DOI： 10.1021/acscentsci.8b00802

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier Ltd  

To use and understand the large-scale natural convection in the building and systems, heat transfer analysis of the natural convection with radiation is important. The radiation effect is influenced by concentration of the participating media in the considered system. In this study, an effects of concentration of participating media on turbulent natural convection inside a cubic cavity were investigated. The turbulence effect was modeled by large eddy simulation. Further, the radiative heat transfer was calculated by the radiation element method using the ray emission model. In addition, the gas radiation was modeled by the full-spectrum k-distribution method. By varying the partial pressures of H2O and CO2, the effect of the participating media were evaluated. From the calculation, gas radiation effects affected the flow instability and restrained the temperature stratification when the concentration of the participating media was higher. However, the convective heat transfer have not been affected by the significant flow instability by the radiation effects.

DOI： 10.1016/j.applthermaleng.2017.11.135

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Taylor and Francis Ltd.  

We performed a direct numerical simulation (DNS) of the turbulent natural convection between two parallel plates at a Rayleigh number of Ra = 8.0 × 106, focusing on the turbulent natural convection affected by radiation in an optically thick fluid (τ ≥ 10). When the effects of the radiation were considered, the flow structure and temperature distribution in the channel changed as the optical thickness of the fluid increased. The effects of the radiation on the turbulent natural convection were clearly explained by the turbulence statistics from the DNS results.

DOI： 10.1080/10407782.2017.1412713

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OPTICAL SOC AMER  

Metasurfaces with metal-insulator-metal structures have attracted significant attention because of their high optical performance. Their spectral emissivity/absorptivity can be modulated with geometrically controlled electromagnetic resonances. However, practical fabrication of these materials in the meter scale remains a challenge. In the present study, an aluminum-and ceria-based metasurface that exhibits nearly perfect emission/absorption in the infrared region was designed. Furthermore, we succeeded in fabricating the proposed metasurface in the meter scale via photolithography and wet etching. This study enhances understanding of underlying resonance mechanisms with electromagnetic simulations and equivalent circuit model, and will facilitate the experimental design of high-efficiency largearea metasurfaces. (C) 2017 Optical Society of America

DOI： 10.1364/OME.7.000618

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

The purpose of this study is to clarify the optical characteristics of a Tungsten SiO2-based film-couple metamaterial with a fishnet-shaped grating, and we aim to show that this structure could potentially be used a solar selective absorber for a solar thermophotovoltaic system. The proposed film-coupled metamateris absorber combined with a fishnet-shaped grating shows significant enhancement in its absorption in the spectral region compared with a flat Tungsten surface, and it keeps its spectral emission low in the infrare region, thereby reducing radiative heat loss. The underlying mechanisms of the proposed absorber are discusse through a 3D full-wave electromagnetic simulation, the results of which are compared with that of theoretic equations. Furthermore, its spectral absorption under oblique incident light at the transverse magnetic am transverse electric waves is scrutinized. The underlying absorption mechanisms and relations between eac optical resonance are discussed in this paper and will prove to be fundamental not only in the design of selective absorbers but also in other wavelength-selective thermal radiation controlling devices.

DOI： 10.1016/j.optcom.2016.10.044

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

The turbulence structure, boundary layer, and heat transfer of turbulent natural convection, including radiation effects inside the cubic cavity, were investigated in this study. Large eddy simulation was conducted, and Vreman model was adopted for the dynamic subgrid-scale model. To calculate the radiative heat flux efficiently, a coupled calculation method, using the radiation element method by ray emission model, was constructed. To separate the radiation effects of the gas and surface radiations, four calculation conditions have been analyzed; non-radiation, gas radiation, surface radiation, and combined radiation. Observing the vortices structure using the Q value revealed that the surface radiation effect was more dominant for the flow instability than the gas radiation effect. An evaluation of the boundary layers for both the gas and surface radiation effects showed that the flow circulation inside the cubic cavity was enhanced. The surface radiation was dominant in the generation of the shear stress by the turbulent flow. The total heat transfer, which includes the convective and radiative heat transfers, have been investigated. The surface radiation affected on the radiative heat transfer significantly as compared to the gas radiation. The radiation effects changed the radiative heat transfers, while the convective heat transfers of all the calculation conditions were similar. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijheatmasstransfer.2016.08.059

