Wind tunnel experiments about transfer coefficient in urban surfaces and modeling of city structure.

城市对流热通量的模拟是热岛研究的重要问题之一。本文采用自行设计的“水蒸发法”研究了城市峡谷内对流传递系数的分布。该技术的优点是可以精确地测量对流通量，与类似的热通量实验相比较。此外，我们可以很容易地限制在任意表面上的通量，甚至在表面内的部分。本文主要研究了峡谷几何形状对三维立方阵列的影响。测量了不同密度下对流传递系数的垂直分布，并考察了对流传递系数随风向的变化。在同一曲面内，系数的变化是不可忽略的，这意味着，如果假设所有位置都是恒定值，在某些情况下会导致相当大的误差。另一个课题是屋面形状对对流传递系数的影响。实验采用二维坡屋顶模型（倾角为平面至65.4度）。揭示了各种模型表面和模型间街道表面的系数分布。虽然这些关于循环规则排列的实验为城市结构的建模提供了基础信息，但我们必须检查这种简化的排列是否被认为是实际城市的代表。因此，我们也采用相同的水蒸发技术测量了真实存在的城市模型沿街道的分布。同一街道内各点之间差异显著，最大值超过最小值的2倍。由于对流传递系数与风速或扩散能力密切相关，因此可以认为这些结果也代表了各个位置的通风量。

The modeling of convective heat flux in urban area is one of the important problems in heat island study. In this paper, the distribution of convective transfer coefficient within urban canyon is investigated using our originally devised "water evaporation technique". The merit of this technique is to measure the convective flux precisely, in comparison with similar experiments about heat flux. Besides, we can easily restrict the flux in an arbitrary surface or even the portion within the surface.The main topic in this study is the effect of canyon geometry about three-dimensional cubic array. The vertical distributions of convective transfer coefficient were measured in various densities and its change due to wind direction was also examined. The variation of coefficient within same surface is not negligible, that means, if constant value assumed for all position it leads to considerable error in some case. Another topic is the effect of roof shape on convective transfer coefficient. The two-dimensional models with gable roof (inclination from flat to 65.4 degree) were used in experiments. The distributions of coefficient were revealed in all kind of model surface and street surface between models.Though these experiments about cyclic regular arrangement give fundamental information for modeling of urban structure, we have to check whether such a simplified arrangement is considered as a representative of actual city. Therefore, we also measure the distribution along a street of real existed city model using same water evaporation technique. The difference among points within the same street is remarkable, and maximum value exceed twice of minimum point. As convective transfer coefficient is closely related with wind speed or diffusion ability, it can be considered that these results are also representative of ventilation rate in each position.