scholarly journals ON THE INITIATION OF NEARSHORE MORPHOLOGICAL RHYTHMICITY

2011 ◽  
Vol 1 (32) ◽  
pp. 47
Author(s):  
Matthieu Andreas De Schipper ◽  
Roshanka Ranasinghe ◽  
Ad Reniers ◽  
Marcel Stive
Keyword(s):  
Numerical Model ◽  
Wave Period ◽  
Wave Group ◽  
Initiation Time ◽  
Length Scales ◽  
Long Wave ◽  
Storm Wave ◽  
Wave Conditions

Nearshore rhythmicity is often initiated in the period just after a storm where the subtidal bar is turned alongshore uniform. The initiation time as well as the length scales of the created rhythmicity varies from one storm period to another. Here we show that the post-storm wave conditions are related to the initiation of the morphological rhythmicity. Narrow-banded and long wave period, both proxies for swell waves, are often found to be present priorto the initiation of rhythmicity. Furthermore, numerical model computations illustrate that swell waves induce significantly larger wave group induced velocities on the bar. These findings imply that the arrival of swell waves can initiate and stimulate the nearshore morphological rhythmicity.

scholarly journals NUMERICAL STUDY OF NEARSHORE HYDRODYNAMICS UNDER STORM WAVE CONDITIONS IN HUJEONG BEACH, EAST COAST OF KOREA

2018 ◽  
pp. 67
Author(s):  
Yeon S. Chang ◽  
Jong Dae Do ◽  
Kyungmo Ahn ◽  
Jae-Youll Jin
Keyword(s):  
Numerical Model ◽  
East Coast ◽  
Surf Zone ◽  
Numerical Study ◽  
Navier Stokes ◽  
Model Study ◽  
Suspended Sediment Concentrations ◽  
Storm Wave ◽  
Wave Conditions ◽  
The Republic

In this study, we present the results of numerical model study to simulate the hydrodynamic conditions observed in Hujeong Beach in the east coast of the Republic of Kore from December, 2016 to January, 2017 during which several extratropical cyclones hit the area causing extreme wave conditions. Three acoustic instrumentation systems were moored from the coast to a location outside the surf zone where the water depth was ~8m to measure waves, currents and suspended sediment concentrations. For the numerical model, we employed the CADMAS-SURF Raynolds-Averaged Navier-Stokes (RANS) model to generate the wave conditions over the region of the field experiment.

scholarly journals LABORATORY EXPERIMENTS OF BICHROMATIC WAVE GROUPS PROPAGATION ON A GENTLE SLOPE BEACH PROFILE AND ENERGY TRANSFER TO LOW AND HIGH FREQUENCY COMPONENTS

2017 ◽  
pp. 6 ◽  
Author(s):  
Enrique M Padilla ◽  
Jose M Alsina
Keyword(s):  
High Frequency ◽  
Wave Breaking ◽  
Low Frequency ◽  
Primary Wave ◽  
Wave Group ◽  
Wave Groups ◽  
Long Wave ◽  
Wave Conditions ◽  
Hf Wave ◽  
Nonlinear Energy

This work presents a first analysis of experimental data studying the influence of the frequency bandwidth on the propagation of bichromatic wave groups over a constant 1:100 beach slope. The use of a large spatial cross-shore resolution and Bi-Spectral analysis techniques allows the identification of nonlinear energy transfers along the propagation of wave groups. During wave-group shoaling, nonlinear coupling between the primary wave frequencies results in a larger growth of superharmonics for narrow-banded wave conditions, increasing the skewness of the wave and leading to eventual instabilities and earlier high frequency (hf) wave breaking compared to the broad-banded wave condition. Regarding the growth of low frequency (lf) component, the data analysis has shown a larger growth of the incident bound long wave (IBLW) for broad-banded wave conditions. It is generally assumed that the transferred energy from the primary wave components to subharmonics does not affect the short wave energy budget. Here, the opposite is hypothesised, and a larger growth of the IBLW for broad-banded wave conditions is accompanied of a larger reduction of the primary wave components, a reduced growth of hf components and, consequently, a reduction in the growth of hf wave asymmetry during wave group shoaling. Conversely for narrow-banded wave conditions, a reduced IBLW growth is associated with a larger growth of hf wave asymmetry. After hf wave breaking, within the low frequency domain (lf), the IBLW decays slightly for narrow-banded conditions, consistent with a reduction in radiation stress forcing. This involves a nonlinear energy transfer from the wave group frequency back to hf components. The remaining lf energy, Outgoing Free Long Wave (OFLW), reflects back at the shoreline. However, for broad-banded wave conditions, strong dissipation and minimal reflection of lf components occurs close to the shoreline, which might be caused by lf wave breaking.