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

We numerically investigate a solar-selective absorber with tungsten core-shell nano particle arrays embedded in an SiO2 layer. The 3D full-wave finite-difference time-domain (FDTD) simulations are performed to investigate the geometric effects of different types of solar-selective absorbers. Consequently, broadband light absorption was achieved with either a tungsten nanoparticle array or a tungsten core-shell nanoparticle array because of the strong electric field enhancement in the gap between the core nanoparticles. The solar performance of the proposed structure is shown for high-efficiency solar light absorption. This study enhances understanding of the light absorption mechanism of metallic nanoparticle/dielectric composite and facilitates the design of high-efficiency solar-selective absorbers. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jqsrt.2016.08.005

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER INST AERONAUTICS ASTRONAUTICS  

Due to the interference effect, the reflectance and transmittance of an arbitrary linearly polarized wave cannot be fully described by the reflectance and transmittance of transverse electric and transverse magnetic waves. In this work, the polarization dependence of reflectance and transmittance for anisotropic metamaterials is examined. The explicit mathematical relationship between the Fresnel coefficients and the reflectance (or transmittance) for a given polarization angle is derived. A method is presented that can be used to obtain the reflectance (or transmittance) for any polarization angle from three other polarizations. Several different anisotropic metamaterials are numerically investigated with the finite-difference time-domain technique to elucidate the polarization dependence of reflectance or transmittance. The reflectance and transmittance obtained from the three-polarization-angle method are in agreement with those from the rigorous numerical simulation.

DOI： 10.2514/1.T4587

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

This work deals with the spectral radiative properties of metamaterials made of a 2D metallic pattern on a dielectric thin film that separates the top periodic structure from a metal ground plane. Two distinct patterns are considered: one consists of disconnected double-rectangle gold pattern and the other is made of L-shape pattern. Both structures exhibit dual-band emission or absorption peaks in the infrared region. Unlike the disconnected rectangular pattern for which the normal emittance is independent of the polarization angle, the L-shape structure shows strong polarization dependent due to near-field coupling. The electromagnetic fields at the resonant frequencies are analyzed using the finite-difference time-domain technique to elucidate the physical mechanisms accounting for the different behaviors. For both structures, the resonance mechanisms can be explained by magnetic polaritons. Inductor-capacitor circuit models are developed to quantitatively predict the resonance frequencies. This work helps the understanding of polarization dependence in metamaterials and may facilitate their applications in biosensing and infrared spectroscopic system. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jqsrt.2014.11.018

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

This study describes the flow and thermal field of a two-tower fluidized receiver, aimed to be incorporated into a beam-down reflector system. An experimental visualization and numerical simulation were made to accumulate phenomenological knowledge, in order to complete the design of a demonstration model. Visualization of the cold particle bed with no irradiation revealed that global circulation occurs between the two towers by the aeration with different line velocities. The numerical simulation revealed that this global circulation enhances the transport of sensible heat from the irradiated layer in the high pressure tower to the low pressure tower. The global circulation in the two-tower fluidized receiver has the potential to be extended for use in a thermal receiver and direct storage system. Unexpectedly, local circulations occur on the high and low pressure sides, and are stronger than the global circulation. These local circulations contribute to the thermal mixing in each tower. The bottom distributor on the low pressure side can cause an uprising flow which leads to the local circulation. The design of the distributor is suggested to be elaborated based on these findings. (C) 2015 The Authors. Published by Elsevier Ltd.

DOI： 10.1016/j.egypro.2015.03.057

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japan Institute of Energy  

This study proposes a t wo-tower t ype fluidized receiver for receiving concentrated s olar light at high temperatures is proposed. This fluidized receiver is coupled with the Miyazaki beam-down reflector system. The visualization and the numerical simulation was made for the laboratory model to show the fluid-dynamics and the heat transport as well as to elaborate the existing demonstration model. The experimental visualization of the cold model demonstrated that in each tower, the particles are moved by the aerated organized flow. The numerical simulation was made using the thermal input cited from the 5.0kWth sun simulator. The numerical simulation demonstrated that the inner particles are heated above 950 °C after 3.0 minutes of the aeration start time. The increase in temperature is caused by the intrusion of the heated particles from the high-pressure side tower to the low-pressure side tower. It is thus suggested that collective circulation occurs between high- and low-pressure side towers and this can be utilized for a direct thermal storage system.

