SEISAN KENKYU
Online ISSN : 1881-2058
Print ISSN : 0037-105X
ISSN-L : 0037-105X
Volume 64 , Issue 1
Showing 1-22 articles out of 22 articles from the selected issue
Preface
Introduction to Special Section
Research Flash
  • Fujihiro HAMBA
    2012 Volume 64 Issue 1 Pages 9-12
    Published: 2012
    Released: March 08, 2012
    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 diffusivity is investigated to better understand turbulence and improve turbulence models. The nonlocal eddy diffusivity representation for the turbulent scalar flux is first considered. A new length scale is introduced to express the local eddy diffusivity. The transport equation for the eddy diffusivity 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]
    Download PDF (2128K)
  • Nobumitsu YOKOI
    2012 Volume 64 Issue 1 Pages 13-19
    Published: 2012
    Released: March 08, 2012
    JOURNAL FREE ACCESS
            Coupled with the large-scale vortical motion, the cross-correlation between the velocity and magnetic-field fluctuations contributes to the turbulent electromotive force. The cross correlation is expected to play an important role in dynamo actions in particular in the cases with global rotational motions. In order to estimate how much the cross-correlation exists in turbulence, we need proper evaluation of the cross-correlation dissipation rate as well as its production rate. With the aid of analytical statistical theory of inhomogeneous magnetohydrodynamic (MHD) turbulence, we derived two types of model for the turbulent cross-correlation dissipation: (i) the algebraic model; and (ii) the transport equation of the turbulent cross-correlation dissipation. Relationship between these two models is discussed. [This abstract is not included in the PDF]
    Download PDF (3250K)
  • Shoji KOYAMA
    2012 Volume 64 Issue 1 Pages 21-25
    Published: 2012
    Released: March 08, 2012
    JOURNAL FREE ACCESS
            Natural convection between two differently heated vertical walls is investigated by large-eddy simulation. In this study, the scale similarity model by Bardina et al. is used to reproduce the subgrid-scale (SGS) heat-flux vector in place of the gradient diffusion model. As a result, the Bardina model can reproduce the SGS heat flux in streamwise direction as accurately as an existing model does. But even the Bardina model cannot reproduce mean velocity. It is therefore necessary that the SGS stress tensor model should be also modified. [This abstract is not included in the PDF]
    Download PDF (1380K)
  • Taketo ARIKI, Fujihiro HAMBA
    2012 Volume 64 Issue 1 Pages 27-30
    Published: 2012
    Released: March 08, 2012
    JOURNAL FREE ACCESS
            In this article, we have proposed a tentative method to analyze the inhomogeneity effect of the turbulent flow in theoretical way. The method is based on the Two-scale DIA (TSDIA) and Mean-Lagrangian Two-Scale Renormalization (MLTSR), which are those of few theoretical methods for inhomogeneous turbulent flow. With this new method we have calculated the Reynolds stress as a concrete example following the MLTSR and confirmed that it can successfully produces the inhomogeneity effects which are peculiar to the inhomogeneous turbulent flow.[This abstract is not included in the PDF]
    Download PDF (1782K)
  • Koichiro NEMOTO, Fujihiro HAMBA
    2012 Volume 64 Issue 1 Pages 31-34
    Published: 2012
    Released: March 08, 2012
    JOURNAL FREE ACCESS
            When we think the influence of MHD turbulence on the dynamo mechanisms, turbulent electromotive force is important. Until now α and β term had been considered as RANS model of turbulent electromotive force. Recently the new term proportional to the mean vorticity was suggested by analysis of statistical theory of the turbulence (TSDIA). In this study, I carried out the direct numerical simulation of the MHD thermal convection with homogeneous magnetic field and system rotation, and I examined turbulent statistics related to the transport coefficient of the RANS model. Furthermore, I considered physical picture of the generation term of turbulent electromotive force. [This abstract is not included in the PDF]
    Download PDF (2086K)
  • Md. NAZRUL Islam, Daisuke KITAZAWA, Ho-Dong PARK
    2012 Volume 64 Issue 1 Pages 35-40
    Published: 2012
    Released: March 08, 2012
    JOURNAL FREE ACCESS
            Dominant species of cyanobacteria produce highly potent toxins Microcystin in a shallow and eutrophic Lake. Toxin production is generally the result of two major factors-natural processes and human interferences. Most of the existing studies are related to experiment about cyanobacteria spur blooms. Thus the purposes of this study, a three dimensional hydrodynamic ecosystem coupled model were employed and used to create a toxin production model. The numerical model was calibrated by tuning a toxin decay coefficient, half saturation constant of phosphorus and nitrogen and other input parameters for achieving a good agreement between the observations and the predictions. [This abstract is not included in the PDF]
    Download PDF (1287K)
  • Toru YAGI, Daisuke KITAZAWA, Satoshi ABE, Fujihiro HAMBA, Shinsuke KAT ...
