On the Importance of High–Fidelity Numerical Modelling of Ocean Wave Energy Converters under Controlled Conditions

Numerical modelling tools are commonly applied during the development and optimisation of ocean wave energy converters (WECs). Models are available for the hydrodynamic wave structure interaction, as well as the WEC sub–systems, such as the power take–off (PTO) model. Based on the implemented equations, different levels of fidelity are available for the numerical models. Specifically under controlled conditions, with enhance WEC motion, it is assumed that non-linearities are more prominent, re- quiring the use of high–fidelity modelling tools. Based on two different test cases for two different WECs, this paper highlights the importance of high–fidelity numerical modelling of WECs under controlled conditions.

Climate Change Impacts on Wind Waves Generated by Major Tropical Cyclones off the Coast of New Jersey, USA

Coastal areas of State of New Jersey in the Northeastern United States are exposed to extreme wind waves generated by tropical cyclones in the Atlantic Ocean. Past studies suggest that the frequency and intensity of major hurricanes in the Atlantic basin would increase under high greenhouse gas emission scenarios. Furthermore, sea level observations have revealed that the local mean sea level along the coast of New Jersey is rising at a rate higher than that of the global sea level rise. The objective of this study is to quantify the combined influence of sea level rise (SLR) and hurricane climatology change on wave heights induced by major hurricanes off the coast of New Jersey. To this end, a coupled hydrodynamic-wave model is utilized to simulate wind waves for synthetic hurricanes generated for the climate conditions in the historical period of 1980–2000 and future period of 2080–2100 under the RCP8.5 high emission scenario. The synthetic storms are generated by a hurricane model for the climate conditions obtained from four different global climate models. The projections of future wave heights show statistically significant increases in the wave heights induced by major hurricanes. Under the combined effects of hurricane climatology change and a SLR of 1.19 m, the increase in the extreme wave heights 15% in back-bays and shallow waters of the nearshore zone and up to 10% in deeper coastal waters. It is found that SLR alone would result in a significant increase in the hurricane-induced wave heights in the present-day surf zone.

HYDRODYNAMIC WAVE PROCESSES NUMERICAL MODELING IN THE COASTAL RECREATIONAL ZONE OF THE TSIMLYANSK RESERVOIR

This paper presents the results of wave regime hydrophysical characteristics calculations in the area of the accumulative shore of the Tsimlyansky reservoir northwestern part. Wave hydrodynamics model based on 3D mathematical model that includes three Navier-Stokes motion equations, the continuity equations for an incompressible fluid was used. The discretization of the hydrodynamic equations was performed using the pressure correction method. Numerical algorithms and the software package implementing them are used to determine the pressure field, the water medium velocity vector field and to plot the pressure a given section of the reservoir water area. The results of the study can be used in the study of hydrophysical processes, assessment of the hydrodynamic impact on the formation of the coast-line and the bottom relief of large plaintype reservoirs in the Southern Russia.

Development and Application of STORMTOOLS Design Load (SDL) Maps

Under the STORMTOOLS initiative, maps of the impact of sea level rise (SLR) (0 to 12 ft), nuisance flooding (1–10 yr), 25, 50, and 100 yr storms, and hindcasts of the four top ranked tropical storms have been developed for the coastal waters of Rhode Island (RI). Estimates of the design elevations, expressed in terms of the Base Flood Elevation (BFE) and thus incorporating surge and associated wave conditions, have also been developed, including the effects of SLR to facilitate structural design. Finally, Coastal Environmental Risk Index (CERI) maps have been developed to estimate the risk to individual structures and infrastructure. CERI employs the BFE maps in concert with damage curves for residential and commercial structures to make estimates of damage to individual structures. All maps are available via an ArcGIS Hub. The objective of this senior design capstone project was to develop STORMTOOLS Design Load maps (SDL) with a goal of estimating the hydrostatic, hydrodynamic, wave, and debris loading, based on ASCE/SEI 7–16 Minimum Design Standards methods, on residential structures in the RI coastal floodplain. The resulting maps display the unitized loads and thus can be scaled for any structure of interest. The goal of the maps is to provide environmental loads that support the design of structures, and reduce the time and cost required in performing the design and the permitting process, while also improving the accuracy and consistency of the designs. SDL maps were generated for all loads, including the effects of SLR for a test case: the Watch Hill/Misquamicut Beach, Westerly, along the southern RI coast. The Autodesk Professional Robot Structural Analysis software, along with SDL loading, was used to evaluate the designs for selected on-grade and pile-elevated residential structures. Damage curves were generated for each and shown to be consistent with the US Army Corps of Engineers empirical damage curves currently used in CERI.

