scholarly journals REFRACTION OF FINITE-HEIGHT AND BREAKING WAVES

1976 ◽  
Vol 1 (15) ◽  
pp. 28 ◽  
Author(s):  
James R. Walker
Keyword(s):  
Three Dimensional ◽  
Wave Theory ◽  
Breaking Waves ◽  
Finite Amplitude ◽  
Primary Objective ◽  
Test Series ◽  
Data Sets ◽  
Linear Wave ◽  
Wave Refraction ◽  
Wave Shoaling

The primary objective of this study was to ascertain the influence of wave height and breaking on wave refraction over a three-dimensional shoal. The subject wave transformations were studied in an hydraulic model. Wave shoaling, decay in the breaker zone, and phase velocities were analyzed in a base test series over a bottom slope of 1:30. A second test series was conducted over a three-dimensional shoal. Wave patterns were photographed and wave heights and celerities were measured. The measurements were compared with wave refraction patterns and coefficients computed by analytical methods. Wave shoaling observed over the constant 1:30 slope was 25 percent greater than predicted by Airy theory at the breaking point for wave steepness H0/L0=.030 and 50 percent greater than predicted for H0/Lo = •002. Shoaling measurements were compared with other empirical data sets, confirming the inadequacy of commonly used practice using linear wave theory near the breaker zone. The celerity measurements indicated that the non-breaking celerity was given by C = (1+.25 H/d)Ca, where Ca is the Airy celerity. The discussion and results give a basic understanding of wave refraction near the breaker zone, supplementing analytical papers on refraction procedures using finite amplitude wave theories.

scholarly journals POLYNOMIAL APPROXIMATION AND WATER WAVES

1986 ◽  
Vol 1 (20) ◽  
pp. 15 ◽  
Author(s):  
John D. Fenton
Keyword(s):  
Polynomial Approximation ◽  
Water Waves ◽  
Three Dimensional ◽  
Wave Theory ◽  
General Nature ◽  
Linear Wave ◽  
Wave Refraction ◽  
Approximate Wave ◽  
Spatial Approximation ◽  
Wave Problems

A different approach to the solution of water wave problems is considered. Instead of using an approximate wave theory combined with highly accurate global spatial approximation methods, as for example in many applications of linear wave theory, a method is developed which uses local polynomial approximation combined with the full nonlinear equations. The method is applied to the problem of inferring wave properties from the record of a pressure transducer, and is found to be capable of high accuracy for waves which are not too short, even for large amplitude waves. The general approach of polynomial approximation is well suited to problems of a rather more general nature, especially where the geometry is at all complicated. It may prove useful in other areas, such as the nonlinear interaction of long waves, shoaling of waves, and in three dimensional problems, such as nonlinear wave refraction and diffraction.

scholarly journals The production of waves by the sudden release of a spherical distribution of compressed air in the atmosphere

1941 ◽  
Vol 178 (973) ◽  
pp. 153-170 ◽  
Keyword(s):  
Shock Wave ◽  
Sound Wave ◽  
Complete Solution ◽  
Spherical Wave ◽  
Three Dimensional ◽  
Wave Theory ◽  
Initial Distribution ◽  
Finite Amplitude ◽  
Compressed Air ◽  
Compressible Medium

An attempt has been made to develop a method for dealing with solutions of problems connected with the production of waves by spherical concentrations of compressed air. Starting from the general equations for three-dimensional spherically symmetrical flow in a homogeneous compressible medium having constant entropy everywhere, a process has been devised to apply step-by-step calculations over small intervals of time to investigate the general features of such a motion. A complete solution has been worked out in one particular case for a not very intense initial distribution of pressure, and various indirect checks have indicated that the results are reasonably accurate. These results show m any features of definite interest. As distinct from plane or spherical sound wave theory, it is found that a train of waves passes away from the centre of disturbance, the amplitudes and wave lengths falling off from wave to wave. Furthermore, as distinct from finite amplitude plane wave theory which shows that any wave must eventually become a shock wave, the waves obtained in the finite amplitude spherical wave case show no indication of becoming shock waves, and indeed show towards the closing stages of the calculation a similarity to sound wave propagation. The method is applicable to any spherically symmetrical motion up to such a time as the formation of a shock wave takes place and then fails owing to the assumption of constant entropy.