    2012 Volume 64 Issue 1 Pages 41-45
    Published: 2012
    Released: March 08, 2012
    JOURNAL FREE ACCESS
            In this paper, reverse simulation for ocean problem is investigated, which is a method to specify pollutant source that causes pollution problems. Reverse simulation is the solution of a transport equation in negative time advancing and there is a problem of a numerical instability with solving the negative diffusion term. In reverse simulation with the filter applied to keep numerical stability, the relationship between the effect of the filter and the boundary condition, which is one of the causes of the numerical instability, is examined by the changes in the distribution of pollutant. [This abstract is not included in the PDF]
    Download PDF (1706K)
  • Jia HE, Sihwan LEE, Shinsuke KATO, Kouichi TATSU
    2012 Volume 64 Issue 1 Pages 47-50
    Published: 2012
    Released: March 08, 2012
    JOURNAL FREE ACCESS
            In summer the hot outside environment often increases the air temperature in a truck cabin to a high level, which makes drivers very uncomfortable. It is often reported that the concentration of VOCs which is unhealthy for drivers in truck cabins will tend upward caused by high-temperature environment. At the same time, the air-conditioning load for cooling truck cabins is large. In this study, a double-ceiling ventilation system for trucks is presented and the effects on thermal environment improvement for truck cabins are discussed by CFD analysis. [This abstract is not included in the PDF]
    Download PDF (1361K)
Research Review
Introduction to Special Section
Research Review
  • Katsuyoshi IKEUCHI, Jun YANAGIMOTO
    2012 Volume 64 Issue 1 Pages 75-82
    Published: 2012
    Released: March 08, 2012
    JOURNAL FREE ACCESS
        Hot stamping is one of the hot forming processes for manufacturing products of lightweight vehicles. Knowledge on the characteristics of the hot stamping process is significant in designing and optimizing the process conditions, dies and tools; however, until now, the characteristics of this process have not been clarified consistently or precisely. A new valuation method used to measure the effects of hot stamping conditions on product properties as a function of process parameters is proposed in this paper. This method utilizes a hot forming simulator and permits to know the various characteristics of the hot stamping process. Here, the basic construction of the proposed method is presented, and its application to the characterization of the hot stamping process of high-strength steel sheets is shown and discussed.
