Abstract
In this research, the computational fluid dynamic (CFD) approach was applied for the solution of the problems of local strong wind areas in railway fields, and the mechanism of wind generation was discussed. The problem of local wind occurring on a railway line in winter was taken up in this research. A computational simulation for the prediction of wind conditions by large-eddy simulation (LES) was implemented, and it was clarified that local strong wind areas are mainly caused by separated flows originating from small-scale terrain positioned at its upstream (at approximately 180 m above sea level). Meanwhile, the effects of the size of the calculation area and spatial grid resolution on the result of calculation and the effect of atmospheric stability were also discussed. It was clarified that in order to simulate the air flow characteristic of the separated flow originating from the small-scale terrain (at an altitude of approximately 180 m) targeted in the present research, approximately 10 m of spatial resolution of computational cell in the horizontal direction is required. In addition, the effect of stable stratification on the flow was also examined. As a result, lee waves were excited at the downstream of the terrain over time in the case of stably stratified flow (Fr = 1.0). The reverse-flow region lying behind the terrain, which had been observed at a neutral time, was strongly inhibited. Consequently, a local strong wind area was generated at the downstream of the terrain, and a strong wind area passing through the observation mast was observed. By investigating the increasing rate of speed of the local strong wind area induced at the time of stable stratification, it was found that the wind was approximately 1.2 times stronger than what was generated at a neutral time.
Highlights
At present, the wind power generation business is rapidly growing at an unprecedented rate around the world. is is due to it having the best cost performance in attaining the avoidance of fossil fuels and the reduction of CO2 generation among all renewable energies
A separated flow originating from the small-scale terrain adheres to the ground; along with that, a very strong wind area is formed locally, and it can be observed that it passes through the observation mast
A computational fluid dynamics (CFD) approach, which has been used in wind power generation fields, was applied as a solution for the problems of local strong wind areas in railway fields. e mechanism of wind generation was discussed, and at the same time, the effectiveness of its application to railway fields was discussed. e problem of the strong local wind that occurs on the railway line in winter was taken up in this research
Summary
The wind power generation business is rapidly growing at an unprecedented rate around the world. is is due to it having the best cost performance in attaining the avoidance of fossil fuels and the reduction of CO2 generation among all renewable energies. The problems of the delays of trains at times of strong wind in winter are often discussed Against these problems, the characteristics of the wind conditions of local strong wind areas generated around railway lines were discussed based on the measured data and the weather grid point value (GPV) data. A wind rose (nine months for whole period for data collected from July 2014 to March 2015) is shown, in which the time-series data set consisting of the measured data (5 m above ground) and corresponding wind direction of weather GPV data (10 m above ground) was evaluated. A computational simulation of wind conditions targeting the wind from west-northwest by LES will be conducted, and the generation mechanism of the local strong wind area will be discussed in detail. Average wind speeds by wind direction (solid line) from measured data and wind direction appearance frequency (dotted line) from weather GPV data
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