Near-field and far-field effects of heating in an over-expanded Mach 2 diamond jet.

2022 ◽  
Author(s):  
Anirudh Lakshmi Narasimha Prasad ◽  
Yousef Saleh ◽  
Prabu Sellappan ◽  
Unnikrishnan Sasidharan Nair ◽  
Farrukh S. Alvi
Keyword(s):  
Near Field ◽  
Far Field ◽  
Field Effects

Near-field and far-field effects in thermal radiation from metallic carbon nanotubes

2007 ◽  
Author(s):  
Andrei M. Nemilentsau ◽  
Gregory Ya. Slepyan ◽  
Sergey A. Maksimenko
Keyword(s):  
Carbon Nanotubes ◽  
Thermal Radiation ◽  
Near Field ◽  
Far Field ◽  
Field Effects

scholarly journals Coupling Methodology for Studying the Far Field Effects of Wave Energy Converter Arrays over a Varying Bathymetry

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2899 ◽  
Author(s):  
Gael Verao Fernandez ◽  
Philip Balitsky ◽  
Vasiliki Stratigaki ◽  
Peter Troch
Keyword(s):  
Numerical Simulations ◽  
Wave Energy ◽  
Near Field ◽  
Coupled Model ◽  
Propagation Model ◽  
Irregular Waves ◽  
Computational Time ◽  
Far Field ◽  
Field Effects ◽  
Numerical Tool

For renewable wave energy to operate at grid scale, large arrays of Wave Energy Converters (WECs) need to be deployed in the ocean. Due to the hydrodynamic interactions between the individual WECs of an array, the overall power absorption and surrounding wave field will be affected, both close to the WECs (near field effects) and at large distances from their location (far field effects). Therefore, it is essential to model both the near field and far field effects of WEC arrays. It is difficult, however, to model both effects using a single numerical model that offers the desired accuracy at a reasonable computational time. The objective of this paper is to present a generic coupling methodology that will allow to model both effects accurately. The presented coupling methodology is exemplified using the mild slope wave propagation model MILDwave and the Boundary Elements Methods (BEM) solver NEMOH. NEMOH is used to model the near field effects while MILDwave is used to model the WEC array far field effects. The information between the two models is transferred using a one-way coupling. The results of the NEMOH-MILDwave coupled model are compared to the results from using only NEMOH for various test cases in uniform water depth. Additionally, the NEMOH-MILDwave coupled model is validated against available experimental wave data for a 9-WEC array. The coupling methodology proves to be a reliable numerical tool as the results demonstrate a difference between the numerical simulations results smaller than 5% and between the numerical simulations results and the experimental data ranging from 3% to 11%. The simulations are subsequently extended for a varying bathymetry, which will affect the far field effects. As a result, our coupled model proves to be a suitable numerical tool for simulating far field effects of WEC arrays for regular and irregular waves over a varying bathymetry.

scholarly journals Irregular Wave Validation of a Coupling Methodology for Numerical Modelling of Near and Far Field Effects of Wave Energy Converter Arrays

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 538 ◽  
Author(s):  
Gael Fernández ◽  
Vasiliki Stratigaki ◽  
Peter Troch
Keyword(s):  
Experimental Data ◽  
Wave Field ◽  
Wave Energy ◽  
Near Field ◽  
Coupled Model ◽  
Propagation Model ◽  
Irregular Waves ◽  
Far Field ◽  
Engineering Research ◽  
Field Effects