    Download PDF (5812K)
Research Flash
  • Kensuke TSUCHIYA, Toru NUNOKAWA, Atsunori KIKUCHI, Masayuki NAKAO
    2012 Volume 64 Issue 1 Pages 83-86
    Published: 2012
    Released: March 08, 2012
    JOURNAL FREE ACCESS
            This paper reports a multilayered micro-reactor of thin metal plates for a higher heat transfer efficiency compared with glass or silicon plates. In addition, diffusion bonding is used to bond the plates, because it is possible to bond a lot of plates in one process. We chose stainless steal SUS316 as a material of the micro-reactor. It is suitable for micro-reactors for its high corrosion resistance. We investigated bonding strength of the test pieces and optimize the parameters of bonding condition. We measured tensile strength and the Charpy value. The result indicates that the higher bonding temperature provides higher bonding strength and less voids. On the other hand, the deformation of the micro-channels should be small. We prototyped a multilayered micro-reactor at 10MPa, 1100 degree Celsius. It has totally 20 layers for reaction and coolant. We demonstrated a exothermic reaction with acid, which is nitration of benzene, using the prototype. From the experiment, it is proved that the diffusion bonding improved the heat transfer efficiency of the micro-reactor. [This abstract is not included in the PDF]
    Download PDF (997K)
  • Toshiyuki OBIKAWA, Kazuhiro FUNAI
    2012 Volume 64 Issue 1 Pages 87-90
    Published: 2012
    Released: March 08, 2012
    JOURNAL FREE ACCESS
            Air jet assisted (AJA) machining was applied to high speed machining of nickel-base superalloy Inconel 718 with a SiC whisker reinforced ceramic tool. As a result, the air jet applied to the tool tip reduced the notch wear of a ceramic tool at the depth of cut line to extend the tool life cutting length. It was found that the tool life can be extended further by optimizing the pressure of the air jet in AJA machining. [This abstract is not included in the PDF]
    Download PDF (1049K)
  • Yoji OKABE, Naoko WATANABE, Mamoru SHIMAZAKI
    2012 Volume 64 Issue 1 Pages 91-94
    Published: 2012
    Released: March 08, 2012
    JOURNAL FREE ACCESS
            The authors attempted to extend the function of our ultrasonic health monitoring system with FBG sensors to detect large strain waves caused by impact loads. First, tensile tests were conducted to obtain the relational equations between the Bragg wavelength of FBG and the normalized outputs of this system for compensation of nonlinear relations. Then, an impact test was conducted to a CFRP laminate on which an FBG was bonded. After that, through inverse calculation to the measured output using the relational equations, the impact strain wave could be reconstructed precisely. Furthermore, we succeeded in detection of larger strain waves by three multiplexed FBGs simultaneously. [This abstract is not included in the PDF]
    Download PDF (1927K)
Research Review
Research Flash
  • Yasuyuki KAMIMURA, Yasuhiro TANI, Kensuke TSUCHIYA, Mitsuru NUKUI
    2012 Volume 64 Issue 1 Pages 103-108
    Published: 2012
    Released: March 08, 2012
    JOURNAL FREE ACCESS
            A zirconia capillary is a key component of an optical fiber connector. Center holes of zirconia capillaries have been conventionally finished in loose abrasive process using a long taper wire. In this process both the productivity and the defect rate were very low. In order to overcome the problems, internal grinding utilizing an electroplated diamond taper wire was attempted. In the condition that the grain depth of cut was large, the diamond grains were stuck to the workpiece and the diamond wire was easily twisted off. Then low-frequency vibration was added to the workpiece and continuous grinding was stably enabled when the amplitude of the vibration exceeded 3 mm. At the same time the length of a taper section was clarified to be important and a taper section longer than 60 mm was desirable. Continuous grinding over 60 pieces was accomplished with high throughput within 30 seconds. [This abstract is not included in the PDF]
    Download PDF (1833K)
  • Shuhei NISHIDA, Dai KOBAYASHI, Takeo SAKURADA, Hideki KAWAKATSU
    2012 Volume 64 Issue 1 Pages 109-111
    Published: 2012
    Released: March 08, 2012
    JOURNAL FREE ACCESS
    Download PDF (874K)
  • Hitoshi HARAGUCHI, Toshiki NIINO
    2012 Volume 64 Issue 1 Pages 113-119
    Published: 2012
    Released: March 08, 2012
    JOURNAL FREE ACCESS
            In plastic laser sintering, continuous preheating is essential from warming up stage through the whole laser sintering process to prevent undergoing parts from warping. The authors are proposing plastic laser sintering without powder bed preheating by fixing in-process parts to the base plate. In this paper, feasibility of the process is investigated. Stress relieve annealing successfully reduced the residual stress and warpage. A high relative density of 92% was obtained after experimental-based parameter optimization. Although tensile and impact strength decreased to 40~60% of heating process, elongation at break increased to 135%. Electricity consumption was drastically reduced since powder bed preheating was omitted. Capability of process resumption after 30 minutes interruption was confirmed improving robustness against blackout. [This abstract is not included in the PDF]
    Download PDF (2465K)
feedback
Top