SEISAN KENKYU
Online ISSN : 1881-2058
Print ISSN : 0037-105X
ISSN-L : 0037-105X
Volume 66 , Issue 1
Showing 1-16 articles out of 16 articles from the selected issue
Preface
Introduction to Special Section
Research Flash
  • Fujihiro HAMBA
    2014 Volume 66 Issue 1 Pages 5-8
    Published: January 01, 2014
    Released: March 18, 2014
    JOURNAL FREE ACCESS
    In the theory of isotropic homogeneous turbulence, two-point velocity correlation is formulated in wavenumber space. For the modeling of inhomogeneous turbulence, one-point velocity correlation is often treated instead of two-point correlation because of its complex properties. In this work, the transport equation for the energy based on the two-point velocity correlation is formulated to better understand the energy transfer in inhomogeneous turbulence. The term of energy flow in the space of vector that represents the difference of location between the two points is investigated.
    Download PDF (666K)
  • Nobumitsu YOKOI
    2014 Volume 66 Issue 1 Pages 9-14
    Published: January 01, 2014
    Released: March 18, 2014
    JOURNAL FREE ACCESS
    The notion of dynamic balance between the transport enhancement and suppression due to turbulence is investigated in the context of magnetic reconnection. In order to examine this idea, a self-consistent turbulence model, constituted of a closed system of equations for the mean fields (density, momentum, energy, etc.) and for the turbulence statistical quantities [turbulent magnetohydrodynamic (MHD) energy, its dissipation rate, cross helicity, etc.], is proposed. In this framework, the turbulent energy as well as the turbulent cross helicity is generated and sustained by the inhomogeneities of mean fields without resorting to any external forcing. Our numerical results show that the reconnection rate depends on the level of turbulence, and that the turbulent cross helicity contributes to the fast reconnection through confining the enhanced transport region to a small region in the vicinity of the symmetry point. The results confirm that the dynamic balance between the transport enhancement and suppressionin turbulence plays some role in achieving a fast magnetic reconnection.
    Download PDF (4846K)
  • Taketo ARIKI, Fujihiro HAMBA
    2014 Volume 66 Issue 1 Pages 15-17
    Published: January 01, 2014
    Released: March 18, 2014
    JOURNAL FREE ACCESS
    The history effect on an algebraic-Reynolds-stress model, which had been theoretically derived by the author, was investigated in some canonical simple flows (2-D elongational flow, simple shear flow and axisymmetric flow). As a consequence, the authors found that both turbulence viscosity and turbulence-energy production shows delay responses against the mean strain rate.
    Download PDF (749K)
  • Yusuke NAKAMURA, Fujihiro HAMBA
    2014 Volume 66 Issue 1 Pages 19-22
    Published: January 01, 2014
    Released: March 18, 2014
    JOURNAL FREE ACCESS
    In k-ε model, the transport equation for turbulent energy k can be verified by DNS. However, the transport equation for dissipation rate ε does not necessarily correspond to the exact transport equation.
    In this work, the energy transfer from low wavenumber part to high wavenumber part is considered as dissipation rate. Its transport equation is derived and the energy flow is examined using result of DNS in turbulent channel flow.
    It is expected that the transport equation for dissipation rate ε can be verified and improved by this analysis.
    Download PDF (1060K)
  • Takayuki SUZUKI, Chisachi KATO
    2014 Volume 66 Issue 1 Pages 23-26
    Published: January 01, 2014
    Released: March 18, 2014
    JOURNAL FREE ACCESS
    Recent studies have revealed that homogeneous models which represent cavitation by the media whose density varies are unable to predict lift force acting on cavitating hydrofoils. On this subject, our past study has revealed the present homogeneous models inevitably cause kinetic energy loss through expansion and contraction of the media and result in underestimation of lift force. In this study, we proposed a new cavitation model which makes up for the energy loss with added volume force and computed cavitating flows around NACA0015. The result shows that the new model solves the problem of present homogeneous models.
    Download PDF (706K)
  • Yang GUO, Chisachi KATO, Yoshinobu YAMADE, Yutaka OHTA, Taku IWASE, R ...
    2014 Volume 66 Issue 1 Pages 27-31
    Published: January 01, 2014
    Released: March 18, 2014
    JOURNAL FREE ACCESS
    The noise generated from the internal flow in a centrifugal fan was computed by computational aero-acoustics (CAA). The sound sources were obtained by large-eddy simulation (LES) of turbulent flow in the centrifugal fan. The computed sound pressure level (SPL) is better than the result by Curle’s equation below 300 Hz and agrees fairly well with the experimental data in this frequency range. Sound pressure level (SPL) is overpredicted at high frequency region. Fluid forces at the plane perpendicular to the axial direction play important roles on the peak of SPL at blade passing frequency (BPF) 600 Hz.
