interaction of wind and ocean is the generation of surface waves. Prior to 1940 a few inadequate empirical rules formed the only basis for the prediction of wind-induced waves. A concentrated effort under the stimulus of wartime demands has resulted in the development of relationships which make possible the forecasting of ocean waves from synoptic meteorological data.

In this chapter, nonlinear effects are considered. These effects become more pronounced (1) when wave lengths are short compared with a characteristic length of the vessel (length when waves are head-on and beam when waves are beam-on), (2) when vessel is moored in shallow water so that draft/depth ratio is significant and (3) when natural period of mooring assembly is long relative to dominant wave period.

The shape sorting of pebbles in the swash zone was studied in an effort to determine the effect of the amount of foreshore infiltration per wave on the swash zone energy balance. Measurements were made of pebbles collected from the swash limit and from the step of selected sandy beaches. The pebbles were sampled on occasions when, and at locations where, the conditions of breaker height, breaker approach angle and foreshore slope fell within predetermined limits. The wave period and the foreshore infiltration rate varied among the beaches and were measured. The results of these measurements indicate that the mean shape of swash limit pebbles, and presumably, therefore, the swash zone energy balance depends upon the amount of foreshore infiltration per wave. This finding leads to the conclusion that in the study of the dynamics of the swash zone the effect of wave period and the effect of foreshore permeability must be considered together.

The following error appeared in column 2, page 232, in the paper by Joseph R. Curray, "Sediments and History of Holocene Transgression, Continental Shelf, Northwest Gulf of Mexico," in Recent Sediments, Northwest Gulf of Mexico, ed. F. P. Shepard et al., published by The American Association of Petroleum Geologists, 1960. The equation was printed: [EQUATION] where µ = horizontal component of orbital velocity at the bottom H = height of wave at the depth of water considered T = wave period in seconds h = depth of water L = wave length at the depth of water considered. The equation should read: [EQUATION] The symbol "sinh" represents the hyperbolic sine of the expression to follow rather than the sine of "h" times the expression to follow. End_of_Article - Last_Page 560

Two experiments were performed in an attempt to reproduce the correlations which Surwillo (1963a) found between reaction time (RT) and EEG wave period, using different experimental designs, stimulus modalities and period analysis paradigms. Surwillo analysed the EEG sample between the RT stimulus and response, which is likely to be complexly determined because of the contributions of the alpha blocking response and the evoked potential. In the first experiment a representative mean alpha period (from temporal and occipital derivations) was obtained for each of twelve subjects, using an automated, power spectrum based, period analysis system with which the EEG was sampled for about a minute. A non-significant inter-individual correlation of 0.37 was found between occipital alpha period and visual RT recorded under conditions of high incentive in a subsequent behavioral experiment. The finding was reproduced with an even lower correlation of 0.05 on another group of seventeen subjects. In the second experiment mean values of the EEG period were determined for twenty subjects from linear measurements on the chart of the 1 sec EEG sample immediately preceding each RT stimulus. The temporal derivation T 3 -T 5 was used during auditory RTs and the occipital derivation T 5 -O 1 during visual RTs. The interand mean intra-individual correlations between EEG period and RT were 0.21 and 0.10, respectively, for auditory RT and 0.26 and 0.10 for visual RT — statistically non-significant in each case. Thus there was a failure to reproduce the finding of Surwillo in both experiments, a discrepancy whose possible sources are discussed.

The observations on which this paper is based covered the period from January 1949 to December 1950. They included weekly measurements of the beach profile during part of the period at two selected points and were used to correlate beach changes with variations of wind force and direction, wave characteristics and other relevant data. The paper is presented in four parts: (i) Characteristics and location of the beach. (ii) Significant factors governing wave action in the locality and prevailing weather conditions. (iii) Analysis of the observations, with reference to relevant wave-tank experiments. (iii) Generally applicable results and conclusions.

Bridgmanite, the dominant mineral in the Earth’s lower mantle, crystallizes in the perovskite structure and transforms into post-perovskite at conditions relevant for the D$${}^{{\prime\prime} }$$″ layer. This transformation affects the dynamics of the Earth’s lowermost mantle and can explain a range of seismic observations. The thickness over which the two phases coexist, however, can extend over 100 km, casting doubt on the assignment of the observed seismic boundaries. Here, experiments show that the bridgmanite to post-perovskite transition in (Mg$${}_{0.86}$$0.86,Fe$${}_{0.14}$$0.14)SiO$${}_{3}$$3 is fast on geological timescales. The transformation kinetics, however, affects reflection coefficients of $$P$$P and $$S$$S waves by more than one order of magnitude. Thick layers of coexisting bridgmanite and post-perovskite can hence be detected using seismic reflections. Morever, the detection and wave period dependence of D$${}^{{\prime\prime} }$$″ reflections can be used to constrain significant features of the Earth’s lowermost mantle, such as the thickness of the coexistence layer, and obtain information on temperature and grain sizes.

This paper describes the operational wave forecasting system that has been implemented at the Portuguese Institute for Ocean and Atmosphere (IPMA) along the west coast of the Iberian Peninsula. This system is based on the Simulating WAves Nearshore (SWAN) model, is forced at the boundaries by the Limited-Area Wave (LAW) model forecasts generated by the European Centre for Medium-Range Weather Forecasts (ECMWF) and by the 10m wind fields from the ALADIN atmospheric model. Moreover, the performance of three SWAN whitecapping parameterisations is evaluated. This evaluation is performed for significant wave height, mean wave period and mean wave direction forecasts through comparisons with observations from four buoys over a six month period. Finally, it gives a short evaluation of the operational version of SWAN model at IPMA during the recent Christina Storm.