Numerical Investigation of Wave Period Influence on Long Wave Run-Up on Slope With Rigid Vegetation

2016 ◽  
Author(s):  
Jun Tang ◽  
Yongming Shen
Keyword(s):  
Shallow Water Equations ◽  
Water Wave ◽  
Wave Period ◽  
Coastal Vegetation ◽  
Coastal Structures ◽  
Rigid Vegetation ◽  
Comparison With Experiment ◽  
Long Wave ◽  
Nonlinear Shallow Water Equations ◽  
Run Up

Coastal vegetation can not only provide shade to coastal structures but also reduce wave run-up. Study of long water wave climb on vegetation beach is fundamental to understanding that how wave run-up may be reduced by planted vegetation along coastline. The present study investigates wave period influence on long wave run-up on a partially-vegetated plane slope via numerical simulation. The numerical model is based on an implementation of Morison’s formulation for rigid structures induced inertia and drag stresses in the nonlinear shallow water equations. The numerical scheme is validated by comparison with experiment results. The model is then applied to investigate long wave with diverse periods propagating and run-up on a partially-vegetated 1:20 plane slope, and the sensitivity of run-up to wave period is investigated based on the numerical results.

scholarly journals A COMPARISON OF NATURE WAVES AND MODEL WAVES WITH SPECIAL REFERENCE TO WAVE GROUPING

1980 ◽  
Vol 1 (17) ◽  
pp. 177 ◽  
Author(s):  
Hans F. Burcharth
Keyword(s):  
Phase Distribution ◽  
Random Phase ◽  
Power Spectra ◽  
Height Distribution ◽  
Wave Group ◽  
Storm Waves ◽  
Wave Height Distribution ◽  
Storm Wave ◽  
Wave Heights ◽  
The Impact

This paper represents a comparative analysis of the occurrence of wave grouping in field storm waves and laboratory waves with similar power spectra and wave height distribution. Two wave patterns - runs of waves and jumps in wave heights - which have significant influence on the impact on coastal structures were included in the analysis of storm wave records off the coasts of Cornwall, U.K. and Jutland, Denmark. Two different laboratory wave generator systems, based on random phase distribution of component waves, were used. Within the limitations given by the relatively small number of analysed records it is shown that wave group statistics can be satisfactorily reproduced by random phase generators that are not based on a limited number of component waves, but for example based on filtering of white noise. It is also shown that the statistics of large waves and wave groups containing large waves depend on whether the waves are defined from zero-upcrossings or zero-downcrossings. Although very similar seas were chosen for the analysis it was found that significant differences in the wave group statistics from the two locations existed. Also a considerable scatter in the wave group statistics throughout the storms was found.

A RANS numerical model for cross-shore beach profile evolution

2020 ◽  
Author(s):  
Julio Garcia-Maribona ◽  
Javier L. Lara ◽  
Maria Maza ◽  
Iñigo J. Losada
Keyword(s):  
Sediment Transport ◽  
Numerical Model ◽  
Transport Model ◽  
Numerical Models ◽  
Computational Cost ◽  
Physical Modelling ◽  
Computational Effort ◽  
Beach Profile ◽  
Time Step ◽  
Wave Conditions