scholarly journals Three Dimensional Radiated Water Wave with a Submerged Cylinder in Presence of Circular Plate

2019 ◽  
Vol 9 (1) ◽  
pp. 6665-6670
Keyword(s):  
Separation Of Variables ◽  
Surface Condition ◽  
Three Dimensional ◽  
Wave Interaction ◽  
Wave Theory ◽  
Linear Wave ◽  
Energy Device ◽  
Linear Wave Theory ◽  
Bernoulli’S Equation ◽  
Submerged Cylinder

This work deals with the problem of radiated by wave interaction with a couple of submerged cylinders in water which can be considered as a wave energy device and the problem arising from the rotational motion of submerged upper cylinder which one contains in the device. In this work, we approach theoretically to solve the problem based on the method of separation of variables and we derive the radiated velocity potentials numerically based on linear wave theory and eigenfunctions are introduced for each region by using free surface condition. Then we calculate the hydrodynamic coefficients due to rotational of the upper cylinder by using Bernoulli’s equation of pressure by neglecting the atmospheric pressure and unknown constants are calculate by using matched conditions between the regions Finally, we present all numerical results graphically for different radii of the cylinders

scholarly journals TRANSMISSION OF REGULAR WAVES PAST FLOATING PLATES

1974 ◽  
Vol 1 (14) ◽  
pp. 112
Author(s):  
Uygur Sendil ◽  
W.H. Graf
Keyword(s):  
Water Depth ◽  
Wave Length ◽  
Wave Theory ◽  
Finite Amplitude ◽  
Linear Wave ◽  
Regular Waves ◽  
Transmission Coefficients ◽  
Wave Flume ◽  
Wave Heights ◽  
Incident Waves

Theoretical solutions for the transmission beyond and reflection of waves from fixed and floating plates are based upon linear wave theory, as put forth by John (1949), and Stoker (1957), according to which the flow is irrotational, the fluid is incompressible and frictionless, and the waves are of small amplitude. The resulting theoretical relations are rather complicated, and furthermore, it is assumed that the water depth is very small in comparison to the wave length. Wave transmissions beyond floating horizontal plates are studied in a laboratory wave flume. Regular (harmonic) waves of different heights and periods are generated. The experiments are carried out over a range of wave heights from 0.21 to 8.17 cm (0.007 to 0.268 ft), and wave periods from 0.60 to 4.00 seconds in water depth of 15.2, 30.5, and 45.7 cm (0.5, 1.0 and 1.5 ft). Floating plates of 61, 91 and 122 cm (2, 3 and 4 ft) long were used. From the analyses of regular waves it was found that: (1) the transmission coefficients, H /H , obtained from the experiments are usually less than those obtained from the theory. This is due to the energy dissipation by the plate, which is not considered in the theory. (2) John's (1949) theory predicts the transmission coefficients, H /H , reasonably well for a floating plywood plate, moored to the bottom and under the action of non-breaking incident waves of finite amplitude. (3) a floating plate is less effective in damping the incident waves than a fixed plate of the same length.

scholarly journals COUPLING STOKES AND CNOIDAL WAVE THEORIES IN A NONLINEAR REFRACTION MODEL

1988 ◽  
Vol 1 (21) ◽  
pp. 42
Author(s):  
Thomas A. Hardy ◽  
Nicholas C. Kraus
Keyword(s):  
Nonlinear Refraction ◽  
Wave Model ◽  
Wave Theory ◽  
Quantitative Agreement ◽  
Wave Mode ◽  
Finite Amplitude ◽  
Second Order ◽  
Stokes Wave ◽  
Linear Wave ◽  
Cnoidal Wave

