Abstract
Solar radiation heats the wall and surface of canopy, generates a strong buoyancy flow, and by the long-wave radiation emitted from urban surface, air can be heated and also generate buoyancy. The impact of this buoyancy is more obvious at the condition of lower wind velocity. Since the flow pattern mainly depends on the wind velocity at the roof-top level, the exposure of the heating wall, and the canyon aspect ratio H/W, we conducted experiments on the mutual influence between wind velocity and surface temperature of asphalt heated by four halogen lamps which were used to present as solar radiation in wind tunnel (MRI, Tsukuba), and simulated the same condition to see the flow field distribution. Wind velocity above rooftop and surface temperature of the roof was measured. When wind is 1 m/s, the difference of velocity between heating and no heating condition can hardly be observed. The wind flows through the roof before getting influenced by the buoyancy flow generated by the heating roof. When wind is 0.5 m/s, velocity at heating condition is generally higher than that of no heating. A vortex was formed near the windward edge. From the results of calculation (CFD), we can see that the energy maintaining the vortex is from turbulent effect at the windward edge and momentum transport. This experiment is the first challenge to use artificial light (adjusted as same level of short wave radiation at the roof top) as radiation and real building materials in wind tunnel.