Evaluation of Hydrodynamic Pressure Distribution in Reservoir of Concrete Gravity Dam under Vertical Vibration Using an Analytical Solution

Fluid-structure interaction causes a hydrodynamic force, which can be exerted to the dam and affects its response. The effect of vertical excitation of ground motion on dynamic behavior of concrete gravity dam is the most important because of the interaction between foundation and reservoir. So, the foundation-reservoir interaction should be taken into account in designing concrete dams. In most studies, the effects of the vertical component of vibration have been ignored. While in vertical vibration, due to the interaction of the reservoir and the foundation, a significant hydrodynamic pressure is produced in the tank, which increases the dam response. In this study, the hydrodynamic pressure wave propagation in the reservoir of a concrete gravity dam caused by interaction with the foundation under vertical vibration is investigated using an analytical method. To achieve an analytical solution, the reservoir is assumed to be rectangular, and a harmonic load is vertically applied on the system from the foundation. Considering the acoustic nature of the reservoir fluid under harmonic vibration, a new method using the separation of variables method has been used for solution of hydrodynamic wave equation. The results show a significant effect of the vertical component of earthquake on the amount of induced pressure distributed in the reservoir, which has been omitted in most previous studies. Obtained results of the proposed model can be extended to more complicated models in terms of different loading and geometrical conditions.

NONLINEAR CONTACT DYNAMICS AND ANTI-SYMMETRY OF CORPUSCULAR-VORTEX-WAVE FORMS OF ELECTROMAGNETIC AND GRAVITATIONAL FIELDS IN THE BACKGROUND MEDIUM OF A COMPLEX EUCLIDEAN SPACE. SPECTRA OF HEATON RADIATION

Based on the hydrodynamic-wave calibration of potentials in Maxwell’s equations and their analogues for the gravitational field, nonlinear equations with respect to the vector potentials of these fields in the background medium of a complex Euclidean space are obtained. The nonlinear contact dynamics of corpuscular-vortex-wave forms of fields and violation of antisymmetry, which leads to the formation of matter and generation of electromagnetic, gravitational, hydrodynamic , acoustic waves separately in real and imaginary half-spaces of complex Euclidean space, are considered. Analytical expressions for the spectra of heaton radiation in a complex Euclidean space are obtained. It is shown that these expressions describe, in particular, the spectrum of solar radiation, collider resonance spectra, the spectrum of microwave background radiation generated by the Oort Cloud, and other spectra in technical, space and geodynamic systems. The fundamental technical failures in the field of controlled thermonuclear fusion and the known catastrophes in nuclear energy and hydropower related to the disregard of corpuscular-wave dualism in macrosystems and the limitations of a purely real part of the complex Euclidean space are analyzed.

Reduction of the VLF Signal Phase Noise Before Earthquakes

In this paper we analyse temporal variations of the phase of a very low frequency (VLF) signal, used for the lower ionosphere monitoring, in periods around four earthquakes (EQs) with magnitude greater than 4. We provide two analyses in time and frequency domains. First, we analyse time evolution of the phase noise. And second, we examine variations of the frequency spectrum using Fast Fourier Transform (FFT) in order to detect hydrodynamic wave excitations and attenuations. This study follows a previous investigation which indicated the noise amplitude reduction, and excitations and attenuations of the hydrodynamic waves less than one hour before the considered EQ events as a new potential ionospheric precursors of earthquakes. We analyse the phase of the ICV VLF transmitter signal emitted in Italy recorded in Serbia in time periods around four earthquakes occurred on 3, 4 and 9 November 2010 which are the most intensive earthquakes analysed in the previous study. The obtained results indicate very similar changes in the noise of phase and amplitude, and show an agreement in recorded acoustic wave excitations. However, properties in the obtained wave attenuation characteristics are different for these two signal parameters.