DOI： 10.3775/jie.94.1323

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

Metamaterial thermal emitters and absorbers have been widely studied for different geometric patterns by exciting a variety of electromagnetic resonances. A resistor-inductor-capacitor (RLC) circuit model is developed to describe the magnetic resonances (i.e. magnetic polaritons) inside the structures. The RLC circuit model allows the prediction of not only the resonance frequency, but also the full width at half maximum and quality factor for various geometric patterns. The parameters predicted by the RLC model are compared with the finite-difference time-domain simulation. The magnetic field distribution and the power dissipation density profile are also used to justify the RLC circuit model. The geometric effects on the resonance characteristics are elucidated in the wire (or strip), cross, and square patterned metamaterial in the infrared region. This study will facilitate the design of metamaterial absorbers and emitters based on magnetic polaritons. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jqsrt.2014.07.024

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

The purpose of this study is to computationally design a wide-angle cermet-based solar selective absorber for high temperature applications by using a characteristic matrix method and a genetic algorithm. The present study investigates a solar selective absorber with tungsten-silica (W-SiO2) cermet. Multilayer structures of 1, 2, 3, and 4 layers and a wide range of metal volume fractions are optimized. The predicted radiative properties show good solar performance, i.e., thermal emittances, especially beyond 2 mu m, are quite low, in contrast, solar absorptance levels are successfully high with wide angular range, so that solar photons are effectively absorbed and infrared radiative heat loss can be decreased. (C) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jqsrt.2013.03.004

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（研究会，シンポジウム資料等）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

DOI： 10.1016/j.jqsrt.2013.06.012

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

This study proposes a novel fluidized receiver for absorbing concentrated solar light at high temperatures. Previously, a tubular receiver and a volumetric receiver were developed to make high-temperature air for a solar gas turbine system. The aim was to combine these elements with a tower reflector; however, it was challenging to install these heavy receivers on the top of the tower. Currently, a fluidized receiver prototype is tested by a 3 kWh solar simulator in preparation for a field test at the Miyazaki beam-down reflector system. The fluid dynamics of the prototype receiver is numerically investigated. The currently treated receiver is an inner-circulating fluidized bed spouted by concentric gas streams with high and low velocities in the center and outer annulus, respectively. The draft tube is submerged in the particles to organize particle circulation. Concentrated light irradiates the particles through a quartz window at the top of the receiver container. Such a fluidized bed was first adopted by Kodama et al. for thermochemical reactions; however, it is currently pursued for its potential as a high-temperature receiver aimed at concentrated solar power generation. Experiments of the prototype receiver (inner diameter = 45 mm) demonstrated that the inner particles are heated to a temperature greater than 900 degrees C and that an increase of the central gas velocity removes the excess temperature near the particle bed surface. A numerical computation suggests that the large-scale circulation of particles leads to the activation of thermal mixing. The currently proposed receiver is thus expected to attenuate re-radiation losses likely to occur in a conventional volumetric porous receiver. The scale-up of the receiver is being considered by the numerical computation for a field test in the Miyazaki 100 kWh beam-down reflector system. (C) 2013 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

DOI： 10.1016/j.egypro.2014.03.048

Web of Science

researchmap

掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Begellhouse  

DOI： 10.1615/ihtc15.rad.009012

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

The purpose of this study is to clarify the radiation effects on mixed turbulent convection in a horizontal channel. The present study provides turbulence statistics using direct numerical simulation (DNS) in an optically thin medium. When the radiation effect is considered, the flow structure and the temperature distribution in the channel change with an increase in the optical thickness of the fluid. The radiation effect changes the distributions of the temperature fluctuation intensity and the turbulent heat flux. These radiation effects on mixed convection can be clearly explained by the turbulence statistics obtained from the DNS results. (C) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijheatmasstransfer.2012.01.006

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ASME-AMER SOC MECHANICAL ENG  

