Peak Wave Heights Research Articles

等高線ベース脈波特徴量と血圧値解析

This paper proposes a contour-line-based feature and analyzes its relationship with blood pressures. The proposed method extracts an existence and a variation property from the contour lines drawn on the waveform. The existence property is the total length of the contour line in the waveform. The variation property is the number of intersection points of the waveform and contour lines. The proposed feature is a quite different from the conventional feature, which is extracted from peak wave height. We made a comparative experiment whose participants are 71 females with ages ranging between 18 and 94 years. The result showed that the proposed feature was obtained highly correlation with the blood pressure than the conventional peak feature.

The nonlinear peak response distribution of structure–TLD systems during common wind events

Linearized equivalent mechanical models are often used to conduct preliminary tuned liquid damper (TLD) design; however, they cannot capture nonlinear behavior resulting from the coupling among sloshing modes. Therefore, these models underestimate the expected peak wave height, a quantity that is necessary to evaluate the required tank freeboard. In this study, a method is presented to estimate the nonlinear peak wave height using an equivalent mechanical model.A linearized equivalent mechanical model of the structure–TLD system is employed to determine the RMS responses of the structural displacement and the TLD fundamental sloshing mode wave height. Davenport’s derivation is used to estimate the probability density function of the peak structural displacement. Subsequently, the probability density function of the peak wave heights is derived using a Rayleigh–Stokes model, which employs an extended second order Stokes wave theory to estimate the nonlinear peak wave heights. Expressions are derived to calculate the mean-peak wave height as a function of the RMS response of the fundamental sloshing mode, and the fluid depth ratio.Structure–TLD system tests and nonlinear simulations are used to evaluate the model. Findings reveal that the Rayleigh model is in agreement with the experimental and simulated peak structural response distributions. In addition, the Rayleigh–Stokes model is in agreement with the experimental and particular simulated peak wave height distributions. Discrepancies are expected to arise when the fluid depth ratio is small, the excitation amplitude is large, and the damping screens are positioned to provide significant damping to the second sloshing mode.

Mass Movement-Induced Tsunami Hazard on Perialpine Lake Lucerne (Switzerland): Scenarios and Numerical Experiments

Previous studies of the sediments of Lake Lucerne have shown that massive subaqueous mass movements affecting unconsolidated sediments on lateral slopes are a common process in this lake, and, in view of historical reports describing damaging waves on the lake, it was suggested that tsunamis generated by mass movements represent a considerable natural hazard on the lakeshores. Newly performed numerical simulations combining two-dimensional, depth-averaged models for mass-movement propagation and for tsunami generation, propagation and inundation reproduce a number of reported tsunami effects. Four analysed mass-movement scenarios—three based on documented slope failures involving volumes of 5.5 to 20.8 × 106 m3—show peak wave heights of several metres and maximum runup of 6 to >10 m in the directly affected basins, while effects in neighbouring basins are less drastic. The tsunamis cause large-scale inundation over distances of several hundred metres on flat alluvial plains close to the mass-movement source areas. Basins at the ends of the lake experience regular water-level oscillations with characteristic periods of several minutes. The vulnerability of potentially affected areas has increased dramatically since the times of the damaging historical events, recommending a thorough evaluation of the hazard.

EL-Chem Viewer: A Freeware Package for the Analysis of Electroanalytical Data and Their Post-Acquisition Processing

In electrochemical sensing, a number of voltammetric or amperometric curves are obtained which are subsequently processed, typically by evaluating peak currents and peak potentials or wave heights and half-wave potentials, frequently after background correction. Transformations of voltammetric data can help to extract specific information, e.g., the number of transferred electrons, and can reveal aspects of the studied electrochemical system, e.g., the contribution of adsorption phenomena. In this communication, we introduce a LabView-based software package, ‘eL-Chem Viewer’, which is for the analysis of voltammetric and amperometric data, and enables their post-acquisition processing using semiderivative, semiintegral, derivative, integral and elimination procedures. The software supports the single-click transfer of peak/wave current and potential data to spreadsheet software, a feature that greatly improves productivity when constructing calibration curves, trumpet plots and performing similar tasks. eL-Chem Viewer is freeware and can be downloaded from www.lchem.cz/elchemviewer.htm.

