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]

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        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]

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        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]

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        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]

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        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]

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        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]

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        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]

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        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]

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    Great attention has been shown to the question about the building design and arrangement considering urban-ventilation. Recent years have witnessed the appearance of several studies and rating systems from this perspective. It might be included a wind environment rating system of CASBEE-HI (WERSC from here on) as a representative example. Curiously, despite the rise of studies about this rating system as an academic discipline, few have attempted to address its effectiveness. We will see in this paper how a wind environment of built area is being described by WERSC. Proceeding from what has been said in this paper, it should be concluded that WERSC is a debatable issue.

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    Network model is widely used in building energy simulation, which assumes perfect mixing and does not consider the temperature distribution. However it is considered to be improper for non-uniform indoor environment, and may lead to a large influence to the energy simulation result. In this study, energy simulation considering temperature distribution for a periodic air-conditioning system is achieved. A method coupling the contribution ratio of indoor climate (CRI) into network model is proposed in this paper, and the thermal load of a single office room is discussed. The effectiveness and predominance of this proposed method has been proved.

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The problem of the urban heat island effect in China is becoming serious, especially in inland cities. The target area of this research is Wuhan city, which is in the geographical centre of China, with vast areas of inland water bodies. With urbanization, the water area decreased to one third of the original area from 1965 to 2008. The purpose of this research is to quantitatively assess the impact of this huge amount of inland water body reduction on the local climate and environment. In order to achieve this, three cases of 1965, 2008, and an ideal case without water area inside the built-up zone are studied, and the Weather Research and Forecasting model (WRF) is introduced as a simulation tool.

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    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.

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        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]

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        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]

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        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]

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    The analysis of resin flow behavior in plastic injection molding process is an important theme which clarifies the causes of various molding defects. This paper aims to clarify three-dimensional resin flow behavior inside mold by discussing the principles and applications of visualization techniques. In particular, the colored-marking method using the rotary runner exchange system is a new method of visualizing three-dimensional flow behavior developed by the authors. Its potentials are also specifically discussed based on applications of the method.

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        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]

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        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]

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