Choosing appropriate sites for wind turbines is extremely important in Japan because the spatial distribution of wind speed is highly complex over steep complex terrain, which is abundant in Japan. The author's research group has been developing an unsteady CFD software package called RIAM-COMPACT®. This package is based on an LES turbulence model. In this paper, to examine the accuracy of RIAM-COMPACT®, numerical simulations of uniform, non-stratified airflow past a three-dimensional cube were performed. The analysis primarily focused on airflow characteristics in the wake region. The results from the simulation with RIAM-COMPACT® were compared to those from a commercially-available CFD software package (STAR-CCM+) and were found to be in good agreement.
A three-dimensional (3D) Haasen-Alexander-Sumino model (HAS model) has been developed to study the dislocation density and residual strain in the crystal. We compared the difference between calculation results and experimental results. The results show that the HAS model can evaluate the dislocation density and residual strain in the crystal semiquantitatively. And the residual strain for a multicrystal is lower than that for a mono-like crystal. In the case of mono-like crystal, the dislocation generation is small and the thermal stress cannot relax easily, then residual strain is high. In the case of the multicrystal, the dislocation generation is large and there are so many grains, then the thermal stress can relax easily and residual strain is low.
Heterogeneous processes play an important role in changing the chemical, physical, optical, and radiative characters of dust particles at regional and global scales, especially in East Asia, where both the emissions of mineral dust and anthropogenic pollutants are huge. To investigate the chemical and physical impacts of heterogeneous reactions on dust particles, three dust and/or air pollution episodes were observed and simulated in Beijing, China and Fukuoka, Japan during 27 March and 2 April, 2015. The results confirmed that heterogeneous reactions were the major mechanisms producing coarse mode nitrate and sulfate in the presence of dust particles, with the concentrations of coarse mode nitrate reaching 19 μg/m in Beijing and 4 μg/m in Fukuoka. We also found that heterogeneous processes and subsequent hygroscopic growth significantly changed the mixing state and size of dust particles. As a result of the internal mixing of nitrate, sulfate, and aerosol liquid water, the volume concentration of dust doubled when the relative humidity (RH) was relatively high (> 80%), and the dust particles tended to be spherical when the volume fraction of dust coatings reached 20%.
Selecting a high-quality site for wind turbine installation is frequently challenging in Japan because the majority of the topography of Japan is steep complex terrain and the spatial distribution of the wind speed is quite complex over such terrain. To address this issue, an unsteady CFD model called RIAM-COMPACT® has been developed. RIAM-COMPACT® is based on an LES turbulence model. In the present paper, to assess the accuracy of RIAM-COMPACT®, we performed a numerical simulation of uniform, non-stratified airflow past a three-dimensional isolated-hill. Attention is focused on airflow characteristics in the wake region. The results of RIAM-COMPACT® using the LES model were in good agreement with those of another commercially-available CFD software (STAR-CCM+) using LES models.
One arc-minute resolution grid bathymetry of the East China Sea has been developed by compiling a large number of sounding data derived from various sources. The dataset was found to retain advantages of two existing grid bathymetries: representing basic bottom features found in navigational charts as in skkutopo1m dataset, while it resolves detailed bottom features observed in gebco2014 gridded bathymetry. Through comparisons between new and nine existing datasets, spurious bottom features in previous datasets were identified in near-coast regions and in areas where the source data were sparsely distributed. The verification also has clarified the regions where additional sounding records are required to improve the data quality.
The present study compared the prediction accuracy of two CFD software packages for simulating a flow around a three-dimensional, isolated hill with a steep slope: 1) Meteodyn WT (turbulence model: k-L RANS), which is one of the leading commercially available CFD software packages in the wind power industry and 2) RIAM-COMPACT® (turbulence model: the standard Smagorinsky LES), which has been developed by the lead author of the present paper. Although the Reynolds number settings differed between the simulation with Meteodyn WT and that with RIAM-COMPACT®, distinct differences in the flow patterns were identified in the vicinity of the isolated hill (especially downstream of the isolated hill) between the flows simulated by the two CFD software packages.
Because a significant portion of the topography of Japan is characterized by steep, complex terrain, which results in a complex spatial distribution of wind speed, great care is necessary for selecting a site for the construction of wind turbines. We have developed a computational fluid dynamics (CFD) model for unsteady flow called Research Institute for Applied Mechanics, Kyushu University, COMputational Prediction of Airflow over Complex Terrain (RIAM-COMPACT®). The RIAM-COMPACT® CFD model is based on the large-eddy simulation (LES) technique. In this paper, a numerical wind simulation for the Taikoyama Wind Farm is performed using high-resolution terrain elevation data. The results suggest that all six wind turbines at the Taikoyama Wind Farm are subject to significant influence from separated flow (terrain-induced turbulence) which is generated due to the topographical irregularities in the vicinity of the wind turbines. A proposal has been also made on reconstruction of the wind farm.
The Alexander-Haasen model was originally used to model the multiplication of the mobile dislocations in crystalline silicon. Here, we extend this model for studying multiplication of basal plane dislocations (BPDs) in single-crystal sapphire. By fitting the Alexander-Haasen model to experimental data, we find that the model accurately describes the plastic deformation of sapphire caused by BPDs. The application of the Alexander-Haasen model to sapphire growth made it possible to minimize the dislocation density and residual stress in growing crystals by optimizing the furnace structure and operation conditions. We apply the Alexander-Haasen model to investigate the dynamical deformation of single-crystal sapphire during the cooling process and examine the effect of the cooling rate on the generation of BPDs and residual stress. Finally, we present the BPD distribution and discuss the main factor that influences the generation of BPDs.
In the present study, wind conditions were numerica lly predicted for the site of the Bolund Experiment using the RIAM-COMPACT ® natural terrain version software, which is based o n an LES turbulence model (CFD). In addition, airflow measurements were made using a split-fiber probe in the boundary layer wind tunnel of the Inst itute of Industrial Science, University of Tokyo (a facility of the research group of Prof. Chisachi Kato). The characteristics of the airflow at and in the vicinity of the site o f the Bolund Experiment were clarified. The study a lso examined the prediction accuracy of the LES turbulence simulatio ns (CFD). The values of the streamwise (x) wind vel ocity predicted by the CFD model were generally in good agreement with those from the wind tunnel experiment at all points and heights examined, demonstrating the vali dity of CFD based on LES turbulence modeling.
