Elevation Energy Research Articles

Energy and dissipation spectra of waves propagating in the inner surf zone

The spectral behaviour of random sawtooth waves propagating in the inner surf zone is investigated in this study. We show that the elevation energy spectrum exhibits a universal shape with an $\omega ^{-2}$ tendency in the inertial subrange and an exponential decay in the diffusive subrange ( $\omega$ being the angular frequency). A theoretical spectrum is derived based on the similarities between sawtooth waves in the inner surf zone and Burgers wave solutions. Very good agreement is shown between this theoretical spectrum and laboratory experiments covering a large range of incident random wave conditions. Additionally, an equation describing the universal shape of the dissipation spectrum is derived. It highlights that the dissipation spectrum is nearly constant in the inertial subrange, consistent with prior laboratory observations. The findings presented in this study can be useful to improve broken wave dissipation parametrizations in stochastic spectral wave models.

Efficient Calculation and Visualization of Energy Grade Line (EGL) and Hydraulic Grade Line (HGL) in Fluid Flow Systems

The goal of this project is to use MATLAB software to efficiently calculate and visually represent the Energy Grade Line (EGL) and Hydraulic Grade Line (HGL) in fluid flow systems. This work serves as a practical showcase of our how MATLAB can be used to make Bernoulli calculations in the realm of civil engineering. In addition, the incorporation of Building Information Modeling (BIM) offers the potential to further enhance the design and analysis of fluid flow systems. The Energy Grade Line (EGL) holds a vital position in fluid mechanics, acting as a representation of a fluid's energy as it moves through a conduit. This blend of pressure, velocity, and elevation energy provides crucial insights into the behavior and characteristics of the fluid throughout its course. For engineers, the EGL is an essential tool, aiding in the analysis of fluid flow systems, identification of energy losses, and optimization of hydraulic structures. Furthermore, the Hydraulic Grade Line (HGL) represents another critical concept in fluid mechanics, graphically illustrating the pressure head of fluid along a specified route. It offers a clear depiction of energy distribution within a fluid flow system, accounting for the sum of pressure and elevation heads. Engineers heavily rely on the HGL to inspect pressure fluctuations, detect potential issues like pressure drops or excessive velocities, and make informed decisions to ensure fluid flow's efficiency and reliability. Thorough testing and implementation revealed that, with precise configuration of the MATLAB environment code, our code achieves high accuracy calculations for Energy Grade Line (EGL) and Hydraulic Grade Line (HGL) values. This setup also enables the generation of clear graphical representations, providing engineers with a reliable and visually accessible graph for fluid flow system analysis.

A two-dimensional semi-analytic solution on two-layered liquid sloshing in a rectangular tank with a horizontal elastic baffle

A semi-analytic study on two-layered liquid sloshing in a horizontal excited two-dimensional rectangular tank with a horizontal elastic baffle was performed. The present work is a further development of the semi-analytical technique for solving the single-layer liquid sloshing problem. The horizontal elastic baffle was located in the lower liquid or upper liquid. First, the complex liquid domain in a baffled tank was divided into several simple sub-domains to solve the analytic solution. The wet mode of a horizontal baffle was presented according to the Eulerian Bernoulli beam. The continuity boundary condition on the interfaces between two liquids and the virtual interfaces was given. Then, the formal solution was derived for each sub-domain and a horizontal baffle using the superposition principle and the method of separation of variables. Then, the total velocity potential subject to lateral excitation was summed over the container potential function and the liquid disturbance potential. The dynamic response equation for two-layered liquid sloshing was established. Multiple methods verified the semi-analytic solution's correctness and agreed well with other methods. Finally, the numerical analysis mainly shows that the density ratio becomes more significant for the coupled frequency when the baffle is in the upper liquid. A large baffle's width suppresses the liquid flow in the baffled tank effectively. Furthermore, adjusting the baffle and the layered liquid parameters can significantly suppress layered liquid sloshing. For the seismic response, the elevation energy is mainly located after 2.5 s.