Between the Wave Energy Converters (WECs) of a farm, hydrodynamic interactions occur and have an impact on the surrounding wave field, both close to the WECs (“near field” effects) and at large distances from their location (“far field” effects). To simulate this “far field” impact in a fast and accurate way, a generic coupling methodology between hydrodynamic models has been developed by the Coastal Engineering Research Group of Ghent University in Belgium. This coupling methodology has been widely used for regular waves. However, it has not been developed yet for realistic irregular sea states. The objective of this paper is to present a validation of the novel coupling methodology for the test case of irregular waves, which is demonstrated here for coupling between the mild slope wave propagation model, MILDwave, and the ‘Boundary Element Method’-based wave–structure interaction solver, NEMOH. MILDwave is used to model WEC farm “far field” effects, while NEMOH is used to model “near field” effects. The results of the MILDwave-NEMOH coupled model are validated against numerical results from NEMOH, and against the WECwakes experimental data for a single WEC, and for WEC arrays of five and nine WECs. Root Mean Square Error (RMSE) between disturbance coefficient (Kd) values in the entire numerical domain ( R M S E K d , D ) are used for evaluating the performed validation. The R M S E K d , D between results from the MILDwave-NEMOH coupled model and NEMOH is lower than 2.0% for the performed test cases, and between the MILDwave-NEMOH coupled model and the WECwakes experimental data R M S E K d , D remains below 10%. Consequently, the efficiency is demonstrated of the coupling methodology validated here which is used to simulate WEC farm impact on the wave field under the action of irregular waves.

scholarly journals LARGE SCALE EXPERIMENTS ON FARMS OF HEAVING BUOYS TO INVESTIGATE WAKE DIMENSIONS, NEAR-FIELD AND FAR-FIELD EFFECTS

2012 ◽  
Vol 1 (33) ◽  
pp. 71 ◽  
Author(s):  
Vasiliki Stratigaki ◽  
Peter Troch ◽  
Timothy Stallard ◽  
Jens Peter Kofoed ◽  
Michel Benoit ◽  
...  
Keyword(s):  
Wave Energy ◽  
Energy Demand ◽  
Large Scale ◽  
Renewable Energy Sources ◽  
Near Field ◽  
Experimental Studies ◽  
Far Field ◽  
Power Absorption ◽  
Field Effects ◽  
Wave Basin

The shrinking reserves of fossil fuels in combination with the increasing energy demand have enhanced the interest in renewable energy sources, including wave energy. In order to extract a considerable amount of wave power, large numbers of Wave Energy Converters will have to be arranged in arrays or farms using a particular geometrical layout. The operational behaviour of a single device may have a positive or negative effect on the power absorption of the neighbouring WECs in the farm (near-field effects). Moreover, as a result of the interaction between the WECs within a farm, the overall power absorption and the wave climate in the lee of the WECs is modified, which may influence neighbouring farms, other users in the sea or even the coastline (far-field effects). Several numerical studies on large WEC arrays have already been performed, but large scale experimental studies on near-field and far-field wake effects of large WEC arrays are not available in literature. Within the HYDRALAB IV European programme, the research project WECwakes has been introduced to perform large scale experiments in the Shallow Water Wave Basin of DHI, in Denmark, on large arrays of point absorbers for different layout configurations and inter-WEC spacings. The aim is to validate and further develop the applied numerical methods, as well as to optimize the geometrical layout of WEC arrays for real applications.

Far-Field and Near-Field Effects of Marine Aquaculture

2019 ◽  
pp. 197-220 ◽  
Author(s):  
Jenny Weitzman ◽  
Laura Steeves ◽  
Jessica Bradford ◽  
Ramón Filgueira
Keyword(s):  
Near Field ◽  
Far Field ◽  
Marine Aquaculture ◽  
Field Effects

NEAR FIELD AND FAR FIELD EFFECTS IN THE TAGUCHI-OPTIMIZED DESIGN OF AN InP/GaAs-BASED DOUBLE WAFER-FUSED MQW LONG-WAVELENGTH VERTICAL-CAVITY SURFACE-EMITTING LASER

2012 ◽  
Vol 21 (01) ◽  
pp. 1250006 ◽  
Author(s):  
P. S. MENON ◽  
K. KANDIAH ◽  
J. S. MANDEEP ◽  
S. SHAARI ◽  
P. R. APTE
Keyword(s):  
Orthogonal Array ◽  
Near Field ◽  
Fine Tuning ◽  
Design Parameters ◽  
Field Pattern ◽  
Cavity Surface ◽  
Far Field ◽  
Two Dimensional ◽  
Long Wavelength ◽  
Field Effects