<p>The evolution of the cross-shore beach profile is tightly related to the evolution of the coastline in both small and large time scales. Bathymetry changes in extreme maritime events can also have important effects on coastal infrastructures such as geotechnical failures of foundations or the modification of the incident wave conditions towards a more unfavourable situation.</p><p>The available strategies to study the evolution of beach profiles can be classified in analytical, physical and numerical modelling. Analytical solutions are fast, but too simplistic for many applications. Physical modelling provides trustworthy results and can be applied to a wide variety of configurations, however, they are costly and time-consuming compared to analytical strategies. Finally,  numerical approaches offer different balances between cost and precision depending on the particular model.</p><p>Some numerical models provide greater precision in the beach profile evolution, but incurring in a prohibitive computational cost for many applications. In contrast, the less expensive ones assume simplifications which do not allow to correctly reproduce significant phenomena of the near-shore hydrodynamics such as wave breaking or undertow currents, neither to predict important features of the beach profile like breaker bars.</p><p>In this work, a new numerical model is developed to reproduce the main features of the beach profile and hydrodynamics while maintaining an affordable computational cost. In addition, it is intended to reduce to the minimum the number of coefficients that the user has to provide to make the model more predictive.</p><p>The model consists of two main modules. Firstly, the already existing 2D RANS numerical model IH2VOF is used to compute the hydrodynamics. Secondly, the sediment transport model modifies the bathymetry according to the obtained hydrodynamics. The new bathymetry is then considered in the hydrodynamic model to account for it in the next time step.</p><p>The sediment transport module considers bedload and suspended transports separately. The former is obtained with empirical formulae. In the later,the distribution of sediment concentration in the domain is obtained by solving an advective-diffusive transport equation. Then, the sedimentation and erosion rates are obtained along the seabed.<br>Once these contributions are calculated, a sediment balance is performed in every seabed segment to determine the variation in its level.</p><p>With the previously described strategy, the resulting model is able to predict not only the seabed changes due to different wave conditions, but also the influence of this new bathymetry in the hydrodynamics, capturing features such as the generation of a breaker bar, displacement of the breaking point or variation of the run-up over the beach profile. To validate the model, the numerical results are compared to experimental data.</p><p>An important novelty of the present model is the computational effort required to perform the simulations, which is significantly smaller than the one associated to existing models able to reproduce the same phenomena.</p>

Gold-black as IR absorber and solar cell enhancer

2009 ◽  
Vol 1208 ◽  
Author(s):  
Robert E. Peale ◽  
Justin W Cleary ◽  
Masahito Ishigami ◽  
Christian W Smith ◽  
Kevin Baillie ◽  
...  
Keyword(s):  
Characteristic Length ◽  
Thin Film Solar Cells ◽  
Photoelectron Emission ◽  
Conducting Film ◽  
Length Scales ◽  
Near Ir ◽  
Long Wave ◽  
Deposition Parameters ◽  
Plasmon Resonances ◽  
Film Polymer

AbstractInfrared absorbance and visible/near-IR excited plasmon resonances are investigated in gold-black, a porous nano-structured conducting film. Polymer infusion (for hardening) generally reduced absorbance in the long wave IR but has little effect at THz wavelengths. The characteristic length scales of the structured films vary considerably as a function of deposition parameters, but the absorbance is found to be only weakly correlated with these distributions. Initial investigations of gold-black by photoelectron emission microscopy (PEEM) reveal plasmon resonances, which have potential to enhance the efficiency of thin film solar cells. For films with different characteristic length scales, the plasmon resonances appear in structures with similar length scales.

scholarly journals Safety Traffic Control for a Coastal Bridge Constructed on a Reef under Storm Wave Conditions

2007 ◽  
Vol 54 ◽  
pp. 926-930
Author(s):  
Katsutoshi KIMURA ◽  
Hajime WATANABE ◽  
Yasuji YAMAMOTO ◽  
Tsutomu OKADA ◽  
Takao NAKOSHI ◽  
...  
Keyword(s):  
Traffic Control ◽  
Storm Wave ◽  
Wave Conditions

scholarly journals MOVABLE-BED MODEL STUDIES OF PERCHED BEACH CONCEPT

1972 ◽  
Vol 1 (13) ◽  
pp. 60
Author(s):  
C.B. Chatham
Keyword(s):  
Three Dimensional ◽  
Normal Wave ◽  
Beach Erosion ◽  
Model Studies ◽  
Model Study ◽  
Wide Range ◽  
Final Design ◽  
Storm Wave ◽  
Wave Conditions ◽  
Movable Bed

