規則的に配列されたブロック上空の低速ストリーク構造の特性

抄録

Low-speed streaks over the square arrayed cubes are investigated using large-eddy simulation. A simplified model city was created by arranging blocks in a cube of width H and at a distance of H. Previous studies conducted on simplified arrayed cubes have focused on fully developed turbulent flows. However, the generating mechanism of the low-speed streaks over the square arrayed cubes was unknown. In this study, large-eddy simulation was performed for the transition flow from uniform flow to turbulent flow over the square arrayed cubes to investigate the generating mechanism of the low-speed streaks. The source of the low-speed streaks observed above the cubes was near the ground surface at the second row. This is the position where the influence of the separation flow generated at the first cubes begins to decrease and the inner boundary layer begins to develope. The size of low-momentum fluid increases toward downwind, and is observed as a streak. The occurrence of the low-speed streaks above the cubes was caused by separation flow and ejection of the low-speed streak near the floor. The low-speed streaks fully develop after the 7th row, and the low-speed streak is generated with a certain period.