scholarly journals Modeling and Numerical Simulation of a Buoyancy Controlled Ocean Current Turbine

2021 ◽  
Vol 4 (2) ◽  
pp. 47-58
Author(s):  
Arezoo Hasankhani ◽  
James VanZwieten ◽  
Yufei Tang ◽  
Broc Dunlap ◽  
Alexandra De Luera ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
High Energy ◽  
Ocean Currents ◽  
High Energy Density ◽  
Ocean Current ◽  
Fault Models ◽  
Near Surface ◽  
Renewable Power ◽  
Flow Speeds ◽  
Current Turbine

Increased global renewable power demands and the high energy density of ocean currents have motivated the development of ocean current turbines (OCTs). These compliantly mooring systems will maintain desired near-surface operating depths using variable buoyancy, lifting surface, sub-sea winches, and/or surface buoys. This paper presents a complete numerical simulation of a 700 kW variable buoyancy controlled OCT that includes detailed turbine system, inflow, actuator (i.e., generator and variable buoyancy), sensor, and fault models. Simulation predictions of OCT performance are made for normal, hurricane, and fault scenarios. Results suggest this OCT can operate between depths of 38 m to 329 m for all homogeneous flow speeds between 1.0-2.5 m/s. Fault scenarios show that rotor braking results in a rapid vertical OCT system assent and that blade pitch faults create power fluctuations apparent in the frequency domain. Finally, simulated OCT operations in measured ocean currents (i.e., normal and hurricane conditions) quantify power statistics and system behavior typical and extreme conditions.

Mg-based composites as effective materials for storage and generation of hydrogen for FC applications

2021 ◽  
pp. 53-80
Author(s):  
D. Korablev ◽  
◽  
A. Bezdorozhev ◽  
V. Yartys ◽  
J. Solonin ◽  
...  
Keyword(s):  
Hydrogen Storage ◽  
Hydrogen Generation ◽  
High Energy ◽  
High Energy Density ◽  
Hydrolysis Reaction ◽  
Preparation Technique ◽  
Power Sources ◽  
Safety Issues ◽  
Renewable Power ◽  
Physical And Chemical

Today, hydrogen is considered as an ideal choice for storing and carrying energy produced by renewable power sources since it is renewable, eco-friendly and has a high energy density. However, due to the low hydrogen storage capacity, high cost and safety issues of the conventional storage methods, several challenges need to be resolved to effectively use hydrogen in mobile applications. Solid-state hydrogen storage in atomic form in hydrides is a promising method of storage for this purpose, particularly because a double amount of hydrogen can be produced via hydrolysis reaction of chemically active hydrides. Among the metal hydrides, magnesium hydride (MgH2) is considered to be one of the most attractive candidates. However, the hydrolysis reaction is rapidly hindered by the passivation layer formed on the surface of MgH2. In order to improve MgH2 hydrolysis efficiency various approaches have been applied. This paper reviews recent progress on the modifications of MgH2-based materials by adding different type of additives, including metals, oxides, hydroxides, halides and surfactants. The introduced additives possess different catalytic properties due to their intrinsic physical and chemical characteristics, and therefore can strongly influence the hydrolysis reaction of MgH2. The most promising results were obtained for various salt additives showing that the reaction rate depends mostly on the additive type rather than on concentration. The effect of preparation technique on the hydrolysis of MgH2 – MgCl2 composites was studied in detail. The obtained results indicate that efficient hydrolysis performance can be achieved by ball milling of the freshly synthesized MgH2 with 5 wt.% MgCl2 and 1 wt.% TiC–2TiB2 additives. The combination of the applied approaches exhibited a notable synergistic effect on the hydrogen generation.

Intense Ion-Beam Treatment of Materials

MRS Bulletin ◽  
1996 ◽  
Vol 21 (8) ◽  
pp. 58-62 ◽  
Author(s):  
Harold A. Davis ◽  
Gennady E. Remnev ◽  
Regan W. Stinnett ◽  
Kiyoshi Yatsui
Keyword(s):  
Energy Density ◽  
Surface Treatment ◽  
Laser Processing ◽  
Beam Energy ◽  
Ion Beam ◽  
The United States ◽  
High Energy ◽  
High Energy Density ◽  
X Rays ◽  
Near Surface