In-situ wave resource assessment near Taveuni, Fiji Islands

A lack of field data, visible dominant wave activity in the northern division of Fiji Islands particularly off the southern coast of Taveuni, and increasing cost of nonrenewable energy sources coupled with associated harmful effects to the environment have led to initial wave energy resource assessment. The present work involved twelve months of on-site wave measurements commencing July 2012. The measured data were compared with a 30 yr hindcast WW3 model data from a joint project between the Bureau of Metrology, Australia (BoM) and The Pacific Australia Climate Change Science and Adaption Planning. The model was used to relate to the site characteristic in terms of significant wave-height and period in representation of Fiji's overall wave climate and at the same time validating the model with site measurements. The swell and wind wave components together with its prevailing direction was studied in detail. The calculated average power output was 12 kW/m for an average wave-height of 1 m while a peak wave-height of 3.75 m yielded power output of 24 kW/m. Comparison of the wave climate was also made with in situ wave assessment that was performed off the southern coast of Kadavu in 1994. In addition, two offshore wave energy converters' performance data (power matrix) were used to estimate the expected power generation based on the average sea states to briefly examine the site's potential with current technology. The summer and winter variation in wave power was calculated and wave power statistics such as percentile occurrence were also discussed. The results of the present study provide sufficient evidence of the potential of wave energy on site for future feasibility studies and subsequent power extraction.

The response of structures equipped with tuned liquid dampers of complex geometry

Tuned liquid dampers (TLDs) employ sloshing fluid to reduce the resonant response of structures. Existing structure-TLD models are limited to rectangular or circular tanks, shapes that may not always be feasible in practice due to geometric restrictions of the building floor plan. This paper utilizes an equivalent linearized mechanical model and a nonlinear multimodal model to predict the response of the structure-TLD systems where the TLD tank geometry is irregular. Experimental structure-TLD system tests are conducted that consider two irregular tank shapes. Response history plots and frequency response plots of the structural displacement and TLD wave heights are created to evaluate the models using the experimental results. The parent distributions and 10-minute peak distributions of the structural displacements and TLD wave heights are created for the simulated and experimental results. These distributions indicate that both the linearized and nonlinear models can accurately predict the structural response; however, the linearized model substantially underestimates the peak wave heights. Since wave heights are required to establish the required tank free board, or roof impact pressures, it is concluded that nonlinear analysis of the structure-TLD system model is required before a TLD design is finalized.

The impact of various methods of wave transfers from deep water to nearshore when determining extreme beach erosion

Several levels of increasing complexity of transferring wave information from offshore to nearshore have been studied to quantify their influence on extreme beach erosion estimates. Beach profiles which have been monitored since 1976 were used to estimate extreme beach erosion and compared to predictions. Examination of the wave propagation assumptions revolves around two types of offshore to nearshore transfer: excluding or including wave breaking and bottom friction. A second complication is whether still water level variations (ocean tide plus storm surge) are included.The inclusion of various combinations of wave propagation processes other than shoaling and refraction in the wave transfer function changes on the extreme erosion distribution tail through lowering estimates above one year return period. This brings the predicted tails closer to the observations, but does not capture the upper limit of storm demand implied by the extensive beach profile data set. Including wave breaking has a marked effect on probabilistic estimates of beach erosion. The inclusion of bottom friction is less significant. The inclusion of still water level variability in the wave transfer calculation had minimal impact on results for the case study site, where waves were transferred from offshore to water at 20m depth. These changes were put into perspective by comparing them to changes resulting from limiting beach erosion by adjusting the statistical distributions of peak wave height and storm duration to have maximum limits. We conclude that the proposed improvements on wave transformation methods are as significant as limiting wave erosion potential and worth including.

