Investigation of wind characteristics over an urban city by observation and wind tunnel experiment

The aim of this study is to investigate and clarify the wind characteristics over an urban city. Long-term field measurement of vertical distribution of wind speed and wind direction has been conducted using doppler scanning lidar in the central part of Tokyo. Meteorological phenomena, such as sea breezes in summer and strong winds due to typhoons, were observed. Wind conditions over an urban city are influenced not only by meteorological factors but also by surrounding high-rise buildings. The influence of buildings approximately 200m in height was observed even at heights of 300m or more above ground level, the vertical distribution of wind speed varied greatly due to the influence of the surrounding buildings under strong wind condition.

The wind tunnel experiments were conducted by using the architectural model of filed measurement region which scale 1/1000 to investigate the influence of high-rise building on wind conditions. Wind velocity was measured by hot-wire probe and Particle image velocimetry (PIV) measurement. In the measurement using hot-wire probe, a similar trend to the results of long-term field measurement was shown. PIV measurements were conducted with two inflow conditions of different turbulence intensity. It was confirmed that in the case of a low turbulence intensity, the low wind speed region behind a high-rise building was wider. This result shows that the condition of the urban area upwind of the high-rise buildings also affects wind conditions.