Historical records of storm frequency on the Shetland Islands (UK) – Preliminary insights from lake sediment cores and coastal wave modelling

<p>Severe storms, their extreme waves and surges pose the greatest natural hazard to the coasts of northwestern Europe, commonly resulting in infrastructural damages and high financial losses. Proxy records of past storminess are important for assessing future risks that may arise from storm surges and assessing whether storm activity has increased in recent decades. High-resolution records of North Atlantic storminess are generally limited to instrumental weather data or historical documentation of the past 50 to 200 years. Since the most destructive and severe storms passing over Europe originate in the North Atlantic, the Shetland Islands serve as a window to cyclogenesis in this region. In our research, we extracted lacustrine sediments of the coastal freshwater lake Loch of Flugarth on Mainland, Shetland Islands, that is separated from the ocean by a low sand and gravel barrier. A series of distinct sand layers intercalated in the otherwise fine-grained, organic-rich lake deposits and examined using particle-size analysis, microfossils, TOC and XRF, may represent storm overwash or aeolian transport mechanisms, both either pointing towards individual storm events or shorter phases of high storm activity. Based on radiocarbon data of some selected layers, the investigated sediment sequence covers ca. 1500 years and a Bayesian age-depth model is being established. In combination with a hydrodynamic wave model based on Delft3D-Flow, we simulate a critical threshold value at which waves may reach the lake to determine the sensitivity of the sedimentary archive. With the inclusion of historical documentation and observations, our multi-methodological approach aims at reaching a better understanding of the recurrence pattern of extreme storm events on the Shetland Islands over the last 1500 years. This implies further insights into the parameters driving extra-tropical storms in the wider region as well as the role and variability of the North Atlantic Oscillation across the targeted time frame.</p>

Coastal extreme sea levels in the Caribbean Sea induced by tropical cyclones

<p>Every year the Caribbean Sea faces the passage of powerful tropical cyclones that generate coastal extreme sea levels with potential strong and hazardous impacts. In this work we simulate the storm surges and wind-waves induced by a set of over 1000 tropical cyclones over the Caribbean Sea that are representative of the present-day climate and that have been extracted from a global database of synthetic hurricanes spanning a 10,000-year period. The atmospheric forcing fields, built from the synthetic tropical cyclones, are used to feed a fully coupled hydrodynamic-wave model with high resolution (~1 km) along the continental and island coasts. Given the large number of events modelled, the outputs allow detailed statistical analyses of the magnitude and mechanisms of coastal extreme sea levels as well as the identification of most exposed areas to both storm surges and large wind-waves.</p>

Coastal risks induced by Mediterranean hurricanes

<p>Medicanes, for Mediterranean hurricanes, are mesoscale cyclones with morphological and physical characteristics similar to tropical cyclones. Although less intense, smaller and rarer than their Atlantic counterparts, Medicanes remain very hazardous events threatening islands and continental coasts within the Mediterranean Sea. The latest strong episode Medicane Ianos (September 2020), resulted in severe damages in Greece and several casualties. This work investigates the oceanic response to these extreme events along the Mediterranean coasts under present-day and future (21 st century) conditions. To this end, a coupled hydrodynamic-wave model is used to simulate both storm surges and wind-waves generation and propagation in the Mediterranean Sea at high resolution (~2 km) along the coastlines. A dataset of thousands of Medicanes synthetically generated from twenty global climate models and two reanalyses is used to derive the atmospheric forcing fields. Regional coastal risks assessment is performed for the present and future climate. We found increased coastal extreme sea levels in line to the reported changes in Medicane activity, with fewer events but of larger intensity projected by late 21 st century.</p>