Evaluation of Seismic Rupture Models for the 2011 Tohoku-Oki Earthquake Using Tsunami Simulation

Developing a realistic, three-dimensional rupture model of the large offshore earthquake is difficult to accomplish directly through band-limited ground-motion observations. A potential indirect method is using a tsunami simulation to verify the rupture model in reverse because the initial conditions of the associated tsunamis are caused by a coseismic seafloor displacement correlating to the rupture pattern along the main faulting. In this study, five well-developed rupture models for the 2011 Tohoku-Oki earthquake were adopted to evaluate differences in simulated tsunamis and various rupture asperities. The leading wave of the simulated tsunamis triggered by the seafloor displacement in Yamazaki et al. (2011) model resulted in the smallest root-mean-squared difference (~0.082 m on average) from the records of the eight DART (Deep-ocean Assessment and Reporting of Tsunamis) stations. This indicates that the main seismic rupture during the 2011 Tohoku earthquake should occur in a large shallow slip in a narrow range adjacent to the Japan trench. This study also quantified the influences of ocean stratification and tides which are normally overlooked in tsunami simulations. The discrepancy between the simulations with and without stratification was less than 5% of the first peak wave height at the eight DART stations. The simulations, run with and without the presence of tides, resulted in a ~1% discrepancy in the height of the leading wave. Because simulations accounting for tides and stratification are time-consuming and their influences are negligible, particularly in the first tsunami wave, the two factors can be ignored in a tsunami prediction for practical purposes.

Wave forecasts using wind information and genetic programming

Forecasting of wave heights is essential for planning and operation of maritime activities. Traditionally, wave heights have been predicted using physics-based models, which rely primarily on the energy balance equation. More recently, soft computing techniques such as Artificial Neural Network (ANN), Genetic Programming (GP) have been used to generate forecasts with leads times from a few hours to several days. However, the forecast accuracy of both methods could be improved, particularly at peak wave heights, and at higher lead times. This paper forecasts the wave heights with lead times of 12h and 24h using GP. The data are obtained from two locations, along the North American and Indian coastlines. Wind information is used as an input. The modeling procedure relies heavily on the parameter kurtosis, or fourth moment. The forecasts are satisfactory, especially for the peak wave heights formed by the extreme events like hurricanes.

Evaluation of the Structure of Levee Transitions on Wave Run-Up and Overtopping by Physical Modeling

Coastal regions are continually plagued by high water levels induced by river flooding or hurricane-induced storm surge. As with any protective structure, it is essential to understand potential problematic locations that could result in structural failure and devastating loss. Common coastal protective systems are composed of floodwalls and levees, for each of which practiced methodologies have been used to estimate their performance under design conditions. Methodologies concerning spatial variability are limited, however, and transitions where earthen levees merge with floodwalls are considered areas vulnerable to erosion and possible breaching. Physical modeling of a levee tran- sition is undertaken in a three-dimensional wave basin to evaluate this hypothesis, and the detailed results of this assessment are presented in this paper. From the physical model testing, analysis of the data reveals that overtopping rates tend to be larger immediately near the transition than away from it. The run-up values and floodwall wave heights tend to show potential problematic areas and mimic the variation of overtopping along the levee transition. Under the design conditions tested, extreme overtopping conditions and associated water level values indicate that for the structure to sustain the hydraulic conditions, it must be well armored. It is shown that the variation of the still water level plays the largest role in the magnitude of the measured values, and increasing the peak wave period and wave heights also yields greater overtopping and water levels at the structure. This study highlights the need to understand specific spatial variability along coastal protective systems, and provides a better understanding of the mechanisms affecting overtopping for the specific structure tested. DOI: 10.1061/ (ASCE)WW.1943-5460.0000103. © 2012 American Society of Civil Engineers.

A comparison of estimators for the generalised Pareto distribution

The generalised Pareto distribution (GPD) is often used to model the distribution of storm peak wave heights exceeding a high threshold, from which return values can be calculated. There are large differences in the performance of various parameter and quantile estimators for the GPD. Commonly used estimation methods such as maximum likelihood or probability weighted moments are not optimal, especially for smaller sample sizes. The performance of several estimators for the GPD is compared by the Monte Carlo simulation and the implications for estimating return values of significant wave height are discussed. Of the estimators compared, the likelihood-moment (LM) estimator has close to the lowest bias and variance over a wide range of sample sizes and GPD shape parameters. The LM estimator always exists, is simple to compute and has a low sensitivity to choice of threshold. It is recommended that the LM estimator is used for calculating return values of significant wave height when the sample size is less than 500. For sample sizes above 500 the NEW estimator of Zhang and Stephens (2009) can give accurate results for low computational cost.

