도시 협곡에서 수목이 흐름과 스칼라 물질 확산에 미치는 영향

Abstract

Abstract In this study, the effects of trees on flow and scalar dispersion in an urban streetcanyon were investigated using a computational fluid dynamics (CFD) model. For this, weimplemented the drag terms of trees to the CFD model, and compared the CFD-simulatedresults to the wind-tunnel results. For comparison, we considered the same building configura-tion as the wind-tunnel experiment. The trees were located at the center of street canyon withthe aspect ratio (defined as the ratio of the street width to the building height) of 1. First, theflow characteristics were analyzed in the tree-free and high-density tree cases and the resultsshowed that the CFD model reproduced well the flow pattern of the wind-tunnel experimentand reflected the drag effect of trees in the street canyon. Then, the dispersion characteristics ofscalar pollutants were investigated for the tree-free, low-density tree and medium-density treecases. In the tree-free case, the nondimensionalized concentration distribution simulated by theCFD model was quite similar to that in the wind-tunnel experiment in magnitude and pattern.The correlation coefficients between the measured and simulated concentrations are more than0.9 in all the cases. As the tree density increased, nondimensionalized concentration increased(decreased) near the wall of the upwind (downwind) building, which resulted from thedecrease in wind speed case by the drag effect of trees. However, the CFD model underesti-mated (overestimated) the concentration near the wall of upwind (downwind) building.Key words: CFD model, wind-tunnel experiment, tree-drag effects, flow and dispersion char-acteristics, street canyon