Longshore variations in longshore currents

1977 ◽  
Vol 14 (8) ◽  
pp. 1897-1905 ◽  
Author(s):  
J. R. Keeley ◽  
A. J. Bowen
Keyword(s):  
Wave Height ◽  
Large Scale ◽  
Surf Zone ◽  
Small Scale ◽  
Angle Of Incidence ◽  
Wave Direction ◽  
Incoming Wave ◽  
Wave Refraction ◽  
Longshore Currents ◽  
Deep Water Wave

The mean longshore currents in the surf zone were measured along more than 1 km of a beach. These measurements were compared to a theoretical model of the system in which the current depends on the angle of incidence of the incoming waves and the longshore variation in both wave height and breaker angle. A wave refraction programme was used to compute the values of wave height and breaker angle every 100 m along the beach from the measured values of wave period and deep water wave direction. In general, the large scale variation of currents along the beach was well described by the theory. However, superimposed upon these large scales of motion were fairly regular, small-scale circulation cells which are probably associated with edge waves at the incoming wave frequency.

The Concept of the Optimum Alignment of Discharge Pipelines Due to the Minimization of the Wave Forces

1992 ◽  
Vol 25 (9) ◽  
pp. 211-216
Author(s):  
A. Akyarli ◽  
Y. Arisoy
Keyword(s):  
Wave Height ◽  
Wave Force ◽  
Wave Forces ◽  
Wave Direction ◽  
Incoming Wave ◽  
Pipeline Route ◽  
Optimum Alignment ◽  
The Cost ◽  
Resultant Wave

As the wave forces are the function of the wave height, period and the angle between the incoming wave direction and the axis of the discharge pipeline, the resultant wave force is directly related to the alignment of the pipeline. In this paper, a method is explained to determine an optimum pipeline route for which the resultant wave force becomes minimum and hence, the cost of the constructive measures may decrease. Also, the application of this method is submitted through a case study.

scholarly journals Environmental controls on surf zone injuries on high-energy beaches

2019 ◽  
Vol 19 (10) ◽  
pp. 2183-2205 ◽  
Author(s):  
Bruno Castelle ◽  
Tim Scott ◽  
Rob Brander ◽  
Jak McCarroll ◽  
Arthur Robinet ◽  
...  
Keyword(s):  
Wave Height ◽  
Surf Zone ◽  
High Tide ◽  
High Energy ◽  
Water Levels ◽  
Small Scale ◽  
Beach Morphology ◽  
Environmental Controls ◽  
Flow Activity ◽  
Incident Waves

Abstract. The two primary causes of surf zone injuries (SZIs) worldwide, including fatal drowning and severe spinal injuries, are rip currents (rips) and shore-break waves. SZIs also result from surfing and bodyboarding activity. In this paper we address the primary environmental controls on SZIs along the high-energy meso–macro-tidal surf beach coast of southwestern France. A total of 2523 SZIs recorded by lifeguards over 186 sample days during the summers of 2007, 2009 and 2015 were combined with measured and/or hindcast weather, wave, tide, and beach morphology data. All SZIs occurred disproportionately on warm sunny days with low wind, likely because of increased beachgoer numbers and hazard exposure. Relationships were strongest for shore-break- and rip-related SZIs and weakest for surfing-related SZIs, the latter being also unaffected by tidal stage or range. Therefore, the analysis focused on bathers. More shore-break-related SZIs occur during shore-normal incident waves with average to below-average wave height (significant wave height, Hs = 0.75–1.5 m) and around higher water levels and large tide ranges when waves break on the steepest section of the beach. In contrast, more rip-related drownings occur near neap low tide, coinciding with maximised channel rip flow activity, under shore-normal incident waves with Hs >1.25 m and mean wave periods longer than 5 s. Additional drowning incidents occurred at spring high tide, presumably due to small-scale swash rips. The composite wave and tide parameters proposed by Scott et al. (2014) are key controlling factors determining SZI occurrence, although the risk ranges are not necessarily transferable to all sites. Summer beach and surf zone morphology is interannually highly variable, which is critical to SZI patterns. The upper beach slope can vary from 0.06 to 0.18 between summers, resulting in low and high shore-break-related SZIs, respectively. Summers with coast-wide highly (weakly) developed rip channels also result in widespread (scarce) rip-related drowning incidents. With life risk defined in terms of the number of people exposed to life threatening hazards at a beach, the ability of morphodynamic models to simulate primary beach morphology characteristics a few weeks or months in advance is therefore of paramount importance for predicting the primary surf zone life risks along this coast.