    Download PDF (3080K)
  • Nazrul ISLAM Md., Daisuke KITAZAWA
    2014 Volume 66 Issue 1 Pages 33-37
    Published: January 01, 2014
    Released: March 18, 2014
    JOURNAL FREE ACCESS
    A three dimensional Marine Environmental Committee (MEC) model was run to describe the patterns of currents, water temperature, and salinity in Kamaishi Bay at Iwate Prefecture. The tidal elevation, water temperature, and salinity were reproduced well during January 2009. Then the effects of breaking waters were discussed by numerical simulation. Some changes could be found around the breakwater, while the change in circulation pattern was a little detected on the whole. As future studies, the resolution of grids will be improved and the effects of the breaking waters will be discussed in the context of the impacts on ecosystem.
    Download PDF (1434K)
  • Evaluation of Control Performance based on Convenience and Energy Consumption
    Yosuke HASEGAWA, Bettina FROHNAPFEL, Maurizio QUADRIO
    2014 Volume 66 Issue 1 Pages 39-42
    Published: January 01, 2014
    Released: March 18, 2014
    JOURNAL FREE ACCESS
    Flow control techniques for turbulent drag reduction in internal flows are typically evaluated under two alternative flow conditions, i.e. at constant mass flow rate or constant pressure gradient. Successful control leads to reduction of drag and pumping power at constant mass flow rate, whereas constant pressure gradient leads to an increase of the mass flow rate and pumping power. In practical applications, however, a compromise between the energy consumption and the corresponding convenience (flow rate) achieved with that amount of energy has to be reached so as to accomplish a goal which in general depends on the specific application.
    Based on this idea, we describe the derivation of two dimensionless parameters which quantify the total energy consumption and the required time (convenience) for transporting a given volume of fluid through a given duct. Performances of existing drag reduction strategies are re-evaluated within the present framework.
    Download PDF (1024K)
  • Minsik KIM, Shinsuke KATO, Ryohji OHBA, Masamichi OURA
    2014 Volume 66 Issue 1 Pages 43-45
    Published: January 01, 2014
    Released: March 18, 2014
    JOURNAL FREE ACCESS
    Download PDF (2580K)
Research Review
  • Hyokeun HWANG, Togo YOSHIDOMI, Shinsuke KATO
    2014 Volume 66 Issue 1 Pages 47-51
    Published: January 01, 2014
    Released: March 18, 2014
    JOURNAL FREE ACCESS
    The purpose of this study is to develop and evaluate an effective the indoor load handling system for energy saving in commercial building. A coupled simulation of convection and radiation is applied to examine the thermal characteristics on a surface of office equipment. The simulation boundary conditions is given by the result of a measurement performed under similar conditions. Using the simulation results, it is confirmed that the change of heat transfer occurs by convection and radiation in each surface. Also, to estimate the valid heating value for equipment and to improve the accuracy of the analytical model.
    Download PDF (1154K)
  • Keigo NAKAJIMA, Ryozo OOKA, Hideki KIKUMOTO
    2014 Volume 66 Issue 1 Pages 53-59
    Published: January 01, 2014
    Released: March 18, 2014
    JOURNAL FREE ACCESS
    Large-eddy simulation( LES) is performed to investigate the mechanism of the momentum and heat transport in an urban boundary layer with thermal stratification. From the results of LES, strong ejections which are generated at the top of the urban canopy (z/H=1.0) and are transported upward greatly contribute to Reynolds stress and turbulent heat flux. Model coefficient of eddy diffusivity for momentum Cμ and turbulent Prandtl number Prt which are estimated from the results of LES are smaller than the values which are used in standard k-ε model at some height. It is thought that the prediction accuracy of standard k-ε model decreases in the urban boundary layer.
    Download PDF (509K)
  • Yusuke ARIMA, Ryozo OOKA, Hideki KIKUMOTO, Toru YAMANAKA
    2014 Volume 66 Issue 1 Pages 61-68
    Published: January 01, 2014
    Released: March 18, 2014
    JOURNAL FREE ACCESS
    Climate change such as global warming is proceeding and climate conditions have huge impact on building performance. Thermal calculation is conducted to adapt a building to climate conditions using standard weather data which consists of weather components such as temperature and solar radiation. At present, it is common to use standard weather data that are based on current or past weather conditions. However, most buildings have a lifespan of several decades, during which climate can gradually change. Therefore, energy simulations should incorporate climate change predictions in order to ensure that buildings are adaptable to future climatic conditions and have long-term building performance. The purpose of this study is to construct future standard weather data which based on the future climate conditions using dynamical downscaling method with GCM.
    Download PDF (1004K)
Research Paper
Research Review
  • Shintaro IKEDA, Ryozo OOKA
    2014 Volume 66 Issue 1 Pages 69-77
    Published: January 01, 2014
    Released: March 18, 2014
    JOURNAL FREE ACCESS
    Although the smart grid aiming at the efficient utilization of energy and realization of a stable supply attracted attention in recent years, an innovation of the smart grid lagged behind the foreign country from the reasons of that the stability of an electric power system is very high in Japan, a regional monopoly type electric-power-industry structure, etc. However, some demonstration experiments are undertaken in Japan now, and the view of a future electric power system can be known through a research study about it. This study describes the leading-edge trend of four demonstration experiments of "the Demonstration of Next-Generation Energy and Social Systems".
    Download PDF (1939K)
Research Flash
feedback
Top