Over the past decade, researchers in Japan, Russia, and the United States have been investigating the application of intense-pulsed-ion-beam (IPIB) technology (which has roots in inertial confinement fusion programs) to the surface treatment and coating of materials. The short range (0.1–10 μm) and high-energy density (1–50 J/cm2) of these short-pulsed (t ≥ 1 μs) beams (with ion currents I = 5–50 kA, and energies E = 100–1,000 keV) make them ideal flash-heat sources to rapidly vaporize or melt the near-surface layer of targets similar to the more familiar pulsed laser deposition (PLD) or laser surface treatment. The vaporized material can form coatings on substrates, and surface melting followed by rapid cooling (109 K/s) can form amorphous layers, dissolve precipitates, and form nonequilibrium microstructures.An advantage of this approach over laser processing is that these beams deliver 0.1–10 KJ per pulse to targets at expected overall electrical efficiencies (i.e., the ratio of extracted ion-beam energy to the total energy consumed in generating the beam) of 15–40% (compared to < 1% for the excimer lasers often used for similar applications). Consequently IPIB hardware can be compact and require relatively low capital investment. This opens the promise of environmentally conscious, low-cost, high-throughput manufacturing. Further, efficient beam transport to the target and excellent coupling of incident ion energy to targets are achieved, as opposed to lasers that may have limited coupling to reflective materials or produce reflecting plasmas at high incident fluence. The ion range is adjustable through selection of the ion species and kinetic energy, and the beam energy density can be tailored through control of the beam footprint at the target to melt (1–10 J/cm2) or to vaporize (10–50 J/cm2) the target surface. Beam pulse durations are short (≥ 1 μs) to minimize thermal conduction. Some disadvantages of IPIB processing over laser processing include the need to form and propagate the beams in vacuum, and the need for shielding of x-rays produced by relatively low-level electron current present in IPIB accelerators. Also these beams cannot be as tightly focused onto targets as lasers, making them unsuitable for applications requiring treatment on small spatial scales.

scholarly journals Feedback of mesoscale ocean currents on atmospheric winds in high-resolution coupled models and implications for the forcing of ocean-only models

2017 ◽  
Author(s):  
Rafael Abel ◽  
Claus W. Böning ◽  
Richard J. Greatbatch ◽  
Helene T. Hewitt ◽  
Malcolm J. Roberts
Keyword(s):  
Climate Model ◽  
Global Climate Model ◽  
Surface Wind ◽  
Ocean Currents ◽  
Global Ocean ◽  
Ocean Current ◽  
Western Boundary ◽  
Coupling Coefficients ◽  
Coupled Models ◽  
Near Surface

Abstract. The repercussions of surface ocean currents for the near-surface wind and the air-sea momentum flux are investigated in two versions of a global climate model with eddying ocean. The focus is on the effect of mesoscale ocean current features at scales of less than 150 km, by considering high-pass filtered, monthly-mean model output fields. We find a clear signature of a mesoscale oceanic imprint in the wind fields over the energetic areas of the oceans, particularly along the extensions of the western boundary currents and the Antarctic Circumpolar Current. These areas are characterized by a positive correlation between mesoscale perturbations in the curl of the surface currents and the wind curl. The coupling coefficients are spatially non-uniform and show a pronounced seasonal cycle. The positive feedback of mesoscale current features on the near-surface wind acts in opposition to their damping effect on the wind stress. A tentative incorporation of this feedback in the surface stress formulation of an eddy-permitting global ocean-only model leads to a gain in the kinetic energy of up to 10 %, suggesting a fundamental shortcoming of present ocean model configurations.

Numerical Simulation of an Experimental Ocean Current Turbine

2013 ◽  
Vol 38 (1) ◽  
pp. 131-143 ◽  
Author(s):  
James H. VanZwieten ◽  
Nicolas Vanrietvelde ◽  
Basil L. Hacker
Keyword(s):  
Numerical Simulation ◽  
Ocean Current ◽  
Current Turbine

SURVIVAL OF J/Ψ IN HADRONIC MATTER AT HIGH ENERGY DENSITY?

1989 ◽  
Vol 04 (17) ◽  
pp. 1627-1634 ◽  
Author(s):  
D. NEUBAUER ◽  
K. SAILER ◽  
B. MÜLLER ◽  
H. STÖCKER ◽  
W. GREINER
Keyword(s):  
Numerical Simulation ◽  
Cross Section ◽  
Major Part ◽  
Simulation Modelling ◽  
High Energy ◽  
Hadronic Matter ◽  
High Energy Density ◽  
Collision Rate ◽  
Thermodynamical Equilibrium ◽  
Final State

The collision rate of massive strings representing J/Ψ mesons has been determined by numerical simulation, modelling the surrounding hadronic matter as an ideal string gas in thermodynamical equilibrium. The survival time of the J/Ψ string tends to zero at the Hagedorn temperature. Whether the final state J/Ψ-nucleon scattering accounts for a major part of the observed J/Ψ suppression, depends on the value of the J/Ψ-nucleon cross section.