scholarly journals Environmental controls on surf zone injuries on high-energy beaches

2019 ◽  
Author(s):  
Bruno Castelle ◽  
Tim Scott ◽  
Rob Brander ◽  
Jak McCarroll ◽  
Arthur Robinet ◽  
...  
Keyword(s):  
Wave Height ◽  
Surf Zone ◽  
High Tide ◽  
High Energy ◽  
Water Levels ◽  
Small Scale ◽  
Beach Morphology ◽  
Environmental Controls ◽  
Flow Activity ◽  
Incident Waves

Abstract. The two primary causes of surf zone injuries (SZIs) worldwide, including fatal drowning and severe spinal injuries, are rip currents (rips) and shore-break waves. SZIs also result from surfing and body boarding activity. In this paper we address the primary environmental controls on SZIs along the high-energy meso-macrotidal surf beach coast of SW France. A total of 2523 SZIs recorded by lifeguards over 186 sample days during the summers of 2007, 2009 and 2015 were combined with measured and/or hindcast weather, wave, tide and beach morphology data. All SZIs occurred disproportionately on warm sunny days with low wind likely because of increased beachgoer numbers and hazard exposure. Relationships were strongest for shore break and rip related SZIs and weakest for surfing related SZIs, the latter being also unaffected by tidal stage or range. Therefore the analysis focussed on bathers. Shore-break related SZIs disproportionately occur during shore-normal incident waves with average to below-average wave height (significant wave height Hs = 0.75–1.5 m) and around higher water levels and large tide range when waves break on the steepest section of the beach. In contrast, rip related drownings occur disproportionally near neap low tide, coinciding with maximized channel rip flow activity, under shore-normal incident waves with Hs > 1.25 m and periods mean wave period longer than 5 s. Additional drowning incidents occurred at spring high tide, presumably due to small-scale swash rips. The composite wave and tide parameters proposed by Scott et al. (2014) are key controlling factors determining SZI occurrence, although the risk ranges are not necessarily transferable to all sites. Summer beach and surf zone morphology is highly interannually variable, which is critical to SZI patterns. The upper beach slope can vary from 0.06 to 0.18 between summers, resulting in low and high shore-break related SZIs, respectively. Summers with coast-wide highly (weakly) developed rip channels also result in widespread (scarce) rip related drowning incidents. With life risk defined in terms of the number of people exposed to life threatening hazards at a beach, the ability of morphodynamic models to simulate primary beach morphology characteristics a few weeks/months in advance is therefore of paramount importance to predict the primary surf-zone life risks along this coast.

Interaction of a deep-water wave with a vertical cylinder: effect of self-excited vibrations on quantitative flow patterns

2007 ◽  
Vol 572 ◽  
pp. 189-217 ◽  
Author(s):  
M. OZGOREN ◽  
D. ROCKWELL
Keyword(s):  
Flow Structure ◽  
Deep Water ◽  
Water Wave ◽  
Large Scale ◽  
Wave Motion ◽  
Vertical Cylinder ◽  
Small Scale ◽  
Cylinder Surface ◽  
Deep Water Wave ◽  
Quantitative Flow