Seismic Signal Characteristics and Numerical Modeling Analysis of the Xinmo Landslide

Due to the high elevation and huge potential energy of high-level landslides, they are extremely destructive and have prominent kinetic-hazard effects. Studying the kinetic-hazard effects of high-level landslides is very important for landslide risk prevention and control. In this paper, we focus on the high-level landslide that occurred in Xinmo on 24 June 2017. The research is carried out based on a field geological survey, seismic signal analysis, and the discrete element method. Through ensemble empirical mode decomposition (EEMD) and Fourier transformation, it is found that the seismic signals of the Xinmo landslide are mainly located at low frequencies of 0–10 Hz, and the dominant frequency range is 2–8 Hz. In addition, the signal time-frequency analysis and numerical simulation calculation results reveal that the average movement distance of the sliding body was about 2750 m, and the average movement speed was about 22.9 m/s. The movement process can be divided into four main stages: rapid start, impact loading, fragmentation and migration, and scattered accumulation stages. We also provide corresponding suggestions for the zoning of high-level landslide geological hazards.

Optimal Estimation of the Peak Wave Period using Smoothing Method

In this study, a smoothing method was applied to improve the accuracy of peak wave period estimation using the water surface elevation observed from the Oceanographic and Meteorological Observation Tower located on the west coast of the Korean Peninsula. Validation of the application of the smoothing method was performed using variance of the surface elevation and total amount wave energy, and then the effect on the application of smoothing was analyzed. As a result of the analysis, the correlation coefficient between variance of the surface elevation and total amount wave energy was 0.9994, confirming that there was no problem in applying the method. Thereafter, as a result of reviewing the effect of smoothing, it was found to be reduced by about 4 times compared to the confidence interval of the existing estimated spectrum, confirming that the accuracy of the estimated peak wave period was improved. It was found that there was a statistically significant difference in probability density between 4 and 6 seconds due to the smoothing application. In addition, for optimal smoothing, the appropriate number of smoothings according to the significant wave height range was calculated using a statistical technique, and the number of smoothings was found to increase due to the unstable spectral shape as the significant wave height decreased.

Harnessing island–ocean connections to maximize marine benefits of island conservation

Islands support unique plants, animals, and human societies found nowhere else on the Earth. Local and global stressors threaten the persistence of island ecosystems, with invasive species being among the most damaging, yet solvable, stressors. While the threat of invasive terrestrial mammals on island flora and fauna is well recognized, recent studies have begun to illustrate their extended and destructive impacts on adjacent marine environments. Eradication of invasive mammals and restoration of native biota are promising tools to address both island and ocean management goals. The magnitude of the marine benefits of island restoration, however, is unlikely to be consistent across the globe. We propose a list of six environmental characteristics most likely to affect the strength of land–sea linkages: precipitation, elevation, vegetation cover, soil hydrology, oceanographic productivity, and wave energy. Global databases allow for the calculation of comparable metrics describing each environmental character across islands. Such metrics can be used today to evaluate relative potential for coupled land–sea conservation efforts and, with sustained investment in monitoring on land and sea, can be used in the future to refine science-based planning tools for integrated land–sea management. As conservation practitioners work to address the effects of climate change, ocean stressors, and biodiversity crises, it is essential that we maximize returns from our management investments. Linking efforts on land, including eradication of island invasive mammals, with marine restoration and protection should offer multiplied benefits to achieve concurrent global conservation goals.

ISPH Simulation of Solitary Waves Propagating Over a Bottom-Mounted Barrier With k–ε Turbulence Model

Solitary wave propagating over a bottom-mounted barrier is simulated using the Incompressible Smoothed Particle Hydrodynamics (ISPH) method in order to study the generation and transport of turbulence associated with flow separation around submerged structures. For an accurate capture of turbulence characteristics during the wave propagation, rather than employing the standard sub-particle scale (SPS) model, the k-ε turbulence model is coupled with the numerical scheme. The results of the numerical model are compared with experimental data, and good agreement is observed in terms of mean velocity, free surface elevation, vorticity fields and turbulent kinetic energy. The numerical model is then employed to investigate the effects of wave non-linearity and geometrical size of the submerged barrier on the flow separation; and calculate the reflection, dissipation and transmission coefficients to evaluate the importance of energy dissipation due to the generation of vortices. The results of this study show that the developed ISPH method with the k-ε turbulence closure model is capable of reproducing the velocity fields and the turbulence characteristics accurately, and thus can be used to perform predictions of comprehensive hydrodynamics of flow-structure interactions in the urban hydro-environment systems.

