拱坝坝面太阳辐射强度计算

Ray-tracing algorithm for solar radiation intensity computation of arch dam surface

本文基于三维拱坝有限元模型,建立了采用ASHRAE晴空模型,利用光线追踪算法准确计算周围地形和自身遮蔽的坝面太阳辐射计算框架。该方法能够准确计算拱坝坝面太阳辐射的不均匀分布,为温度场计算提供准确的边界条件。现场实拍照片与计算瞬时坝面辐射的比较,验证了光线追踪算法的准确性。冬季和夏季日平均太阳辐射计算结果表明,坝面太阳辐射分布随季节变化明显,以某工程为例,冬季左右岸差值可达100W/m2。考虑太阳辐射以后的计算温度场与实测值符合良好,证明该方法可用于工程实际。对计算结果的分析表明,拱坝的日平均太阳辐射主要是太阳直射辐射。坝面辐射分布主要由拱坝朝向决定,辐射强度由坝址纬度和朝向共同作用。

Based on the 3-D FEM a computation procedure of arch dam surface solar radiation is established. The ASHRAE clear sky model and the ray-tracing algorithm were introduced. By using this method the shade of surrounding terrain and structure can be carefully considered. The distribution of solar radiation on dam surface can be computed by the method and accurate thermal boundary conditions of the dam temperature field are obtained. The accuracy of the ray-tracing algorithm is verified by the comparison between real scene photo and the distribution of instant dam surface radiation calculated by the proposed procedure. The computation results of daily average solar radiation intensity on the typical day in summer and winter in a typical dam show that the distribution of solar radiation varies with season obviously. The difference of solar radiation between left and right bank is more than 100W/m2 . The good agreement of the data measured in situ with the computational result validates the effectiveness of the new method. The analysis results show that the daily average solar radiation is mostly composed of direct solar radiation. The radiation intensity of dam surface radiation depends on the orientation of the arch dam and the distribution of radiation depends on the combination of the orientation and latitLlde.