Hydraulic model studies were conducted to aid in ascertaining the technical feasibility and optimum design factors of the perched beach concept. Among these were two-dimensional, movable-bed studies to determine an estimate of the amount of sand which would be lost seaward over the submerged toe structure by normal and storm wave action, the optimum elevation of the submerged toe structure, and the length of a stone blanket required to reduce seaward migration of sand to a minimum. The model beach was subjected to test waves until equilibrium was reached for a wide range of wave conditions for both the existing beach and the perched beach. Test results indicate that (a) little or no beachfill material will be lost seaward of the toe structure for normal wave conditions but the larger storm waves may cause erosion of the perched beach, (b) the installation of a stone blanket shoreward of the toe structure will reduce the amount of beach erosion, (c) if the beach fill is extended a sufficient distance seaward, the toe structure serves no useful purpose, and (d) a three-dimensional movable-bed model study is feasible and is necessary to determine the final design features of a perched beach.

Generating Power From Ocean Waves Using a Float With Excessive Buoyancy: Theory and Dynamic Model Results

2003 ◽  
Author(s):  
T. MacCready ◽  
T. Zambrano ◽  
B. D. Hibbs
Keyword(s):  
Numerical Model ◽  
Natural Frequency ◽  
Power Output ◽  
Ocean Surface ◽  
Ocean Waves ◽  
The Body ◽  
Energy Extraction ◽  
Ocean Energy ◽  
Wave Conditions ◽  
Rich Data

We are exploring a new approach to ocean energy extraction through a device that we refer to as the NAF (an acronym for Non-Archimedean Float). The NAF is a fully submerged body with excess buoyancy; i.e., the mass of the body is far less than the mass of the water it displaces. When such a float is tethered beneath the ocean surface the buoyancy yields a large force vector in the direction perpendicular to the isobaric surfaces that parallel the water/air interface. The constant shifting of the wave troughs provides the opportunity for energy extraction using turbines affixed to the float. We are exploring the NAF concept because its simplicity results in many inherent benefits. The device has few moving parts, gathers energy from waves coming in any direction, and exists as a non-obtrusive, completely submerged installation. A numerical model of the NAF has been created to determine the dynamic behavior and power output for various configurations and under various wave conditions. The numerical model is set up to calculate the various forces experienced by the NAF float, and from these it calculates the velocity and position of the float through time series steps. The model effectively demonstrates which variables are important and how power output relates to NAF dimensions. One early finding from the model result relates to tuning the natural frequency of the NAF to match the natural frequency of the waves. The NAF moves like an inverted pendulum, and its natural frequency is primarily dependent on the length of the pendulum. Regardless of the actual float buoyancy, the 6 to 12 second periods that typify average wave conditions dictate that the NAF tether should be between 30-m and 60-m long. Also, a scale version of this novel energy device consisting of a float tethered beneath the ocean surface was deployed off the coast of southern California. The deployment yielded rich data sequences that are sufficient for comparison with a dynamic numerical model.

scholarly journals The Smart Detection of Ship Severe Roll Motions and Decision-Making for Evasive Actions

2020 ◽  
Vol 8 (6) ◽  
pp. 415
Author(s):  
Maria Acanfora ◽  
Flavio Balsamo
Keyword(s):  
Decision Making ◽  
Numerical Model ◽  
Wave Period ◽  
Ship Motions ◽  
Parametric Roll ◽  
Control Delay ◽  
Ship Dynamics ◽  
Speed Change ◽  
Parametric Roll Resonance

This paper presents a numerical model for the smart detection of synchronous and parametric roll resonance of a ship. The model implements manoeuvring equations superimposed onto ship dynamics in waves. It also features suited autopilot and rudder actuator models, aiming at a fair depiction of the control delay. The developed method is able to identify and distinguish between synchronous and parametric roll resonance, based on the estimation of encounter wave period from ship motions. Therefore, it could be useful as a smart tool for manned vessels and, also, in the perspective of unmanned and autonomous vessels (in the paper it is assumed a hypothetical remote crew). Once the resonance threat is identified, different evasive actions are simulated and compared, based on course and speed change. Calculations are carried out on a ro-ro pax vessel vulnerable to parametric roll. We conclude that, in roll resonance situations, and in the absence of roll stabilisation systems on-board, course change could be the most effective countermeasure.

Sign in / Sign up

Export Citation Format

Share Document