Background stratification impacts on internal tide generation and abyssal propagation in the western equatorial Atlantic and the Bay of Biscay

Abstract. The forthcoming SWOT altimetric missions aim to resolve the mesoscale with an unprecedented spatial resolution and swath. However, high-frequency processes, such as tides, are undersampled in time and aliased onto lower frequencies, so they need to be corrected properly. Unlike barotropic tides, internal tides (ITs) are not completely stationary and have significant temporal variability due to their interactions with the ocean circulation and the stratification variability. Stratification changes impact both the generation and the propagation of ITs. The present study proposes a methodology to quantify the impacts of background stratification using a clustering method for the classification of a broad range of stratification and idealized modeling of ITs in the frequency domain. The methodology is successfully tested in the western equatorial Atlantic and in the Bay of Biscay. For the western equatorial Atlantic, a single pycnocline is observed and only the two first vertical modes of ITs have significant amplitudes. With no variation in the stratification intensity, the variation in the depth of this single pycnocline linearly impacts the elevation amplitude, energy fluxes and surface wavelength of the two modes. In the Bay of Biscay, there is a permanent deep pycnocline and secondary seasonal pycnoclines near the surface. No proxy have been found to describe the changes in ITs, so a seasonal climatology is explored. The seasonality of the stratification strongly affects the elevation amplitudes as well as the energy fluxes of modes 1, 2 and 3. The distribution of the modes vary with the background stratification, changing the horizontal scales of the ITs.

The Effect of the Choice of the Nodal Plane on Tsunami Energy Estimates

Data on earthquake focal mechanisms from the Bulletin of the International Seismological Center (ISC) have been used to study the effect of the choice of the nodal plane on the estimate for potential energy of the initial elevation in the tsunami source. For the majority of seismic events, the energy estimate has been shown to weakly depend on the choice of the nodal plane. However, in some rare cases, the energy estimates can differ significantly (by up to one order of magnitude). Usually, these significant differences are characteristic of strong shallow earthquakes, i.e., the seismic events that can effectively generate tsunami waves. In all cases when the ratio of the rupture length to the earthquake depth is small the choice of the nodal plane has almost no effect on the energy estimate.

Propagation of Solitary Waves over a Submerged Slotted Barrier

In this article, the interaction of solitary waves and a submerged slotted barrier is investigated in which the slotted barrier consists of three impermeable elements and its porosity can be determined by the distance between the two neighboring elements. A new experiment is conducted to measure free surface elevation, velocity, and turbulent kinetic energy. Numerical simulation is performed using a two-dimensional model based on the Reynolds-Averaged Navier-Stokes equations and the non-linear k-ɛ turbulence model. A detailed flow pattern is illustrated by a flow visualization technique. A laboratory observation indicates that flow separations occur at each element of the slotted barrier and the vortex shedding process is then triggered due to the complicated interaction of those induced vortices that further create a complex flow pattern. During the vortex shedding process, seeding particles that are initially accumulated near the seafloor are suspended by an upward jet formed by vortices interacting. Model-data comparisons are carried out to examine the accuracy of the model. Overall model-data comparisons are in satisfactory agreement, but modeled results sometimes fail to predict the positions of the induced vortices. Since the measured data is unique in terms of velocity and turbulence, the dataset can be used for further improvement of numerical modeling.

Forest quality-based assessment of the Returning Farmland to Forest Program at the community level in SW China

The Returning Farmland to Forest Program (RFFP) has played an important role in controlling soil erosion, increasing vegetation cover, and transforming rural livelihoods in China. The program may promote vegetation restoration, increase the proportion of households engaged in off-farm labor, and improve forest management, and thus contribute to enhanced forest quality. However, studies of RFFP’s impact on forest quality at the community level remain inadequate. The purpose of this study was to test the following hypothesis: that RFFP implementation would lead to a significant difference in forest quality between communities with RFFP implementation versus those without. Twelve communities in Southwest China were selected as subjects, all being rich in biological and cultural diversity but have high poverty rates. We conducted a linked analysis combining forest quality data with socio-economic data to examine the effectiveness of RFFP at the community level. Forest community data were obtained through field surveys in July–August 2014, and socio-economic data was collected using a questionnaire survey. A forest quality index system was constructed using factor analysis, and the difference in forest quality between village that did and did not implement RFFP were compared. Key environmental and socio-economic variables affecting forest quality were identified by a constrained ordination method. Our results show that neither the structure, diversity, biomass nor soil fertility of the forest communities were not differed significantly between the village communities with and without RFFP. Elevation, fuelwood harvesting and solar energy projects contributed markedly to forest quality, suggesting that the RFFP probably did not directly drive the existing differences in forest quality among the 12 communities. Both natural and socio-economic factors affect forest quality. Considering current rural livelihood needs and the goals of expanding forest cover and improving forest quality, ensuring that land users have a meaningful voice in decisions about forest regeneration and establishing compensation mechanisms for forest management may be key directions to pursue in the future for sustainable development.

