The effects of various velocity fluctuations of upper flow on turbulent structure of urban boundary layer were experimentally investigated. The urban boundary layer was reproduced in a wind tunnel. In order to produce various velocity fluctuations in the upper flow, three kinds of turbulence grids were set to the entrance of the test section. The streamwise and spanwise velocities were simultaneously measured by using hot-wires anemometer. Turbulence statistics were estimated. The vertical profiles of the integral time scale, , for M50 , M75 and the unequally spaced turbulence grid decrease as z/L increases. The vertical profile of Δ of the unequally spaced turbulence grid was larger than those for M50 and M75 at z/L > 0.167. It is suggested that the effects on the turbulent structure of the urban boundary layer depends on the scale of velocity fluctuations of the upper flow.
SAKUNO et al. (Wed,) studied this question.