Numerical Analysis of Hydrodynamic Performance of FX-83-W Hydrofoil Current Turbine

2017 ◽  
Author(s):  
Yuchen Shang ◽  
Nikolaos I. Xiros
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Open Water ◽  
Hydrodynamic Performance ◽  
Ocean Current ◽  
Thrust Coefficient ◽  
Cfd Method ◽  
Three Dimensional Coordinate ◽  
Current Turbine

Ocean current flow characteristics are relatively stable and predictable, current turbine absorbs the energy of the ocean currents by the blades with a relative stable and lower angular velocity which indicates the capacity of current turbine greater than the onshore wind turbine. In this paper, the CFD method is utilized to calculate and analyze the working principle of FX-83-W current turbine. The three-dimensional coordinate of FX-83-W Hydrofoil blade surface have been calculated by MATLAB code, and 3D model has been established in Gambit. The basic control equations of CFD and its numerical solution are described, Reynolds Averaged N-S equations is used, and the realizable k-e turbulence model is introduced to solve the Reynolds stress in the RANS equation. The numerical algorithm is the finite volume method (FVM), and the numerical simulation of CFD is used to study the open water performance, leading to thrust coefficient KT and torque coefficient KQ of FX-83-W Hydrofoil. The hydrodynamic thrust and hydrodynamic power of the ocean current turbine under different sea conditions have been obtained by numerical simulation.

scholarly journals Baroclinic Effect on Modeling Deep Flow in Brown Passage, BC, Canada

2018 ◽  
Vol 6 (4) ◽  
pp. 117 ◽  
Author(s):  
Yuehua Lin ◽  
David Fissel ◽  
Todd Mudge ◽  
Keath Borg
Keyword(s):  
Transport Model ◽  
Important Change ◽  
Ocean Currents ◽  
Internal Tides ◽  
Ocean Current ◽  
Near Surface ◽  
The Pacific ◽  
Wind Driven Currents ◽  
Baroclinic Effect ◽  
Good Agreement

Brown Passage is a deep (up to 200 m) ocean channel connecting the western offshore waters of Hecate Strait and Dixon Entrance on the Pacific continental shelf with the eastern inland waters of Chatham Sound in Northern British Columbia, Canada. A high-resolution 3D finite difference hydrodynamic model, COastal CIRculation and SEDiment transport Model (COCIRM-SED), was developed in 2010 and 2013 to determine the tidal and wind-driven currents of this area. The barotropic model results for ocean currents were found to be in reasonably good agreement with the historical ocean current observations at near-surface and middle depth available for Brown Passage. Operated from October 2014 to April 2015, the first modern oceanographic measurement program in Brown Passage found surprisingly strong near-bottom currents (the 99th percentile current speed reaches 53 cm/s at 196 m). As a result, the COCIRM-SED model was modified and rerun, with the most important change incorporating water density/salinity fields as modeled variables. This change led to considerable improvements in the ability of the model to generate episodes of relatively strong currents in the bottom layers. The bottom intensification in ocean currents in Brown Passage is shown to be due to semi-diurnal internal tides, which were not previously included in the barotropic version of the 3D model. This finding for the near-bottom flow from the qualitative modeling study is important for applications of the potential sediment deposition and resuspension studies.

Numerical Investigation of an Experimental Ocean Current Turbine Based on Blade Element Momentum Theory (BEM)

2021 ◽  
Author(s):  
S. Sadeqi ◽  
S. Rouhi ◽  
N. Xiros ◽  
E. Aktosun ◽  
J. VanZwieten ◽  
...  
Keyword(s):  
Performance Analysis ◽  
Ocean Currents ◽  
Ocean Current ◽  
Test Model ◽  
Small Current ◽  
Power Estimate ◽  
Blade Element Momentum Theory ◽  
Momentum Theory ◽  
Current Turbine ◽  
Blade Element

Abstract Ocean currents are one of the alternative sources of green, sustainable, and renewable energy that could generate low-cost electric power without any pollution due to the burning of fossil fuels. Due to the density of the water, ocean currents can produce a significant amount of energy even with a very small current velocity field. In this study, a comprehensive performance analysis of 3-blade horizontal-axis Ocean Current Turbine (OCT) is shown to achieve optimal rpm (revolutions per minute) to match environmental conditions in order to harvest the maximum possible energy from OCT in ocean currents. Our approach is to use Blade Element Momentum (BEM) theory in order to estimate hydrodynamic loads for the turbine; specifically, the design of the OCT blades is based on a FX77-W121 type airfoil. We use JavaFoil to analyze and determine hydrodynamic lift and drag coefficients with respect different angles of attack for the hydrofoil profiles in seawater. After validation of blade design characteristics and obtaining the local coefficients of each hydrofoil cross-sections, we transfer them to our in-house-developed Blade Element Momentum Theory (BEM) code in order to achieve the estimation of performance analysis of the OCT in order to get maximum power and ideal torque and thrust. This performance analysis with BEM model of the OCT is an important step for further analysis due to having different incoming flow speeds in actual time-varying sea conditions. Indeed, the OCT will encounter different incoming ocean current speeds during operation. Therefore, this approach is used to get an accurate brake power estimate of the OCT in different operational current speeds. In addition, this performance analysis of the OCT is going to be utilized in designing and developing a test model for the physical towing tank experiment for later investigation.

Beamweldfoam: Numerical Simulation of High Energy Density Fusion and Vapourisation-Inducing Processes

2021 ◽  
Author(s):  
Thomas Flint ◽  
Gowthaman Parivendhan ◽  
Alojz Ivankovic ◽  
Mike Smith ◽  
Philip Cardiff
Keyword(s):  
Numerical Simulation ◽  
Energy Density ◽  
High Energy ◽  
High Energy Density
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