Do longshore bars shelter the shore?

2000 ◽  
Vol 404 ◽  
pp. 251-268 ◽  
Author(s):  
JIE YU ◽  
CHIANG C. MEI
Keyword(s):  
Spatial Distribution ◽  
Incident Wave ◽  
Wave Energy ◽  
Phase Relation ◽  
Bragg Reflection ◽  
Qualitative Change ◽  
Numerical Calculations ◽  
Reflected Waves ◽  
Incident Waves ◽  
Incident Wave Energy

In most past theories on Bragg reflection of waves by a finite patch of rigid bars, only outgoing waves are allowed on the transmission side, simulating the effect of an idealized shoreline where all the incident wave energy is consumed by breaking. In these theories the amplitudes of both the incident and reflected waves are found to decrease monotonically over the bar patch in the shoreward direction. This result has motivated the idea of artificially constructing bars to protect a beach from incident waves. However, some numerical calculations have suggested that this tendency does not always hold when there is some reflection from the shore. We show here that with finite reflection by the shoreline the spatial distribution of wave energy over the patch can indeed be reversed, indicating that the mechanism can increase the hazards to the beach. The phase relation between the bars and the shoreline reflection is found to be the key to this qualitative change of wave response.

scholarly journals BEACH PROFILES AT TORREY PINES, CALIFORNIA

1976 ◽  
Vol 1 (15) ◽  
pp. 75 ◽  
Author(s):  
David G. Aubrey ◽  
Douglas L. Inman ◽  
Charles E. Nordstrom
Keyword(s):  
Sediment Transport ◽  
Incident Wave ◽  
Wave Energy ◽  
Energy Conditions ◽  
Beach Profile ◽  
High Wave ◽  
Wave Characteristics ◽  
Spectral Estimates ◽  
High Wave Energy ◽  
Incident Waves

Beach profiles have been measured at Torrey Pines Beach, California for four years and correlated with tides and accurate spectral estimates of the incident wave field. Characteristic equilibrium beach profiles persist for time spans of up to at least two weeks in response to periods of uniform incident waves. These changes in the beach profiles are primarily due to on-offshore sediment transport which can be related to variations in wave characteristics and tidal phase. The most rapid readjustment of the beach profile occurs during high wave energy conditions coincident with spring tides. Alternatively, the highest berm building is associated with moderate to low waves that coincide with spring tides.

Numerical and Experimental Investigations of Wave Field Around a Circular Island with the Presence of Weak Currents

2002 ◽  
Vol 18 (1) ◽  
pp. 35-42
Author(s):  
Ming-Chung Lin ◽  
Chao-Min Hsu ◽  
Shou-Cheng Wang ◽  
Chao-Lung Ting
Keyword(s):  
Experimental Data ◽  
Wave Field ◽  
Wave Height ◽  
Incident Wave ◽  
Numerical Calculations ◽  
Experimental Investigations ◽  
Wave Refraction ◽  
Circular Island ◽  
Incident Waves ◽  
A Current

ABSTRACTThis study elucidated the complicated phenomena of wave refraction and diffraction around a circular island due to random incident waves traveling with a current. Various combinations of random incident wave and current conditions were used to investigate the wave height distributions around a circular island numerically and experimentally. Numerical calculations were carried out based on the theory derived by Lin & Hsu [1]. According to the results, it shows that numerical calculations can predict experimental data quantitatively well.

Submerged Floating Breakwaters

1991 ◽  
Vol 113 (3) ◽  
pp. 205-210 ◽  
Author(s):  
D. V. Evans ◽  
C. M. Linton
Keyword(s):  
Circular Cylinder ◽  
General Theory ◽  
Incident Wave ◽  
Vertical Plate ◽  
Appreciable Amount ◽  
Submerged Body ◽  
Floating Breakwaters ◽  
Incident Waves ◽  
Incident Wave Energy ◽  
Horizontal Circular Cylinder

In this paper we show how a submerged body can, if properly tuned to the incoming waves, reflect an appreciable amount of the incident wave energy by creating waves through its own motion which effectively cancel the incident waves passing over it. A general theory for this phenomenon is described which is applied to the cases of a hinged vertical plate and a submerged tethered horizontal circular cylinder.

Evaluation of Incident Wave Energy in Flume Tests

1987 ◽  
Author(s):  
Eliezer Kit ◽  
Oded Gottlieb ◽  
Dov S. Rosen
Keyword(s):  
Incident Wave ◽  
Wave Energy ◽  
Flume Tests ◽  
Incident Wave Energy

scholarly journals FIELD EXPERIMENT ON BEACH GRAVEL TRANSPORT

1978 ◽  
Vol 1 (16) ◽  
pp. 101 ◽  
Author(s):  
Masataro Hattori ◽  
Takasuke Suzuki
Keyword(s):  
Field Experiment ◽  
Incident Wave ◽  
Wave Energy ◽  
Transport Processes ◽  
Central Japan ◽  
Selective Transport ◽  
Longshore Transport ◽  
Wave Energy Flux ◽  
The Mean ◽  
Incident Wave Energy

To examine the longshore transport processes of beach gravels under wave action, a field experiment was performed by tracing the dacite blocks injected on Fuji Coast, Shizuoka Prefecture, Central Japan. The mean dislocating velocity of the tracer was 2 to 3 m/day under normal sea conditions, while under storm conditions it reached about 400 m/day. This -velocity was fairly proportional to the longshore component of incident wave energy flux. The longshore variations of the size and shape of beach gravels were mainly resulted from the progressive attrition and impact breakage of beach gravels rather than from the selective transport.