Estimating Return Wave Height in the Seto Inland Sea Based on Wave Hindcasting

Shallow water wave hindcasting for each of many intense storms in the past 45 years was conducted on 3 sea areas of the Seto Inland Sea using input wind distributions of the wind data acquired at on-land meteorological stations around the Inland Sea. A high quality of wave hindcasting is ensured by a reasonable agreement between the measurements and hindcasts for many cases of the peak wave height during any given storm. Extreme value analysis yields an estimate of 50-year return wave height in the areas (H50) and the H50 value ranges from 10 to 12 m in the outer area connecting to the open ocean and from 3 to 8 m in the inner area depending greatly on the topological situations. Also the effects of AM or POT-based data extraction method data period length and other factors on the estimate of H50 are discussed.

Changes in wave climate over the northwest European shelf seas during the last 12,000 years

Because of the depth attenuation of wave orbital velocity, wave‐induced bed shear stress is much more sensitive to changes in total water depth than tidal‐induced bed shear stress. The ratio between wave‐ and tidal‐induced bed shear stress in many shelf sea regions has varied considerably over the recent geological past because of combined eustatic changes in sea level and isostatic adjustment. In order to capture the high‐frequency nature of wind events, a two‐dimensional spectral wave model is here applied at high temporal resolution to time slices from 12 ka BP to present using paleobathymetries of the NW European shelf seas. By contrasting paleowave climates and bed shear stress distributions with present‐day conditions, the model results demonstrate that, in regions of the shelf seas that remained wet continuously over the last 12,000 years, annual root‐mean‐square (rms) and peak wave heights increased from 12 ka BP to present. This increase in wave height was accompanied by a large reduction in the annual rms wave‐induced bed shear stress, primarily caused by a reduction in the magnitude of wave orbital velocity penetrating to the bed for increasing relative sea level. In regions of the shelf seas which remained wet over the last 12,000 years, the annual mean ratio of wave‐ to (M2) tidal‐induced bed shear stress decreased from 1 (at 12 ka BP) to its present‐day value of 0.5. Therefore compared to present‐day conditions, waves had a more important contribution to large‐scale sediment transport processes in the Celtic Sea and the northwestern North Sea at 12 ka BP.

Influence of the El Niño–Southern Oscillation on NSW Coastal Storm Severity

The influence of the El Niño–Southern Oscillation (ENSO) on NSW coastal storm severity was investigated by comparing the yearly mean Southern Oscillation Index, , with the yearly averaged storm severity Ω measured at the NSW coast. It was found that Ω correlates well with , i.e., Ω generally increases with . The probability distributions of storm peak wave height and yearly mean SOI were also studied and were found to follow a Gumbel distribution. A simple linear relationship between extreme wave height and yearly mean SOI was then derived. At the NSW coast or at other coasts with similar wave climates, coastal recession and increased coastal damage may be expected in La Niña years, while beach recovery and reduced coastal threat may be expected in El Niñ o years.

A fuzzy–neural hybrid system of simulating typhoon waves

This study addresses a fuzzy–neural hybrid system of simulating typhoon waves. A membership function based on the fuzzy theory is expressed by a union Gaussian function to illustrate the rapid wave decaying. Four areas separated by two lines which intersect at the Hua-Lien harbor indicate the case of typhoon's position and propagation. Better simulation performance of the peak wave heights and their occurrence time in both the learning stage and the verification stage simulated by the NF2 model than by the NF1 model is identified. The wave decaying due to land effect is well described by the NF2 model. The NF2 model is applicable for well simulating typhoon waves during the whole period of a typhoon approaching to Taiwan.

Numerical Modeling of Waves at Ponce de Leon Inlet, Florida

Coastal inlets pose challenges of complex bathymetry, wave-current interaction, and influences of natural and artificial barriers for prediction of wave transformation with numerical wave models. The steady-state spectral WAVE model is described and evaluated with directional wave data measured during two storms (5.4 m and 2.4 m peak wave height) at Ponce de Leon Inlet, on the Atlantic coast of Florida. Model simulations of the two storms agreed well with measurements (within measurement uncertainty) except when incident waves were strongly nonlinear. Wave-current interaction was found to be a small influence compared to refraction by changing water depth.

