渡槽水体的热交换及水温和含冰率的时空变化

渡槽是一种高架空中的输水建筑物，冰期易于形成产冰场，可能导致下游发生冰塞灾害。考虑渡槽外壁与大气的热交换，包括太阳辐射、外壁和大气的长波辐射、地表的长波辐射和反射及对流等因素，提出了渡槽外壁温度及水体与渡槽热交换的计算模型。建立了冰期渡槽水温时空变化的一维数学模型，采用特征线方法得出水温随时间和离开渡槽进口距离的增加呈指数规律变化的重要结论。在此基础上，导出了渡槽含冰率与负水温成正比的理论公式。算例表明，如果忽视水体与渡槽的热交换，则可能导致计算冰情远远偏离实际情况的结果。

Heat exchange of water and spatial-temporal variation of water temperature and ice content in aqueduct

Aqueduct is an elevated water conveyance structure. It is easy to form an ice field during the ice period, which may lead to ice jam disaster in the downstream. Considering the heat exchange between the outer wall of the aqueduct and the atmosphere, including solar radiation, long wave radiation, reflection and convection on the surface, the models for calculating the outer wall temperature of the aqueduct and the heat exchange between water and the aqueduct are proposed. A one-dimensional mathematical model of the temporal and spatial variation of water temperature in the aqueduct during the ice period is established. The important conclusion that the water temperature changes exponentially with time and the increase of the distance from the aqueduct inlet is obtained by using the characteristic line method. On this basis, the theoretical formula that the ice content of aqueduct is directly proportional to the negative water temperature is derived. The example shows that if the heat exchange between water and aqueduct is ignored, the calculated ice condition may deviate from the actual situation.