The near-wall turbulent heat transport of the three orthogonal directions was directly solved for the Prandtl numbers ranging from 0.025 to 5.0 to validate the algebraic models of the turbulent heat flux. Two kinds of thermal situations were considered in the low Reynolds number turbulent flow: (a) the case with a uniform heat flux in the spanwise direction (UHF) and (b) the case with the mean spanwise temperature gradient (STG). Among the turbulent heat flux models tested, the model of Rogers preferably predicted over the treated range of the Prandtl numbers, but it failed to reproduce the low Prandtl number effects very accurately. This paper revealed that the coefficient of the Rotta model can be modified to include the low Prandtl number effects by means of the correlation between the exact coefficient suggested by DNS and the Prandtl number. [DOI: 10.1115/1.4005077]

DOI： 10.1115/1.4005077

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS INC  

A newly developed electric furnace was used to pyrolyze benzene, methane, or acetylene diluted by a nonreactive gas, and the carbon aggregates were separated from the hydrogen-rich gases. The temperature was changed up to 2200K for various levels of initial concentration of hydrocarbon and residence time, and how the experimental parameters affected the mean diameter of carbon aggregates was examined. The temperature increase in experiments led to reduction of the mean diameter of the carbon aggregates, whereas increase in the initial concentration of hydrocarbon or the residence time resulted in slightly lifting it. The mean diameter removed of temperature effects correlated well with the initial carbon atom mol concentration of hydrocarbon, N-C, and this parameter was used to develop the experimental equations. This article presents three kinds of experimental equations, and the prediction accuracy was confirmed to be improved when accounting for increasing the experimental parameters.

DOI： 10.1080/00102202.2012.691582

Web of Science

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1299/kikaib.78.607

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN SOC MECHANICAL ENGINEERS  

Heat transfer and fluid flow in a single-rib mounting channel were investigated by directly solving Navier-Stokes and energy equations. The flow and thermal fields were considered to be fully developed at the inlet of the channel, and the simulation was made for spatial advancement of turbulent heat transfer. The Reynolds number based on the friction velocity at the inlet and the channel half width was 150. The Prandtl number was 0.71. The budgets for turbulent heat fluxes and temperature variance at various sections were presented and were investigated, which would be useful for testing and developing turbulence models. Near a circular vortex in front of the rib, pressure diffusion terms made an important contribution. Remarkable production terms were generated near a reattachment point. Production and dissipation terms were not dominant in front of and above the rib, and a time scale ratio exceeded 2.0 in the region.

DOI： 10.1299/jtst.7.120

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER INST PHYSICS  

Direct numerical simulation was performed for the spatially advancing turbulent flow in a two-dimensional curved channel. The fully developed turbulence was introduced into the curved channel through a straight part, and observation was made for how the near-wall turbulence advanced along curved walls. The frictional Reynolds number, Re(tau 0), was fixed at 150, whereas the radius ratio of the curved channel, alpha, was changed at three steps; 0.8, 0.92, and 0.975. Five computational tests were performed, which include simulations with changing the spanwise length of the channel or the grid arrangement. The maximum number of grid points was 43,610,112 (=936 x 91 x 512) used in the case of alpha = 0.92. Numerical results for the curved flow were nearly free from the grid arrangement or the spanwise length of the channel, and changes of the mean velocity qualitatively agreed with the experiment by Kobayashi [Trans. Jpn. Soc. Mech. Eng., Ser. B 57, 4064 (1991)], which both supported credibility of the simulation. The spanwise pre-multiplied power spectrum and the spanwise two-point correlation captured the peaks corresponding to the micro-scale structures near the straight wall, which continuously grew along the concave wall and advanced to exhibit the wave length of organized flows. Therefore, the micro-scale structures such as quasi-stream vortices and the ejection near the outer wall of the straight channel were suggested to trigger the onset of initial seeds of the organized structure, which grew into the large scale vortices expanding almost over the channel width.(C) 2011 American Institute of Physics. [doi: 10.1063/1.3584126]

DOI： 10.1063/1.3584126

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS INC  

Direct numerical simulation was performed for the spatially advancing turbulent flow and heat transfer in a two-dimensional curved channel equating the radius ratio to 0.92 or 0.8. The frictional Reynolds number was fixed at 150, whereas the Prandtl number was set at 0.71. According to the numerical result, the remarkable enhancement of heat transfer occurred on the outer wall, suggesting the organized vortex activated the heat transfer. The budgets of Reynolds stresses clarified that the onset and growth of the organized flow was assisted by the direct energy transfer from the mean flow.