On the Use of NCEP–NCAR Reanalysis Surface Marine Wind Fields for a Long-Term North Atlantic Wave Hindcast

Abstract This paper uses a state-of-the-art, third-generation wave model to evaluate the marine surface wind fields produced in the National Centers for Environmental Protection–National Center for Atmospheric Research (NCEP–NCAR) Reanalysis (NRA) project. Three alternative NRA wind fields were initially considered by assessing the resulting wave hindcasts against wave measurements in the North Atlantic Ocean. The surface 10-m wind field was found to be the most skillful and was selected for further analysis. While the wind fields from the NRA were found to be at least as skillful as the best of the analyses produced by operational Numerical Weather Prediction centers, they had significant deficiencies when compared to kinematically analyzed wind fields carried out in detailed hindcast studies. Storm peak wave heights in extratropical storms were systematically underestimated at higher sea states due to underestimation of peak wind speeds in major jet streak features propagating about intense extratropica...

Synthesis of extreme wave climate for the Canterbury Bight, New Zealand

Numerical models of the marine wind field and wave generation offer a technique for estimating the severity of extreme wave events. Measured and modelled waves in the Canterbury Bight, New Zealand, were used to examine the hypothesis that extreme conditions can be more confidently estimated by modelling the wave climate over a decade than by analysing shorter measured records. The meteorological conditions causing high waves in the Canterbury Bight were examined by inspecting wind measurements at Christchurch Airport and wave buoy measurements made in 1983–85 near the Rakaia River mouth. Although the arrival of high waves was sometimes associated with wind changes at the airport, peak wave heights generally occurred at least several hours after such wind changes and were associated with south‐westerly or southerly winds in the Bight and a depression south‐east of the South Island. Wave conditions at the buoy site for 1980–89 were modelled using marine winds obtained from a global circulation model, running a wave generation model for the seas around New Zealand, and then applying a refraction model. The decade modelled included two El Niño events and one La Niña event, and the ocean wind climate should therefore have been reasonably representative of the long‐term range of conditions. The model results were verified against the buoy measurements. Estimates of extreme wave heights were then made from 10 years of modelled record and also the measured buoy record. Application of the Gumbel distribution to the monthly maxima gave a significant wave height of 9.5 m for the wave event with an annual exceedance probability of 1 in 50. Model predictions indicate that the most severe waves arrive in the Bight from due south. Estimates of extremes from the measurements and model hindcast were close, indicating that the hindcast represents a population of events similar to those measured.

Motility Effects of Electrical Anterior Sacral Nerve Root Stimulation of the Parasympathetic Supply of the Left Colon and Anorectum in Paraplegic Subjects

The extent and nature of colonic and anorectal motility responses to S2, S3, and S4 anterior nerve root stimulation were studied in seven paraplegic patients with a Brindley electromicturition sacral implant. After sequential S2, S3 and S4 stimulation wave height activity was increased above basal from the transverse colon to the rectum. The mean motility index response to sequential stimulation was greatest at the splenic flexure. The greatest peak wave height and mean motility index response to individual anterior nerve root stimulation was to S3, which could empty the left colon by a distal motility gradient. S4 anterior root stimulation increased the intrarectal pressure and also raised the anal canal pressure to high levels.

Fluid-Particle Motion During Rotary Sloshing

This paper presents the results of a theoretical and experimental investigation of fluid-particle motion in a partially filled cylindrical tank. The body of fluid is assumed to have a steady-state motion consisting of first nonsymmetric sloshing mode only (lowest J1 mode), which gives rise to a free-surface wave that rotates around the tank at the sloshing natural frequency. It was found that theory predicts a net transport motion of the fluid particles in the direction of the free-surface waves when nonlinear terms are retained in differential equations that describe the fluid-particle displacements. Experimental measurements of the particle motion are compared with theoretical predictions. Fluid angular momentum was computed using the theoretical fluid motion and compared with the angular momentum that the fluid would possess if the fluid moved as a rigid body at the same rate as the free-surface waves. It was found that an upper bound to the ratio of the transport angular momentum to the rigid-body angular momentum was equal to 0.8 (η/a)2, where η is the peak wave height of the free surface waves and a is the tank radius.