An efficient numerical model is presented for calculating the refraction and shoaling of finite-amplitude waves over an irregular sea bottom. The model uses third-order Stokes wave theory in relatively deep water and second-order cnoidal wave theory in relatively shallow water. It can also be run using combinations of lower-order wave theories, including a pure linear wave mode. The problem of the connection of Stokes and cnoidal theories is investigated, and it is found that the use of second-order rather than first-order cnoidal theory greatly reduces the connection discontinuity. Calculations are compared with physical model measurements of the height and direction of waves passing over an elliptical shoal. The finite-amplitude wave model gives better qualitative and quantitative agreement with the measurements than the linear model.

scholarly journals NEW FRAMEWORK FOR PREDICTION OF LONGSHORE CURRENTS

1982 ◽  
Vol 1 (18) ◽  
pp. 99 ◽  
Author(s):  
C.A. Fleming ◽  
D.H. Swart
Keyword(s):  
Wave Theory ◽  
Data Sets ◽  
Linear Wave ◽  
Random Waves ◽  
Longshore Currents ◽  
Longshore Sediment Transport ◽  
Longshore Transport ◽  
Bed Roughness ◽  
Accuracy Of Prediction ◽  
New Framework

The accuracy of prediction of longshore sediment transport depends largely on the accuracy with which the wave-driven longshore currents within the breaker zone can be predicted. Longuet-Higgins (1970) developed a formulation for longshore transport which is widely used today. In the present paper the basic theory of Longuet-Higgins is reexamined. The effect of bed roughness on the magnitude of the longshore current is quantified with the aid of over 350 individual data sets and the theory is theoretically extended to include the effect of random waves, in a similar way to Battjes (1974), and higher-order waves. For this latter purpose the Vocoidal water wave theory of Swart (1978) is used. It is shown that the use of Vocoidal theory leads to a velocity distribution which is in closer correspondence to measured data than that predicted by using linear wave theory.

scholarly journals Bathymetric Inversion and Uncertainty Estimation from Synthetic Surf-Zone Imagery with Machine Learning

2020 ◽  
Vol 12 (20) ◽  
pp. 3364
Author(s):  
Adam Collins ◽  
Katherine Brodie ◽  
Andrew Spicer Bak ◽  
Tyler Hesser ◽  
Matthew Farthing ◽  
...  
Keyword(s):  
Surf Zone ◽  
Mean Squared Error ◽  
Numerical Models ◽  
Wave Theory ◽  
Complete Information ◽  
Breaking Wave ◽  
Linear Wave ◽  
Wave Refraction ◽  
Additional Information ◽  
Single Frame

Resolving surf-zone bathymetry from high-resolution imagery typically involves measuring wave speeds and performing a physics-based inversion process using linear wave theory, or data assimilation techniques which combine multiple remotely sensed parameters with numerical models. In this work, we explored what types of coastal imagery can be best utilized in a 2-dimensional fully convolutional neural network to directly estimate nearshore bathymetry from optical expressions of wave kinematics. Specifically, we explored utilizing time-averaged images (timex) of the surf-zone, which can be used as a proxy for wave dissipation, as well as including a single-frame image input, which has visible patterns of wave refraction and instantaneous expressions of wave breaking. Our results show both types of imagery can be used to estimate nearshore bathymetry. However, the single-frame imagery provides more complete information across the domain, decreasing the error over the test set by approximately 10% relative to using timex imagery alone. A network incorporating both inputs had the best performance, with an overall root-mean-squared-error of 0.39 m. Activation maps demonstrate the additional information provided by the single-frame imagery in non-breaking wave areas which aid in prediction. Uncertainty in model predictions is explored through three techniques (Monte Carlo (MC) dropout, infer-transformation, and infer-noise) to provide additional actionable information about the spatial reliability of each bathymetric prediction.