Evaluation of turbulence closure models under spilling and plunging breakers in the surf zone

Turbulence closure models are evaluated for application to spilling and plunging breakers in the surf zone using open source computational fluid dynamics software. A new library of turbulence models for application to multiphase flows has been developed and is assessed for numerical efficiency and accuracy by comparing against existing laboratory data for surface elevation, velocity and turbulent kinetic energy profiles. Out of the models considered, it was found that, overall, the best model is the nonlinear k-ϵ model. The model is also shown to exhibit different turbulent characteristics between the different breaker types, consistent with experimental data.

Ensemble lightning prediction models for the province of Alberta, Canada

Lightning is a major cause of wildland fires in Canada. During an average year in the province of Alberta, 330 000 cloud-to-ground lightning strikes occur. These strikes are responsible for igniting 45% of reported wildfires (~450 fires) and 71% of area burned (~105 000 ha). Lightning-caused wildland fires in remote areas have large suppression costs and a greater chance of escaping initial attack when compared with human-caused fires, which are often located close to infrastructure and suppression resources. In this study, geographic and temporal covariates were paired with meteorological reanalysis and radiosonde observations to generate a series of 6-h and 24-h lightning prediction models valid from April to October. These models, based on cloud-to-ground lightning from the Canadian Lightning Detection Network, were developed and validated for the province of Alberta, Canada. The ensemble forecasts produced from these models were most accurate in the Rocky Mountain and Foothills Natural Regions, achieving hits rates of 85%. The Showalter index, latitude, elevation, longitude, Julian day and convective available potential energy were found to be highly important predictors. Random forest classification is introduced as a viable modelling method to generate lightning forecasts.

A ten-year analysis of cloud-to-ground lightning activity over the Eastern Mediterranean region

Lightning activity is analysed in a sector covering the Eastern Mediterranean (16–32°E, 34–46°N) for the years 2005–2014. The study is based on the use of cloud-to-ground (CG) lightning activity data retrieved from ZEUS system, operated by the National Observatory of Athens, and examines the seasonal, diurnal and spatial variability of the lightning activity. The effect of elevation, terrain slope, vegetation cover and convective available potential energy (CAPE) on the distribution of the CG lightning strokes is also investigated. Lightning is modulated by the diurnal cycle of insolation and the underlying topographic features of the region. The lightning strokes are more numerous over the mainland than over the sea. CG lightning activity is dominant over the land and the coastal areas during spring and summer while during the coldest period of the year it is dominant over the sea. The maximum value of lightning activity is observed in June and mostly in the afternoon. The orography and the terrain slope affect the distribution of lightning. During the warmest period of the year, the forested areas have an increased “lightning yield”. The number of CG lightning strokes increases with increasing CAPE and the high correlation between them indicates that CAPE values could be used as a proxy for the presence of lightning activity, at least over the eastern Mediterranean region.

The properties of co-seismic deformations of the ocean bottom as indicated by the slip-distribution data in tsunamigenic earthquake sources

In this study we consider 75 ocean-bottom earthquakes that occurred during the 1923–2013 period. Based on the slip-distribution data from the Finite-Source Rupture Model Database (SRCMOD) and Okada formulas, the vector fields of co-seismic bottom deformations were calculated. It is shown that, as a rule, the horizontal components of the sloping bottom deformation make an additional and essential contribution to the water displacement and the potential energy of the water-surface elevation that is similar in shape to the bottom surface displacement (the tsunami energy). On the basis of the analyzed relationships between the bottom deformation amplitude, the displaced water volume, tsunami energy, and the earthquake moment magnitude the corresponding regression dependencies were constructed. It is shown that the fraction of the potential energy of an earthquake that is converted into a tsunami increases with the increasing moment magnitude, but even during catastrophic earthquakes it is less than 0.1% of the total earthquake energy.