DOI： 10.1080/10407782.2011.588562

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPRINGER  

DOI： 10.1007/978-94-007-2482-2_49

Web of Science

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1299/kikaib.77.2170

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN SOC MECHANICAL ENGINEERS  

Thermal radiation in a turbulent natural convection plays an important role in a wide area of engineering and nature. The purposes of this study are to investigate the effects of turbulent fluctuation on radiative heat transfer, and to evaluate radiative heat transfer models applied to turbulent natural convection. The present radiative heat transfer analysis of a turbulent natural convection using direct numerical simulation (DNS) provides a useful fundamental data for the complete coupling simulation in the future.

DOI： 10.1299/jtst.6.449

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ASME-AMER SOC MECHANICAL ENG  

The purpose of this paper is to consider a possibility of the independent column approximation for solving the radiative heat fluxes in a 3D turbulent channel flow. This simulation method is the simplest extension of the plane-parallel radiative heat transfer. The test case of the temperature profile was obtained from the direct numerical simulation. We demonstrate the comparison between the 3D radiative transfer simulation and the independent column approximation with an inhomogeneous temperature field and optical properties. The above mentioned results show the trivial discrepancies between the 3D simulation and the independent column approximation. The required processing time for the independent column approximation is much faster than the 3D radiative transfer simulation due to the simple algorithm. Although the independent column simulation is restricted to simple configurations such as channel flow in this paper, wide application areas are expected due to the computational efficiency.

DOI： 10.1115/1.4000240

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Direct numerical simulation was performed for a spatially advancing turbulent flow and heat transfer in a two-dimensional curved channel, where one wall was heated to a constant temperature and the other wall was cooled to a different constant temperature. In the simulation, fully developed flow and temperature from the straight-channel driver was passed through the inlet of the curved-channel domain. The frictional Reynolds number was assigned 150, and the Prandtl number was given 0.71. Since the flow field was examined in the previous paper, the thermal features are mainly targeted in this paper. The turbulent heat flux showed trends consistent with a growing process of large-scale vortices. In the curved part, the wall-normal component of the turbulent heat flux was twice as large as the counterpart in the straight part, suggesting active heat transport of large-scale vortices. In the inner side of the same section, temperature fluctuation was abnormally large compared with the modest fluctuation of the wall-normal velocity. This was caused by the combined effect of the large-scale motion of the vortices and the wide variation of the mean temperature
in such a temperature distribution, large-scale ejection of the hot fluid near the outer wall, which is transported into the near inner-wall region, should have a large impact on the thermal boundary layer near the inner wall. Wave number decomposition was conducted for various statistics, which showed that the contribution of the large-scale vortex to the total turbulent heat flux normal to the wall reached roughly 80% inside the channel 135° downstream from the curved-channel inlet. © 2009 Wiley Periodicals, Inc.

DOI： 10.1002/htj.20275

Scopus

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1299/kikaib.76.771_1681

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS INC  

This article deals with the implementation of the radiation element method (REM) with the lattice Boltzmann method (LBM) to solve a combined mode transient conduction-radiation problem. Radiative information computed using the REM is provided to the LBM solver. The planar conducting-radiating participating medium is contained between diffuse gray boundaries, and the system may contain a volumetric heat generation source. Temperature and heat flux distributions in the medium are studied for different values of parameters such as the extinction coefficient, the scattering albedo, the conduction-radiation parameter, the emissivity of the boundaries, and the heat generation rate. To check the accuracy of the results, the problem is also solved using the finite-volume method (FVM) in conjunction with the LBM. In this case, the data for radiation field are calculated using the FVM. The REM has been found to be compatible with the LBM, and in all the cases, results of the LBM-REM and the LBM-FVM have been found to provide an excellent comparison.