Interaction of a deep-water wave with a cylinder gives rise to ordered patterns of the flow structure, which are quantitatively characterized using a technique of high-image-density particle image velocimetry. When the cylinder is stationary, the patterns of instantaneous flow structure take on increasingly complex forms for increasing Keulegan--Carpenter number KC. These patterns involve stacking of small-scale vorticity concentrations, as well as large-scale vortex shedding. The time-averaged consequence of these patterns involves, at sufficiently high KC, an array of vorticity concentrations about the cylinder.When the lightly damped cylinder is allowed to undergo bidirectional oscillations, the trajectories can be classified according to ranges of KC. At low values of KC, the trajectory is elliptical, and further increases of KC allow, first of all, both elliptical and in-line trajectories as possibilities, followed by predominantly in-line and figure-of-eight oscillations at the largest value of KC.Representations of the quantitative flow structure, in relation to the instantaneous cylinder position on its oscillation trajectory, show basic classes of patterns. When the trajectory is elliptical, layers of vorticity rotate about the cylinder surface, in accordance with rotation of the relative velocity vector of the wave motion with respect to the oscillating cylinder. Simultaneously, the patterns of streamline topology take the form of large-scale bubbles, which also rotate about the cylinder. When the cylinder trajectory is predominantly in-line with the wave motion, generic classes of vortex formation and shedding can be identified; they include sweeping of previously shed vorticity concentrations past the cylinder to the opposite side. Certain of these patterns are directly analogous to those from the stationary cylinder.

scholarly journals IRREGULAR WAVE TRANSFORMATION AFFECTED BY OPPOSING CURRENTS

1986 ◽  
Vol 1 (20) ◽  
pp. 53
Author(s):  
Shigeki Sakai ◽  
Kouestu Hiyamizu ◽  
Hiroshi Saeki
Keyword(s):  
Wave Height ◽  
Present Model ◽  
Surf Zone ◽  
Transformation Model ◽  
Irregular Waves ◽  
Wave Transformation ◽  
Irregular Wave ◽  
Sea Bed ◽  
Dimensionless Unit ◽  
Deep Water Wave

Transformation of irregular waves affected by opposing currents on a sloping sea bed was discussed, experimentally and theoretically. It was found that representative values of wave height, such as a significant wave height, are larger before breaking and the wave height decaying occurs more promptly in a surf zone as opposing currents become dominant, and that characteristics of a irregular wave transformation are determined by the dimensionless unit width discharge q* and the deep water wave steepness. This means that the effects of opposing currents on irregular wave transformation are qualitatively identical to that on the regular waves. A transformation model of irregular waves affected by opposing currents was presented. In the model, formulations for a regular wave transformation, in which the effects of opposing currents were taken into account, were applied to individual waves defined by zero-down" cross-method from irregular wave profiles. Comparisons between experimental results and the prediction by the model showed that the present model gives a good explanation for wave height distributions and the experimental finding that the surf zone is moved offshore by opposing currents.

scholarly journals RELIABILITY OF PRESSURE SENSORS TO MEASURE WAVE HEIGHT IN THE SHOALING REGION

2018 ◽  
pp. 10 ◽  
Author(s):  
Massimiliano Marino ◽  
Iván Cáceres Rabionet ◽  
Rosaria Ester Musumeci ◽  
Enrico Foti
Keyword(s):  
Wave Height ◽  
Large Scale ◽  
Surf Zone ◽  
Transfer Functions ◽  
Pressure Sensors ◽  
Experimental Dataset ◽  
Wave Flume ◽  
Intermediate Waters ◽  
The Waves

A comparison between a range of transfer functions to recover wave height from pressure sensors data is presented. The analysis is carried out by means of a large-scale wave flume experimental dataset, in which resistive, acoustic and pressure gauges recovered wave height are compared as the waves travel from intermediate waters, to the shoaling region and finally into the surf zone. All the considered transfer functions result adequate in recovering wave height in intermediate waters, becoming gradually less accurate as the steepness of the wave increases in the shoaling region and in the surf zone. The accuracy of the compared transfer functions is assessed by means of an ensemble wave height based deviation.

