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.

scholarly journals Enhancing radiative energy transfer through thermal extraction

Nanophotonics ◽  
2016 ◽  
Vol 5 (1) ◽  
pp. 22-30 ◽  
Author(s):  
Yixuan Tan ◽  
Baoan Liu ◽  
Sheng Shen ◽  
Zongfu Yu
Keyword(s):  
Thermal Radiation ◽  
Radiative Heat ◽  
Near Field ◽  
Light Output ◽  
Radiative Energy ◽  
Field Energy ◽  
Far Field ◽  
Thermal Extraction ◽  
Field Radiation ◽  
Boltzmann Law

Abstract Thermal radiation plays an increasingly important role in many emerging energy technologies, such as thermophotovoltaics, passive radiative cooling and wearable cooling clothes [1]. One of the fundamental constraints in thermal radiation is the Stefan-Boltzmann law, which limits the maximum power of far-field radiation to P0 = σT4S, where σ is the Boltzmann constant, S and T are the area and the temperature of the emitter, respectively (Fig. 1a). In order to overcome this limit, it has been shown that near-field radiations could have an energy density that is orders of magnitude greater than the Stefan-Boltzmann law [2-7]. Unfortunately, such near-field radiation transfer is spatially confined and cannot carry radiative heat to the far field. Recently, a new concept of thermal extraction was proposed [8] to enhance far-field thermal emission, which, conceptually, operates on a principle similar to oil immersion lenses and light extraction in light-emitting diodes using solid immersion lens to increase light output [62].Thermal extraction allows a blackbody to radiate more energy to the far field than the apparent limit of the Stefan-Boltzmann law without breaking the second law of thermodynamics.Thermal extraction works by using a specially designed thermal extractor to convert and guide the near-field energy to the far field, as shown in Fig. 1b. The same blackbody as shown in Fig. 1a is placed closely below the thermal extractor with a spacing smaller than the thermal wavelength. The near-field coupling transfers radiative energy with a density greater than σT4. The thermal extractor, made from transparent and high-index or structured materials, does not emit or absorb any radiation. It transforms the near-field energy and sends it toward the far field. As a result, the total amount of far-field radiative heat dissipated by the same blackbody is greatly enhanced above SσT4, where S is the area of the emitter. This paper will review the progress in thermal extraction. It is organized as follows. In Section 1, we will discuss the theory of thermal extraction [8]. In Section 2, we review an experimental implementation based on natural materials as the thermal extractor [8]. Lastly, in Section 3, we review the experiment that uses structured metamaterials as thermal extractors to enhance optical density of states and far-field emission [9].

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

Nanoscale Thermal Radiation Between Coated Spheres

2017 ◽  
Author(s):  
Braden Czapla ◽  
Arvind Narayanaswamy
Keyword(s):  
Radiative Transfer ◽  
Thermal Radiation ◽  
Near Field ◽  
Reflection Coefficients ◽  
Far Field ◽  
Surface Phonon ◽  
Surface Phonon Polariton ◽  
Silver Spheres ◽  
New Formula ◽  
Coated Spheres

In this work, we present a new formula for the near-field thermal radiative transfer between two spheres. The formula is identical for coated or uncoated spheres and captures the effect of the coatings in the effective Mie reflection coefficients of the spheres. We also numerically demonstrate that silica coated silver spheres transition from silver-like conductance in the far-field to surface phonon polariton dominated silica-like behavior in the extreme near-field.

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
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