SEISAN KENKYU
Online ISSN : 1881-2058
Print ISSN : 0037-105X
ISSN-L : 0037-105X
Volume 65 , Issue 1
Showing 1-16 articles out of 16 articles from the selected issue
Preface
Introduction to Special Section
Research Flash
  • -Review on activities of support corps in Tokyo during the 2011 Great East Japan Earthquake-
    Xuan CHENG, Shinsuke KATO, Kyosuke HIYAMA, Sihwan LEE
    2013 Volume 65 Issue 1 Pages 5-8
    Published: January 01, 2013
    Released: June 05, 2013
    JOURNAL FREE ACCESS
    In recent years, with the developing of the energy-saving of residential house, the method of measuring accurately the thermal performance of the existing houses installed with the thermal insulating accurately is important. The purpose of this study is to develop a diagnostic method for this thermal insulation performance. This paper describes the method to measure the thermal insulation performance of the ceiling in residential house. The overall heat transfer coefficient of different ceiling locations were calculated by using CFD. The simulation results show that the convection heat transfer coefficient was increased by direct high-speed flow and the thermal current.[This abstract is not included in the PDF]
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  • Shi CHEN, Shinsuke KATO, Yoonkyung KANG, Keisuke NAKAO
    2013 Volume 65 Issue 1 Pages 9-12
    Published: January 01, 2013
    Released: June 05, 2013
    JOURNAL FREE ACCESS
    In this paper, we simulated person's motion by Computational Fluid Dynamic. We studied how the motion affect the indoor airflow and hope to supply basic data for further studies on dynamic influence to the indoor air. Four kinds of parameters are calculated and discussed, including the horizontal distribution of air velocity and differential air pressure, fluid resistance over person's surface and the power of the resistance generated during the motion. The result shows that, compare with the power generated by ventilation (30 m3/h), the power of the resistance is much more bigger according to our simulation.[This abstract is not included in the PDF]
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Research Review
  • Keisuke NAKAO, Shinsuke KATO
    2013 Volume 65 Issue 1 Pages 13-19
    Published: January 01, 2013
    Released: June 05, 2013
    JOURNAL FREE ACCESS
    Fluctuation of concentration under the condition of building shaped obstacles array were analyzed by means of Large Eddy Simulation(LES). Stochastic properties were compared to the experimental results. Test region is the space which were pinched by two blocks centrally-located on the obstacles alignment. Although mean concentration of LES overestimated the value, relative properties such as skewness showed an agreement. The terms included in the transport equation of scalar variance were calculated. Peak location of variance and production of it were corresponded. The time scale ratio of scalar variance and kinetic energy were plotted in the target domain. The properties shows variability, however, it showed an agreement with an empirical value in the region where mean concentration took large value.
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Research Flash
  • Hideki KIKUMOTO, Ryozo OOKA
    2013 Volume 65 Issue 1 Pages 21-24
    Published: January 01, 2013
    Released: June 05, 2013
    JOURNAL FREE ACCESS
    We examined the effects of the subgrid-scale (SGS) variance of concentrations on the binary reaction rate of chemically reactive air pollutants in large-eddy simulations (LESs). LES coupled with an SGS variance model was used to analyze the dispersion of pollutants in an urban street canyon. First, we conducted simulations of an inert pollutant at different grid resolutions, and found the validity of the model for the SGS variance. Second, we applied the model to the dispersion of reactive pollutants. The SGS covariance became relatively large at the canyon height. However, it was very small and gave a negligible impact on the mean concentrations of pollutants within the canyon.[This abstract is not included in the PDF]
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  • Jongyeon LIM, Ryozo OOKA
    2013 Volume 65 Issue 1 Pages 25-29
    Published: January 01, 2013
    Released: June 05, 2013
    JOURNAL FREE ACCESS
    This paper summarized calculations of urban morphological characteristics for about 11 km2 area of Chiyoda-ku. A three-dimensional building data and urban terrain data were integrated and analyzed using a geographic information system. Some parameters describing the urban morphology that were calculated include the frontal area index, building plan area fraction, building area density, mean building height, variance of building height, aerodynamic roughness length and zero-plane displacement height. The results were then compared to the value of another parameter by correlation analysis. From these results, possibility of application was considered as index for optimal design method for building arrangement considering wind environment.[This abstract is not included in the PDF]
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  • Olivier PACOT, François AVELLAN, Chisachi KATO
    2013 Volume 65 Issue 1 Pages 31-34
    Published: January 01, 2013
    Released: June 05, 2013
    JOURNAL FREE ACCESS
    The purpose of this paper is to show the feasibility of a large-scale unsteady flow computation. This computation consists in the simulation of the rotating stall appearing into a pump-turbine operating at part load condition (Q/QBEP=76%) in pumping mode. The computations are performed using an Overset Finite Element Large Eddy Simulation (LES) code with the dynamic Smagorinsky turbulence model (DSM). To understand the onset and the propagation of the stall patterns a fine mesh is required in order to compute the small turbulence scales present in the turbulent boundary layer (TBL). In the present study such fine mesh features 8 billion elements.[This abstract is not included in the PDF]
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  • Takayuki SUZUKI, Chisachi KATO
    2013 Volume 65 Issue 1 Pages 35-39
    Published: January 01, 2013
    Released: June 05, 2013
    JOURNAL FREE ACCESS
    The objective of this study is to clarify causes of inability of homogeneous models to predict breakdown characteristics of cavitating hydrofoil accurately. Theoretical analysis shows that the present cavitation models inevitably cause kinetic energy loss through expansion and contraction of the media. To illustrate this fact, we computed cavitating flows in a venturi and around a hydrofoil (NACA0015) with a homogeneous model and investigated the computed flow field in detail. It is shown that the expansion and contraction of the media based on the homogeneous model do in fact cause kinetic energy loss and as a result, a region of low velocity appears downstream of the cavity. This results in a decrease of lift force in a partial cavitation condition, which is not observed in the corresponding measurements.[This abstract is not included in the PDF]