scholarly journals HYDRODYNAMICS UNDER LARGE-SCALE REGULAR AND BICHROMATIC BREAKING WAVES

2018 ◽  
pp. 90
Author(s):  
Dominic Van der A ◽  
Joep Van der Zanden ◽  
Ming Li ◽  
James Cooper ◽  
Simon Clark ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Surf Zone ◽  
Experimental Studies ◽  
Breaking Waves ◽  
Irregular Waves ◽  
Small Scale ◽  
Breaking Wave ◽  
Wave Flume ◽  
Cfd Models

Multiphase CFD models recently have proved promising in modelling cross‐shore sediment transport and morphodynamics (Jacobsen et al 2014). However, modelling breaking wave turbulence remains a major challenge for these models, because it occurs at very different spatial and temporal length scales and involves the interaction between surface generated turbulence and turbulence generated in the bottom boundary layer. To an extent these challenges arise from a lack of appropriate experimental data, since most previous experimental studies involved breaking waves at small-scale, and have not permitted investigation of the turbulent boundary layer processes. Moreover, most existing studies have concentrated on regular waves, thereby excluding the flow and turbulence dynamics occurring at wave group time-scales under irregular waves within the surf zone. These limitations motivated a new experiment in the large-scale CIEM wave flume in Barcelona involving regular and irregular waves. The experiment was conducted in May-July 2017 within the HYDRALAB+ Transnational Access project HYBRID.

scholarly journals WAVE HEIGHT DISTRIBUTION AND WAVE GROUPING IN SURF ZONE

1982 ◽  
Vol 1 (18) ◽  
pp. 4 ◽  
Author(s):  
Hajime Mase ◽  
Yuichi Iwagaki
Keyword(s):  
Wave Height ◽  
Surf Zone ◽  
Irregular Waves ◽  
Wave Transformation ◽  
Height Distribution ◽  
Frequency Distributions ◽  
Irregular Wave ◽  
Wave Height Distribution ◽  
Wave Heights ◽  
Deep Water Wave

The main purpose of this paper is to propose a model for prediction of the spatial distributions of representative wave heights and the frequency distributions of wave heights of irregular waves in shallow-water including the surf zone. In order to examine the validity of the model, some experiments of irregular wave transformation have been made. In addition, an attempt has been made to clarify the spatial distribution of wave grouping experimentally. Especially the present paper focuses finding the effects of the bottom slope and the deep-water wave steepness on the wave height distribution and wave grouping.

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

scholarly journals COMPUTATIONS OF LONGSHORE CURRENTS

1964 ◽  
Vol 1 (9) ◽  
pp. 12
Author(s):  
Tsao-Yi Chiu ◽  
Per Bruun
Keyword(s):  
Wave Height ◽  
Wave Breaking ◽  
Surf Zone ◽  
Wave Spectrum ◽  
Wave Theory ◽  
Breaking Wave ◽  
Height Distribution ◽  
Longshore Current ◽  
Longshore Currents ◽  
Actual Height

This article introduces the longshore current computations based on theories published under the title "Longshore Currents and Longshore Troughs" (Bruun, 1963). Two approaches are used to formulate the longshore current velocities for a beach profile with one bar under the following assumptions: (1) that longshore current is evenly distributed (or a mean can be taken) along the depthj (2) that the solitary wave theory is applicable for waves in the surf zone; (3) that the statistical wave-height distribution for a deep water wave spectrum with a single narrow band of frequencies can be used near the shore, and (4) that the depth over the bar crest, Dcr, equal 0.8Hv/i /o\. Breaking wave height H^Q/^X is designated to be the actual height equal to Hw-j (significant wave height). Diagrams have been constructed for both approaches for beach profiles with one bar, from which longshore current velocities caused by various wave-breaking conditions can be read directly. As for longshore currents along the beach with a multibar system, fifteen diagrams covering a great variety of wave-breaking conditions are provided for obtaining longshore current velocities in different troughs.

Sign in / Sign up

Export Citation Format

Share Document