低含沙量异重流运动规律及其对水温分布的影响

The motion law of the density current with low sediment content and influence on water temperature distribution

当挟沙水流进入清水时,在特定的条件下会潜入底部向前运动,形成浑水异重流。水库水温分层使得水体密度在垂向出现差异,低含沙量浑水形成的异重流与周围水体密度接近,因而在运动过程中会受到垂向温度分层的干扰。浑水异重流是泥沙运动的特殊形式,还可能改变环境水体的温度,是水库调水调沙必须考虑的因素。该文应用水槽试验结合数值模拟,探究了水温分层条件下低含沙量异重流的运动规律及其对水温分布的影响。结果表明,异重流潜入点处形成回流,交界面以下含沙量以均匀梯度增加,前锋运动速度沿程不变;中层异重流不改变水温分布,而底层异重流则会对水温结构造成破坏,使得水温分布由分层型转变为混合型。

When silt carrying flow met clear water, it would dive into the bottom and keep on moving under certain conditions, such phenomenon is named as density current. The density of water is different in the vertical direction as a result of the vertical water temperature stratification. When turbidity current with low sediment concentration occurs, it will be disturbed, because its density is close to environmental water. Such flow is a special form of sediment transport, and it may change the temperature of environmental water. Therefore, it nmst be considered for the water-sediment regulation of reservoirs. This research used model experiment and computational fluid dynamics to study the motion law and influence on water temperature distribution of turbid density current. The results showed that reverse current occurred when diving, the sediment concentrationincreased at a uniform gradient and the velocity of forward movement was constant. Furthermore, the mid-layer density current didn＇t change the water temperature distribution, however the low-layer density current could make the water temperature structure from stratified type to mixed type.