水质模型中污染物衰减系数敏感性分析

对于河流纳污能力数值模拟问题,污染物扩散衰减系数是一个重要参数,决定了模型的准确性和可靠性。本文针对三峡大坝至葛洲坝之间河段,基于Mike21建立平面二维水质模型,以氨氮为典型污染物分析河流纳污能力,在此基础上进行了衰减系数对流量、本底浓度及有无衰减过程等因素的敏感性分析。模拟结果表明:相比本底浓度,流量的改变对污染物扩散过程的影响更为明显;污染物扩散范围随流量的增加而增加,随本底浓度的增大而降低;增大衰减系数将使污染物扩散范围减小,且高流量低本底浓度时衰减系数的取值范围较大,使得影响范围变幅最大。

Sensitivity analysis of pollutant decay coefficient in water quality model

Decay factor is very important for numerical simulation of the assimilative capacity for a river, because it determines the accuracy and reliability of the water quality model. Based on Mike21, a two dimensional water quality model was established to analyze the assimilative capacity of the typical river breach between the Three Gorges Dam and the Gezhouba Dam. Ammonia nitrogen was chosen as the typical pollutant. Sensitivity analysis was performed by changing the discharge, background concentration of the pollutant and decay factor. The simulation results show that: Compared with the background concentration, the change of discharge has a more obvious effect on the pollutant diffusion process. The diffusion range of pollutant increased with the increase of discharge and decreased with the increase of background concentration of the pollutant. Increasing the decay coefficient will reduce the range of pollutant diffusion, and the range of decay coefficient will be larger when the discharge is high and the background concentration of the pollutant is low, which makes the range of influence maximum.