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天空遮挡是指在地表任意处所见天空受周围建筑、树或其他构筑物形成的遮挡。本文提出一种城市天空遮挡的简化算法,算法采用反三角函数解析法计算遮挡高度角,进而得到天空角系数、阴影率和日照时数等参数。通过脚本语言编制Rhino&Grasshopper参数化平台插件实现算法的自动计算。通过理想算例、建筑群算例和实际城市住区算例的对比计算,证明简化算法具有较高计算精度和稳定性,可满足工程设计要求,其中,SVF计算值的根均方差≤0.04,一致性指数≥0.99,SAR计算值的根均方差≤0.101,一致性指数≥0.96。对比以往插件和软件,简化算法插件的计算耗时更短而整体运算效率更高。本文给出的算法及插件,可为城市设计初步方案在城市微气候、室外热舒适和建筑能耗等方面性能的评价与优化提供关键技术支持。
Sky blocking means that the sky seen anywhere on the surface is covered by surrounding buildings, trees or other structures. In this paper, we propose a simplified algorithm for urban sky occlusion. The algorithm uses the inverse trigonometric method to calculate the occlusion elevation angle, and then obtains the parameters of sky angle, shadow ratio and sunshine hours. Through the scripting language preparation Rhino & Grasshopper parameterization platform plug-in algorithm to automatically calculate. Comparing the ideal case study, the case study with the actual urban settlement case, the simplified algorithm is proved to have high accuracy and stability, which can meet the engineering design requirements. Among them, the root mean square error of the SVF calculation value is ≤0.04, The consistency index ≥0.99, the root mean square error of SAR calculation value ≤0.101, the consistency index ≥0.96. Compared with the past plug-ins and software, simplifying the algorithm plug-in calculation is shorter and the overall operation efficiency is higher. The algorithms and plug-ins given in this paper can provide key technical support for the evaluation and optimization of the initial urban design scheme in terms of urban microclimate, outdoor thermal comfort and building energy consumption.