低浓度盐水异重流运动规律试验研究

Experimental study on movement characters of low concentration saline density current

船舶通过河口船闸将导致盐水潜入闸室继而侵入淡水河道造成水质恶化。既有研究集中于海船闸高浓度盐水入侵(浓度20‰~30‰),但对于河口船闸低浓度盐水(浓度2.23‰~4.17‰)入侵过程及规律尚不清楚。基于室内大尺度水槽试验,研究了低浓度盐水的运动特性,探讨低浓度盐水运动形态的演变过程、盐度分布与盐水运动形态的关系、盐水头部运动速度以及密度弗劳德数与浓度的关系。结果表明,受密度梯度力驱动,低浓度盐水仍然作异重流运动并集中在底部输移;低浓度盐水异重流运动形态的转化距离相比高浓度盐水更远,其运动状态受底床阻力影响分为滑塌阶段和自相似阶段,密度弗劳德数在滑塌阶段为常数(Fr_(H)=0.32)、自相似阶段随时间线性递减(斜率为-0.01)。

Ships passing through estuarine locks will cause salt water to sneak into the lock chamber and then invade the freshwater channel,causing water quality deterioration.Previous researches focused on the invasion of high concentration salt water(concentration 20‰-30‰)in sea locks,but the invasion process and characters of low concentration salt water intrusion(concentration 2.23‰-4.17‰)in estuarine locks are still unclear.Based on the large-scale water tank experiments,this paper studies the motion characteristics low concentration salt water and discusses the evolution process of low concentration salt water motion form,the relationship between salinity distribution and motion form,the motion velocity of salt water head,and the relationship between density Froude number and concentration.The results show that,driven by the density gradient force,the low concentration salt water still moves as a heterogeneous flow and concentrates at the bottom.The transformation distance of the heterogeneous flow form of low concentration salt water is farther compared with that of high concentration salt water,and its kinematic state can be divided into the sliding stage and self-similarity stage effected by the bottom-bed drag force.The density Froude number is constant in the sliding stage(Fr_(H)=0.32),and decreases linearly with time in the self-similarity stage(slope of-0.01).