采用离散坐标法计算一维平行入射辐射问题

针对离散坐标法难以应用于平行入射辐射的问题，提出了一种简单有效的方法；在原有的离散坐标系列中，直接添加一个与平行入射辐射的方向重合的离散方向，并将该离散方向的加权取得极其微小（合如1）10^-200)，这一新的离散方向对于离散坐标系列的各阶段矩方程没有任何影响，因此可以任意地设置，这样无论平行入射辐射来自哪个方向，都可以被准确地捕捉到，并采用一个一维大气辐射问题对本方法进行了检验，计算结果与精确解吻合。

Solving 1-D collimated irradiation problems by the discrete ordinate method

In order to eliminate the obstacle from the application of the discrete ordinates method to the collimated irradiation problems, a simple but effective method is proposed. It is recommended that a new discrete direction be added directly to an existing discrete ordinate quadrature set and the weight associated with this new discrete direction be set infinitely small. This new direction will exert no influence on the moment equations of the quadrature set and therefore it may be arbitrarily adjusted. In this way, no matter which direction the collimated beam comes from, it can always be captured. The method has been tested on the atmospheric radiation problem, the theoretical predictions are in good agreement with the precise solutions.