Crystals A2BX4 become of great interest for investigators because they have an incommensurate phase in a certain temperature range. Since modulation wave period is still much shorter than wavelength of the visible light, there is opinion that macroscopic methods (such as method of investigating birefringence and electrooptical properties) are not sensitive to the phase transition of paraelectric—incommensurate (Ti) and incommensurate—commensurate (T0) phases types.

This paper describes the effect of wave period on the stability of rubble mound breakwaters. Introductorily wave run-up and run-down on smooth slopes and on rubble mounds were measured, and breaker types were observed and recorded for different incoming wave and slope characteristics. The surf similarity parameter, 5 = , 9° = /-~ • ~^r ' T was found practical for /H/L0 / 2TT /H description of breaker type, run-up and run-down on both smooth and permeable slopes. Pressure measurements along the smooth slopes and in the core of a rubble mound were undertaken with two different core materials. It was shown that the most dangerous condition for the stability of rubble mounds occurs at the so-called "resonance condition". Resonance refers to the situation that occurs when run-down is in a low position and collapsing- plunging wave breaking takes place simultaneously and repeatedly at or close to that location. This corresponds to a range of E, values in between 2 and 3. Photographic instrumentation was introduced and tested to quantify the initial damage on a rubble mound. This paper is a 1/3 abstact of a thesis for the Dr. Eng. degree by Ali Riza Giinbak.

The Model Sheltering Experiment deals with the planning arrangement of the proposed harbor and is done by the worst wave condition (with respect to wave direction, wave height, and wave period) which probably occurred on the proposed harbor. The objectives of this experiment are to get the wave pattern of the harbor basin and to understand the various phenomena of the wave refraction, diffraction, and reflection caused by model test due to different harbor arrangement, and to comprehend the sheltering effect of the outer breakwaters. From the analysis of these test results, harbor planning of the most effective arrangement - the most economic length of breakwaters and the most ideal width of harbor entrance could be selected. For the purpose of analyzing results of model tests; comparison of theoretical wave diffraction calculation is proposed.

It is proposed that the singularity of each beach setting results in longshore current developments unique to the location and conditions. Therefore it is plausible that the inter-relationships between the longshore current variables are not constant. This is in spite of the similarity of results in past studies that suggest a general form for longshore current regression solutions and current mathematical refinements of equations. Herein contemporaneous empirical studies of two dissimilar nearshore environments along Sandy Hook, New Jersey suggest different reactions to the same wave train. Regression models with coefficients of determination exceeding 60 %/o reveal that wave period, nearshore slope, and the angle of wave approach are important on low energy beaches while breaker height is the primary control on longshore current velocities for higher energy beaches.

A wave recorder has been in operation at Camp Pendleton, Oceanside, California, since May 4, 1949. Owing to its fortunate location in relation to the Western Hemisphere's hydrography, it has recorded southerly swell almost continuously throughout the summer, the origins of which appear to lie in the area between 40° and 65°S and 120° and 160°W. Swell from the south through southwest was found to run almost continuously from May through September, and to dominate the surf zone for that period. Twenty- to thirty-minute averages (taken three times daily) of the “significant” breaker heights ranged from two to six feet, with most breakers.being between two and four feet. The “maximum” breakers occurring during the 20- to 30-min periods were usually between four and eight feet, with heights of 10 to 12 ft observed on occasions. The average wave period of the southern swell ranged from 12 to 18 sec, with short-time averages of predominant groups as great as 22 sec.

Under the discussion of wave period, the author states, “Periods of surface waves are to be expected to be lower than those recorded at or near the bottom.” This statement is true, but it should be supplemented by a statement to the effect that, by placing a pressure pick-up unit below the sea surface, pressure fluctuations due to the shorter period waves are inappreciable or non-existent because of hydro-dynamic filtering. Thus, only the pressure fluctuations from the longer period waves are present to activate an underwater pressure pick-up unit. The relationships between the period of subsurface pressure-fluctuations and the average period of the combined wind waves and swell observed at the surface given by the author for stations at Cuttyhunk and Bermuda were merely a function of the depth of the instruments and the wind waves and swell that existed at the time of the observations. With different depths of instrument and different wave conditions, the filtering effects would be different; hence the ratio of periods as observed at the surface and recorded by an underwater instrument would be different. Without explanatory supplementary statements on filtering action accompanying wave motion, it is believed that the casual reader would be led to the erroneous belief that a certain single wave train would have a different period whether observed at the surface or below the surface.

An expression is derived from very general assumptions for the increase in wave period during long-distance propagation. To illustrate the general nature of the solution, application is made to three different geophysical phenomena: First, to the tsunami from the Aleutian earthquake of April 1, 1946; second, to the long forerunners of the swell recorded at the wave station in Pendeen, England; and finally to the seismic surface waves from the Montana earthquake of June 28, 1925, and a smaller Mexican shock in 1943. In the case of the tsunami and the swell, observations and theory are in good agreement. For the seismic surface waves the theory gives at least the right order of magnitude. Application of the theory to the period increase of swell seems furthermore to provide a simple, rational basis for locating and tracking storms at sea by means of swell observations, and may therefore be of interest in weather forecasting.

Data obtained from two surface profile wave gages and two pressure wave gages at the Steel Pier in Atlantic City, New Jersey, are used to check the consistency of the analysis variables obtained from a given set of records by several commonly used analysis procedures All estimates of the characteristic height tested are found to be correlated better than 86 The estimates of characteristic period are not so satisfactory and in some cases are below 25 Consideration of several proposed definitions of the characteristic period indicates that they are based more on convenience in data processing than on application of the derived data Consideration of the use of wave data in engineering design shows that no one definition of the period can be satisfactory for all applications The best definition of the characteristic wave period for a given engineering problem can be specified only when the dynamic aspects of the problem have been identified.