scholarly journals RESEARCHES ON SEA-WALLS

1970 ◽  
Vol 1 (12) ◽  
pp. 88
Author(s):  
S. Nagal
Keyword(s):  
Incident Wave ◽  
Wave Energy ◽  
Precast Concrete ◽  
Recent Decade ◽  
Point Of View ◽  
Industrial Firms ◽  
Wave Overtopping ◽  
Port Facilities ◽  
Sea Wall ◽  
Incident Wave Energy

In the recent decade, very wide areas of sea where the depths of water are from several meters to ten meters or more during storms have been reclaimed for industrial firms and port facilities in many places in Japan As the incident wave energy in such cases is very large at the sea-walls, the protection of the reclaimed lands from wave overtopping by the conventional sea-walls of vertical type or composite-slope«and-berai type is generally impossible from an economical point of view In Japan a special type of sea-wall, which is of such a type that a rubble-mound covered with specially shaped precast concrete armor blocks is built in front of the sea-wall to absorb most of the incident wave energy, has been constructed to protect the reclaimed lands from wave overtopping Most of the seawalls have been proved satisfactory after passing of typhoons over or near the sea-walls The design of the sea-walls is presented here in by showing the comparisons between the experiments and prototypes during typhoons.

Model Experiment on an OWC-Type Wave-Energy Converter With Hydraulic Power Take-Off

2002 ◽  
Author(s):  
Torkel Bjarte-Larsson ◽  
Per Magne Lillebekken ◽  
Jo̸rgen Hals ◽  
Johannes Falnes
Keyword(s):  
Incident Wave ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Laboratory Model ◽  
Energy Converter ◽  
Hydraulic Power ◽  
Optimum Load ◽  
Wave Channel ◽  
Period 2 ◽  
Incident Wave Energy

A wave-energy converter of the OWC type is described, in which the absorbed wave energy is converted to useful energy by means of a hydraulic power take-off. Means are provided to enable the float to be latched for phase control. The float is connected to a piston pump, which pumps water from the level of the water in the wave channel to a higher level, which is adjustable. By means of measurements from three wave gauges (two on the upstream side and one on the downstream side) the incident wave energy and the absorbed wave energy are derived. For a down-scaled laboratory model, resonance is obtained with an incident sinusoidal wave of period 1 s. With optimum load, the converted useful hydraulic energy is a fraction of 0.2 of the incident wave energy. The absorbed wave energy is then 0.6 units of the incident wave energy. With wave period 2 s and optimum load, these energy fractions are 0.03 and 0.13, which are increased to 0.05 and 0.21, respectively, when latching control is applied.

Regularly-spaced grooves on shore platforms in north Northumberland, UK

2020 ◽  
Vol 63 (2) ◽  
pp. 124-134
Author(s):  
Alison M. Tymon ◽  
Barry G. Tymon
Keyword(s):  
Incident Wave ◽  
Wave Energy ◽  
Surf Zone ◽  
High Water ◽  
Edge Waves ◽  
Shore Platform ◽  
Bedding Planes ◽  
High Water Mark ◽  
Incident Wave Energy ◽  
Shore Platforms

Unusual regularly-spaced grooves are found between low water mark (LWM) and high water mark (HWM) on several shore platforms in north Northumberland. References in the literature are sparse, so data were collected to establish the nature of the grooves and to elucidate the processes that might have formed them. Groove formation is confined to strata with widely spaced bedding planes on shore platforms dipping at no more than 5° towards the sea. The grooves are symmetrical, bifurcation is common and grooves on sandstones are deeper and more sinuous than those on limestones. Grooves at mid-tide levels are wider than grooves near LWM and HWM and the trend of the grooves is not related to joint trends. The process that has formed the characteristically smooth surfaces of the grooves is considered to be abrasion by sand and pebbles carried by waves in the surf zone of the shore platform. The width of the grooves is remarkably regular, and it is suggested that this may be due to the effects of the increase in incident wave energy given by edge waves.

scholarly journals EVALUATION OF INCIDENT WAVE ENERGY IN FLUME TEST

1986 ◽  
Vol 1 (20) ◽  
pp. 93
Author(s):  
Eliezer Kit ◽  
Oded Gottlieb ◽  
Dov S. Rosen
Keyword(s):  
Least Squares ◽  
Incident Wave ◽  
Wave Energy ◽  
Least Squares Method ◽  
Stationary Wave ◽  
Residual Energy ◽  
Irregular Waves ◽  
Wave Spectra ◽  
Reflected Wave ◽  
Incident Wave Energy

A two dimensional model study, carried out for a structure in a flume using irregular waves, presents the problem of determining the relationship between the total incident wave energy attacking the structure and its response to that attack (displacements, forces, etc.) in various sea states, The total incident wave energy can be evaluated indirectly only, because the wave energy measured in the flume contains an extent of residual wave energy in addition to that generated by the wave machine. This residual energy consists of the re-reflected wave energy from the paddle of the wave machine, assuming the existence of quasi-stationary wave conditions in the flume. A method originally presented by Gravesen et al. (1974), was applied in this study to evaluate the total incident wave energy. In view of the results obtained by this method, a physically more sound refinement is proposed for the evaluation of the total incident wave energy (and characteristic wave height). Results of model tests were analyzed by the CAMERI refinement and compared with the Gravesen method and with a cross-spectral least squares method, separating incident and reflected wave spectra from wave spectra measured in the flume, Good agreement was found between the results obtained employing the CAMERI refinement and the cross-spectral least squares method, Advantages and drawbacks of these methods are indicated,

Sign in / Sign up

Export Citation Format

Share Document