Gravity currents from moving sources
Gravity currents from moving sources
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DOI：
10.1017/jfm.2021.654
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发表时间：
2021-08-17
影响因子：
3.7
通讯作者：
Peacock, Thomas
中科院分区：
文献类型：
--
作者：
Ouillon, Raphael;Kakoutas, Christos;Peacock, Thomas
深海采矿和地球工程等新兴技术对重力流动力学提出了全新的问题。这些活动可从移动的地点不断释放密集的沉积物羽流，然后作为重力流传播。在这里，我们提出了这种新的配置的理想化的数值模拟的结果，并调查的重力流的传播，结果从一个移动的浮力源，作为一个函数的源速度浮力速度的比率。我们表明，在该比率的一定值以上，流动进入超临界状态，其中源的移动速度比产生的电流更快，从而在移动源的参考系中产生统计稳定状态。一旦在超临界状态下，电流通过第二个过渡，超过该过渡，流体在头部的电流移动的方向大致垂直于源的运动方向，以及在横向方向上的前端的时间演化是很好地描述了一个等效的恒定体积锁定释放重力流。我们利用我们的研究结果来深入了解深海采矿收集器车辆释放的沉积物羽流的传播，并提出了一个模型深海采矿收集器在其尾流中排放致密染色流体的概念验证拖车实验室实验。实验结果表明，重力流前缘呈楔形，随着收集器与浮力速度之比的增大，前缘变窄。在超临界状态下，时间平均前沿位置与数值模型的结果吻合得很好。
Emerging technologies such as deep-sea mining and geoengineering pose fundamentally new questions regarding the dynamics of gravity currents. Such activities can continuously release dense sediment plumes from moving locations, thereafter propagating as gravity currents. Here, we present the results of idealized numerical simulations of this novel configuration, and investigate the propagation of a gravity current that results from a moving source of buoyancy, as a function of the ratio of source speed to buoyancy velocity. We show that above a certain value of this ratio, the flow enters a supercritical regime in which the source moves more rapidly than the generated current, resulting in a statistically steady state in the reference frame of the moving source. Once in the supercritical regime, the current goes through a second transition beyond which fluid in the head of the current moves approximately in the direction normal to the direction of motion of the source, and the time evolution of the front in the lateral direction is well described by an equivalent constant volume lock-release gravity current. We use our findings to gain insight into the propagation of sediment plumes released by deep-sea mining collector vehicles, and present proof-of-concept tow-tank laboratory experiments of a model deep-sea mining collector discharging dense dyed fluid in its wake. The experiments reveal the formation a wedge-shaped gravity current front which narrows as the ratio of collector-to-buoyancy velocity increases. The time-averaged front position shows good agreement with the results of the numerical model in the supercritical regime.