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  • Naoki MASUDA, Chisachi KATO, Yasumasa SUZUKI
    2013 Volume 65 Issue 1 Pages 41-44
    Published: January 01, 2013
    Released: June 05, 2013
    JOURNAL FREE ACCESS
    Decoupled method using the flow field and the sound field is widely used in research on aerodynamic noise. It is important that in order to accurately predict the aerodynamic noise generated by the flow around the bluff body with the laminar separation, be captured accurately process leading to the transition from the leading edge of the bluff body and large eddy structure of the wake. Therefore, we investigated the influence of the accuracy of the fluid analysis around the square cylinder as sound sources.[This abstract is not included in the PDF]
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  • Fujihiro HAMBA
    2013 Volume 65 Issue 1 Pages 45-48
    Published: January 01, 2013
    Released: June 05, 2013
    JOURNAL FREE ACCESS
    Two-equation models including the k-ε model are widely used for Reynolds-averaged Navier-Stokes simulations. However, the second model equation such as the dissipation rate equation has not been fully validated. In this work, the transport equation for the eddy viscosity is investigated to better understand turbulence and improve turbulence models. The nonlocal eddy viscosity representation for the Reynolds stress is first considered. A new length scale is introduced to express the local eddy viscosity. The transport equation for the eddy viscosity is derived using the length-scale equation. The transport equation is evaluated using a direct numerical simulation of turbulent channel flow and their physical meaning is investigated.[This abstract is not included in the PDF]
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  • Nobumitsu YOKOI
    2013 Volume 65 Issue 1 Pages 49-55
    Published: January 01, 2013
    Released: June 05, 2013
    JOURNAL FREE ACCESS
    Effects of turbulence on the magnetic reconnection are investigated. Turbulence effects enter into the mean magnetic-field and momentum equations through the turbulent electromotive force and the Reynolds (and turbulent Maxwell) stresses. By considering the mean-field equations with these turbulent effects, it is analytically shown that the mean magnetic field and the mean flow are induced in the presence of turbulent cross helicity (correlation between the velocity and magnetic-field fluctuations). Such induced mean fields are expected to contribute for the fast reconnection. With the aid of the analytical expressions for the induced fields, it is shown how the reconnection rate depends on the turbulent cross helicity. It is also inferred that the dynamic balance between the transport enhancement due to the turbulent energy and the transport suppression due to the turbulent cross helcity plays an essential role in confining the reconnection region into a tiny one.[This abstract is not included in the PDF]
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  • Taketo ARIKI, Fujihiro HAMBA
    2013 Volume 65 Issue 1 Pages 57-60
    Published: January 01, 2013
    Released: June 05, 2013
    JOURNAL FREE ACCESS
    The turbulence electromotive force in the Hall-MHD turbulence has been investigated based on two-scale direct-interaction approximation (TSDIA) which is a series of analytical treatments of inhomogeneous turbulence. In the present work the treatment of the propagator of the nonlinear interaction between velocity and magnetic fields in the sense of renormalized perturbation method. As a result a new term has been derived in the electromotive force which suggests that the aliment between velocity and magnetic fluctuations in small scale can cause effective electromotive force parallel to the mean magnetic field.[This abstract is not included in the PDF]
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  • Md. Nazrul ISLAM, Daisuke KITAZAWA
    2013 Volume 65 Issue 1 Pages 61-64
    Published: January 01, 2013
    Released: June 05, 2013
    JOURNAL FREE ACCESS
    Harmful algae produce toxin in eutrophic lakes. The toxin production model is developed and applied to the ecosystem in Lake Kitaura. As a result, the toxin concentration is higher in the northern area since algal abundance is higher and algal growth is limited by the concentration of dissolved inorganic phosphorus. The horizontal distribution of toxin concentration cannot be reproduced unless the change in the toxin production rate is modeled based on whether phosphorus or nitrogen limits the algal growth. Higher toxin production in the phosphorus limited case should be assessed enough in the management of water quality in eutrophic lakes.[This abstract is not included in the PDF]
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Research Paper
Research Flash
  • Jie HE, Yutaka TOI
    2013 Volume 65 Issue 1 Pages 65-68
    Published: January 01, 2013
    Released: June 05, 2013
    JOURNAL FREE ACCESS
    In this paper, a new phase transformation mechanism in SMA computational model has been proposed and validated. The main purpose for developing this model is to reduce conventional models'systematic error due to their fixed shape transformation hardening functions. The new model adopted a modified version of logistic sigmoid function to obtain flexibility. Material level identification and structural level prediction have been conducted. Both validations show better results than the conventional models. Further applications of this model are expected in the future.[This abstract is not included in the PDF]
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  • Jie HE, Yutaka TOI
    2013 Volume 65 Issue 1 Pages 69-73
    Published: January 01, 2013
    Released: June 05, 2013
    JOURNAL FREE ACCESS
    Two improvements to conventional SMA computational models have been introduced in this paper. One is twinned martensite phase support for SMA simulation in low temperature. Another is special treatment in phase transformation condition for SMA simulation in hysteresis environment. Both improvements are essential for SMA actuator simulations. Two successful numerical examples including SMA honeycomb structure tensile behavior and SMA honeycomb core actuator proved the validity of those improvements with additional physical findings. Further implementations of the new model are expected.[This abstract is not included in the PDF]
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