scholarly journals THE INTERACTION OF SMALL AND FINITE AMPLITUDE LONG WAVES AND CURRENTS

1984 ◽  
Vol 1 (19) ◽  
pp. 67 ◽  
Author(s):  
F. Raichlen ◽  
J.J. Lee
Keyword(s):  
Power Plants ◽  
Cooling Water ◽  
Breaking Waves ◽  
Finite Amplitude ◽  
Offshore Structure ◽  
Wave Refraction ◽  
Steady Current ◽  
Waves And Currents ◽  
The Waves ◽  
A Current

The interaction of waves and currents is important for many engineering problems. For example, when considering forces on marine structures, the velocity and acceleration field must be defined, and thus the manner in which a current interacts with small and finite amplitude waves must be understood. When the current is large and oblique to the waves, the direction of the force on an offshore structure may change significantly with depth introducing a torsional moment. Wave refraction and the concomitant attenuation or amplification of waves are also affected by offshore currents. An example is the effect on incident waves of offshore currents induced by the discharge of cooling water from coastal-sited power plants. This current can modify the direction and magnitude of approaching waves, and by these changes the breaking waves at the shore and the nearshore sediment transport associated with these waves may be changed. A number of theoretical studies have been conducted on various aspects of wave-current interactions; see Peregrine (1976). One theoretical study, Thomas (1981), will be used in this investigation. Careful experiments in this area are limited; several are: Iwagaki and Asano (1980), Sarpkaya (1957), and Thomas (1981). Each of these has given attention to certain aspects of small amplitude wave-current interactions. The experiments are difficult to conduct because of the problems inherent in introducing waves into a flume with a steadyuniform current or conversely a current into a wave tank with permanent waves. Certain features of these experimental problems can be seen through the following two examples. If a plunger-wave machine were used and located at one end of a flume in which a steady current is flowing, although the waves would be developing as they interact with the current, the previously steady current would be changed to an unsteady one by the periodic blockage of the flow by the plunger. If the waves are generated at one end of the tank and allowed to develop, and a current is introduced from the bottom of the tank, this current must expand to the full depth of the flow; hence, the waves propagate on a developing current. Therefore, comparisons to theory are, to some extent, difficult to realize, because the theory generally assumes wavecurrent interactions when each is fully developed.

scholarly journals Study of a TLP motions and forces using 3D source technique

2019 ◽  
Vol 16 (2) ◽  
pp. 77-86
Author(s):  
M R Islam ◽  
M M Rahaman ◽  
A Kumar
Keyword(s):  
Deep Sea ◽  
Degrees Of Freedom ◽  
Oil And Gas ◽  
Three Dimensional ◽  
Wave Theory ◽  
Petroleum Products ◽  
Frequency Domain Analysis ◽  
Source Distribution ◽  
Linear Wave ◽  
Linear Wave Theory

The production and consumption of oil and other petroleum products have been increasing rapidly over the years, which led to the scarcity of easily retrieved oil due to urbanization. As a result, oil producers are motivated to go to deeper ocean to extract oil and other resources.Offshore platforms in deep water like TLPs are used for exploration of oil and gas from under Seabed and processing. But it is challenging to design precisely such type of giant structure in deep sea as it experiences huge forces, motion and other environmental loads which are non-linear, need sophisticated solution techniques and expensive to apply. In the present study wave exciting forces and motions of free floating TLP are carried out in frequency domain analysis using three dimensional source distribution techniques within the scope of linear wave theory where six degrees of freedom have been considered. The same geometrical data are used as an input to HydroStar, which is based on linear wave theory. Results obtained from both the programs are compared which shows a good agreement and also validated with the published results. Comparison of heave motion with and without tether are illustrated where it can be easily understood the effect of tendon. Forces and motions prediction of TLP is emphasized which has been done precisely in the present work and in future it will help us to design the TLPs as well as the tendon system in deep sea. Finally, a number of recommendations have been made for further research based on the present study.

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