DOI： 10.1080/10407780903583008

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN SOC MECHANICAL ENGINEERS  

Heat transfer and fluid flow in a single-rib mounting channel were investigated by directly solving Navier-Stokes and energy equations. Flow and thermal fields were considered to be fully developed at the inlet of the channel, and the simulation was made for spatial advancement of turbulent heat transfer. Keeping the frictional Reynolds number, Re-tau 0, at 150, the rib height ratio was changed in four steps from H/delta = 0.05 to H/delta = 0.4. Computational results were confirmed to be nearly independent of grid meshes. In addition, numerical accuracy was confirmed through close agreement between computed mean pressure and the experiment by Yao et al. (1995). The numerical results revealed that the highest value of the mean Nusslet number was as large as 1.3 times the smooth surface consuming the same pumping power, and the local enhancement of heat transfer was correlated with the turbulence increase near the rib front and the reattachment point. According to the Reynolds stress budgets for H/delta = 0.2, there were mechanisms to induce powerful fluctuations: (1) Streamwise fluctuation was increased through production by flow deceleration in the upstream of the rib; (2) Redistribution to wall-normal and spanwise fluctuations was fortified by the fluid splattering to the rib front. Therefore, excellent performance of heat transfer was concluded to occur due to flow structures, which induce the strong disturbance near the rib front triggering smooth transition of the separated shear layer.

DOI： 10.1299/jtst.5.135

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS INC  

The purpose of this study is to develop the radiation element method by ray emission method (REM2) code appropriate for coupling with the bioheat transfer equation, and to clarify the photothermal effect of various parameters inside biological tissues. First, the REM2, which involves the air-tissue interface effect, is validated with the existing literature. In order to clarify the effects of optical and thermophysical properties of biological tissues, a one-dimensional tissue model of CW light transport and bioheat transfer is employed. The present study provides nondimensional results, which are obtained by varying refractive index, extinction coefficient, scattering albedo, blood perfusion parameter, and conduction-radiation parameter, show valuable guidance for understanding the coupled light and bioheat transport in tissues.

DOI： 10.1080/10407782.2010.516698

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

In this study, a combinatorial optimization methodology has been presented for determining the optimal number and location of equally powered heaters over some parts of the boundary, called the heater surface, to satisfy the desired heat flux and temperature profiles over the design surface while keeping the total heaters power constant but floating the number of heaters. In a typical enclosure, candidate locations were numerous for placing the heaters. The optimal number and location could be found by checking among all the possible combinations of heater power ranges and locations on the heater surface. The possibility of checking only a small portion of the total search space was increasingly desirable for finding an overall optimal solution. Micro-genetic algorithm was a candidate method which displayed a significant potential in achieving that task. Micro-genetic algorithm was used to minimize an objective function which was expressed by the sum of square errors between estimated and desired heat fluxes on the design surface. Radiation element method by ray emission model (REM(2)) Was used to calculate the radiative heat flux on the design surface. It enabled us to handle the effects of specular surfaces and blockage radiation due to enclosure geometry. The capabilities of this methodology were demonstrated by finding the optimal number and position of heaters in two irregular enclosures. The effects of refractory surface characteristics (i.e., diffuse and/or specular) on the optimal solution have been studied in detail. The results show that the refractory surface characteristics have profound effects on the optimal number and location of heaters. (C) 2008 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.applthermaleng.2008.05.025

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN SOC MECHANICAL ENGINEERS  

The objective of this study is to develop a new simulator for laser therapy. In order to minimize undesired effects on the laser therapy, it is important to precisely predict for heat and photon transport inside a biological tissue. In the present study, the photon transport is solved with the Radiation Element Method by Ray Emission Model (REM2), and then coupled with bioheat transfer equation. The dimensionless results become valuable guidance for developing a laser therapy system.