Contour Data Acquisition System for Electric Vehicle Distance Estimation System

The conventional distance estimation system only uses a constant speed and a constant level of road elevation to estimate the driving range of a vehicle. This technique leads to low prediction accuracy. In this project, a new estimation technique namely the Contour Positioning System (CPS) for an electric vehicle is proposed. The CPS provides a more reliable estimation of the electric vehicle battery energy usage by taking into consideration additional factors such as road elevation and regenerative braking energy. In order to perform the CPS calculation, first and foremost, the elevation profile of the selected destination must be determined. In this paper, the automated technique to extract the elevation profile i.e. latitude, longitude and altitude was determined by using Google Maps and Google Earth. This procedure enables the user to obtain accurate road configuration to enable the driver to compute the amount of energy needed to reach the said destination.

AN EVALUATION OF RANS TURBULENCE CLOSURE MODELS FOR SPILLING BREAKERS

Breaking waves generate turbulence which, along with the bottom stress, undertow, and other mean currents, is capable of suspending and transporting large quantities of sediment. In the present work, open source computational fluid dynamics software is utilised to evaluate four different turbulence models for the application of spilling breakers in the surf zone. The turbulence models are compared against both existing laboratory data and previous numerical models for surface elevation, velocity and turbulent kinetic energy profiles. The results imply that the different models vary in performance for each of these properties and that for incompressible, multiphase flows, it is important to include density explicitly in the turbulence transport equations. Overall, it was found that, out of the models considered, the best one for spilling breakers is the nonlinear k-epsilon model.

Displaced Water Volume, Potential Energy of Initial Elevation, and Tsunami Intensity: Analysis of Recent Tsunami Events

We consider recent ocean-bottom earthquakes for which detailed slip distribution data are available. Using these data and the Okada formulae, we calculate the vector fields of co-seismic bottom deformations, which allow us to determine the displaced water volume and the potential energy of initial elevation of the tsunami source. It is shown that, in the majority of cases, the horizontal components of bottom deformation provide an additional contribution to the displaced water volume and virtually never diminish the contribution of the vertical component. The absolute value of the relative contribution of the horizontal components of bottom deformation to the displaced volume varies from 0.07 to 55 %, on average amounting to 14 %. The displaced volume and the energy of initial elevation (tsunami energy) are examined as functions of the moment magnitude, and the relevant regressions (least-squares fits) are derived. The obtained relationships exhibit good correspondence with the theoretical upper limits that had been obtained under the assumption of uniform slip distribution along a rectangular fault. Tsunami energy calculated on the basis of finite fault model data is compared with the earthquake energy determined from the energy–magnitude relationship by Kanamori. It is shown that tsunami takes from 0.001 to 0.34 % of the earthquake energy, and on average 0.04 %. Finally, we analyze the Soloviev–Imamura tsunami intensity as a function of the following three quantities: (1) the moment magnitude, (2) the decimal logarithm of the absolute value of displaced volume, and (3) the decimal logarithm of the potential energy of initial elevation. The first dependence exhibits rather poor correlation, whereas the second and third dependences demonstrate noticeably higher correlation coefficients. This gives us grounds to suggest considering the displaced volume and the energy of initial elevation as measures of the tsunamigenic potential of an earthquake.

Contribution of horizontal deformation of the seafloor into tsunami generation near the coast of Japan on March 11, 2011

Based on the USGS slip distribution data (Finite Fault Model), the vector field of the seafloor deformation in the source of the tsunami that occurred on March 11, 2011, was calculated. The field of seafloor deformation and distribution of depths in the area of the source were used for reconstruction of the initial elevation of the water surface in the tsunami source. It was found that the contribution of horizontal deformations into the amplitude of the initial elevation, into the displaced water volume, and into the potential energy of the initial elevation is at about 20–25%. Within the framework of the linear theory of long waves, numerical simulation of evolution of the initial elevation was made. The simulation results were compared to the signals recorded by the four deep water stations DART which were the nearest to the source. It was shown that account of the horizontal deformation of the seafloor provides a more precise coincidence between the model and real data. Insignificant differences in arrival times of the model and real signals were interpreted as manifestation of phase dispersion and finite duration for the seafloor deformation to form.

Parameters of Tsunami Source Versus Earthquake Magnitude

This study employs an empirical-analytical approach in combination with Monte-Carlo method to establish relationships between earthquake moment magnitude and upper limits of tsunami source parameters: double-amplitude of vertical bottom deformation, displaced water volume, and potential energy of initial elevation. The approach is based on the Okada solution for a finite rectangular fault and empirical scaling laws for earthquake sources. Results are compared to empirical and theoretical relationships published previously. Parameters of some recent tsunami sources, those for which USGS provides slip distribution data, are considered in light of the established relationships.