Long-wavelength VCSELs (LW-VCSEL) operating in the 1.55 μm wavelength regime offer the advantages of low dispersion and optical loss in fiber optic transmission systems which are crucial in increasing data transmission speed and reducing implementation cost of fiber-to-the-home (FTTH) access networks. LW-VCSELs are attractive light sources because they offer unique features such as low power consumption, narrow beam divergence and ease of fabrication for two-dimensional arrays. This paper compares the near field and far field effects of the numerically investigated LW-VCSEL for various design parameters of the device. The optical intensity profile far from the device surface, in the Fraunhofer region, is important for the optical coupling of the laser with other optical components. The near field pattern is obtained from the structure output whereas the far-field pattern is essentially a two-dimensional fast Fourier Transform (FFT) of the near-field pattern. Design parameters such as the number of wells in the multi-quantum-well (MQW) region, the thickness of the MQW and the effect of using Taguchi's orthogonal array method to optimize the device design parameters on the near/far field patterns are evaluated in this paper. We have successfully increased the peak lasing power from an initial 4.84 mW to 12.38 mW at a bias voltage of 2 V and optical wavelength of 1.55 μm using Taguchi's orthogonal array. As a result of the Taguchi optimization and fine tuning, the device threshold current is found to increase along with a slight decrease in the modulation speed due to increased device widths.

scholarly journals A COUPLING METHODOLOGY TO MODEL NEAR AND FAR FIELD EFFECTS OF STRUCTURES AND ENERGY DEVICES DUE TO WAVE INTERACTION

2018 ◽  
pp. 47
Author(s):  
Vasiliki Stratigaki ◽  
Peter Troch ◽  
David Forehand
Keyword(s):  
Wave Energy ◽  
Hydrodynamic Interaction ◽  
Near Field ◽  
Wave Interaction ◽  
Far Field ◽  
Wave Fields ◽  
Energy Devices ◽  
Field Effects ◽  
Wave Energy Converters ◽  
Coastal Defense

This study focuses on the numerical modeling of wave fields around structures due to their interaction with waves, with the intention to simulate both the resulting near and far field effects. Examples from the wave energy world are employed such as Wave Energy Converters (WECs), fixed or oscillating devices usually arranged in farms, that interact with the incoming waves and extract wave energy from them. As a result of the hydrodynamic interaction between the devices within a farm (so-called near-field effects), the power absorption of the farm is affected. Moreover, wave dissipation has been observed numerically (e.g. Troch et al., 2010) and in scale tests (e.g. Stratigaki et al., 2014; 2015) between the WEC farm location and e.g. the shoreline (so called far-field effects). These wave field changes can affect neighboring sea activities, coastal eco-systems, the coastline and even coastal defense conditions/parameters.

Coupling Methodology for Modelling the Near-Field and Far-Field Effects of a Wave Energy Converter

2017 ◽  
Author(s):  
Philip Balitsky ◽  
Gael Verao Fernandez ◽  
Vasiliki Stratigaki ◽  
Peter Troch
Keyword(s):  
Wave Energy ◽  
Near Field ◽  
Computational Cost ◽  
Propagation Model ◽  
Far Field ◽  
Field Effects ◽  
Wave Energy Converters ◽  
The One ◽  
Geometric Layout ◽  
Low Computational Cost

In order to produce a large amount of electricity at a competitive cost, farms of Wave Energy Converters (WECs) will need to be deployed in the ocean. Due to hydrodynamic interaction between the devices, the geometric layout of the farm will influence the power production and affect the surrounding area around the WECs. Therefore it is essential to model both the near field effects and far field effects of the WEC farm. It is difficult, however, to model both, employing a single numerical model that offers the desired precision at a reasonable computational cost. The objective of this paper is to present a coupling methodology that will allow for the accurate modelling of both phenomena at a reasonably low computational cost. The one-way coupling proposed is between the Boundary Element Method (BEM) solver NEMOH, and the depth-averaged mild-slope wave propagation model, MILDwave. In the presented cases, NEMOH is used to resolve the near field effects whilst MILDwave is used to determine the far field effects.

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