DOI： 10.1299/jtst.4.314

Web of Science

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1299/kikaib.75.754_1336

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

Simplifications of the model for nongray radiative heat transfer analysis in participating media comprised of polydisperse water droplets are presented. Databases of the radiative properties for a water droplet over a wide range of wavelengths and diameters are constructed using rigorous Mie theory. The accuracy of the radiative properties obtained from the database interpolation is validated by comparing them with those obtained from the Mie calculations. The radiative properties of polydisperse water droplets are compared with those of monodisperse water droplets with equivalent mean diameters. Nongray radiative heat transfer in the anisotropic scattering fog layer, including direct and diffuse solar irradiations and infrared sky flux, is analyzed using REM2. The radiative heat fluxes within the fog layer containing polydisperse water droplets are compared with those in the layer containing monodisperse water droplets. Through numerical simulation of the radiative heat transfer, polydisperse water droplets can be approximated by using the Sauter diameter, a technique that can be useful in several research fields, such as engineering and atmospheric science. Although this approximation is valid in the case of pure radiative transfer problems, the Sauter diameter is reconfirmed to be the appropriate diameter for approximating problems in radiative heat transfer, although volume-length mean diameter shows better accordance in some cases. The CPU time for nongray radiative heat transfer analysis with a fog model is evaluated. It is proved that the CPU time is decreased by using the databases and the approximation method for polydisperse particulate media. (C) 2007 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jqsrt.2007.05.006

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN SOC MECHANICAL ENGINEERS  

This study presents an optimization methodology for finding the heaters setting that produce a desired heat flux and temperature distribution over a region of the enclosure surface, called the design surface. Radiation element method by ray emission model (REM2) was used to calculate the radiative heat flux on the design surface, which enable us to handle reflecting surfaces. Micro-genetic algorithm was used to minimize an objective function, which was expressed by the sum of square error between estimated and desired heat fluxes on the design surface. The novel features of this methodology were demonstrated by finding the optimal heaters setting of a three dimensional enclosure for three aspect ratio. The effects of refractory properties have been studied as well.

DOI： 10.1299/jtst.3.179

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS INC  

A new algorithm, the discrete ordinates radiation element method (DOREM), for modeling radiative heat transfer in inhomogeneous three-dimensional participating media is described. The DOREM uses advantages of the both the radiation element method (REM) and the discrete ordinates method. Benchmark comparisons are conducted against several radiation models. The DOREM successfully implements radiative heat transfer simulations precisely, since false scattering never occurs. The DOREM has advantages of computational speed against Monte Carlo, and the CPU time and the memory size of the DOREM are 82 times faster and 767 times smaller at the maximum than that of the REM.

DOI： 10.1080/10407790600878726

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

The effects of three-dimensional (3D) radiative heat transfer in cloud fields are investigated by using the radiation element method by ray emission model (REM2). We have performed a 3D radiative heat transfer simulation in two fair-weather cumuli that are subjected to solar and sky irradiation. One of the features in this simulation is that both shortwave radiation and longwave radiation are considered. As a result, the effect of shortwave radiation is not so substantial as compared with that of longwave radiation in terms of the heat generation rate within the cloud. Also, the radiative interaction does not strongly affect the relative differences of the average heat generation rate between the single cloud model and the double cloud model. However, the distributions of heat generation rate at the thin layer beneath the cloud surface are influenced by radiative interaction and shadowing effect. Hence, these effects caused by 3D radiative heat transfer are important for horizontal inhomogeneous cloud fields. (C) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jqsrt.2004.08.013

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper compares and scrutinizes the characteristics of radiation element method by ray emission model (REM2) and discrete ordinates interpolation method (DOIM). A three-dimensional radiative heat transfer problem is solved within a rectangular enclosure containing absorbing, emitting, nonscattering medium with temperatures given as a sine function. The calculation results are validated with the zonal results and the analytical solution. Generally, the calculation results agree well with the exact solution. However, when the optically thickness is much larger than unity, the zonal and REM2 results overestimate the heat source strength and wall heat flux, and when it is small, DOIM results underestimate them. The reasons and remedies are carefully discussed.

DOI： 10.1299/jsmeb.48.259

Scopus

researchmap

担当区分：筆頭著者  

researchmap

担当区分：筆頭著者  

researchmap

担当区分：筆頭著者  

researchmap

記述言語：英語  

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

記述言語：英語  

researchmap

researchmap

記述言語：日本語   出版者・発行元：公益社団法人 日本工学教育協会  

CiNii Article

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

開催年月日： 2019年7月

researchmap

開催年月日： 2019年4月

researchmap

開催年月日： 2019年1月

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

researchmap

受賞国：日本国

researchmap

受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

researchmap

researchmap

researchmap

researchmap

受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

researchmap

受賞国：日本国

researchmap

受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

researchmap