排污流速比对河流水体中悬浮物沉降和底泥再悬浮的影响

采用数值模拟和水槽试验相结合的方法,研究河道排污口不同排污流速比(R分别为4.5、7.2和9.9)对悬浮物在排污口下游区域沉降和底泥再悬浮的影响。结果表明:随着流速比的增加,紊动越剧烈,污染云团扩散范围越大,沉降和悬浮作用也越明显。不同流速比情况下,通过底部水平面的沉降通量变化趋势基本一致,即先增加、后稳定,通量总量随着流速比增大而增加;由于临界起动流速(对应于R=5.8)的存在导致低流速比(R=4.5)情况下再悬浮通量增长缓慢,而中流速比(R=7.2)和高流速比(R=9.9)情况下再悬浮通量增长迅速。由此可见,排污流速对排污口下游区域悬浮物的沉降和底泥再悬浮具有重要的影响。

Impact of discharge velocity ratio of sewage outlet on sedimentation of suspended solids and resuspension of sediments in river

Based on numerical simulations and flume experiments, the processes of sedimentation of suspended solids and resuspension of sediments in the region downstream of a sewage outlet in a river were analyzed at three velocity ratios(R=4. 5, 7. 2, and 9. 9, where R is the ratio of discharge velocity at the sewage outlet to the flow velocity in the river). Results show that the relative turbulence intensity and the area of the pollution zone increased with the velocity ratio; this also resulted in significant sedimentation of suspended solids and resuspension of sediments in the river. At the three velocity ratios, the sedimentation fluxes of suspended solids through the bottom horizontal plane have similar distributions: first increasing and then reaching respective stable values; and the total fluxes of suspended solids increased with the velocity ratio. At a low velocity ratio(R=4. 5), the resuspension fluxes of suspended solids increased slowly due to the existence of a critical incipient velocity(corresponding to R=5. 8), while at the medium velocity ratio(R=7. 2)and high velocity ratio(R=9. 9), the resuspension fluxes increased rapidly. As a result, the discharge velocity of the sewage significantly affected the sedimentation of suspended solids and resuspension of sediments in the region downstream of the outlet.