We perform numerical simulations to examine settling and fluid transport by a pair of particles passing through a thin density interface of a two-layer fluid. As the particles settle through the interface, they deform the interface and carry upper layer fluid into the lower layer. This increased buoyancy hinders the particle settling such that the trailing particle collides with the leading particle at strong stratification and when the particles are nearly vertically aligned. When descending into the lower layer, the upper layer fluid detaches from the particles, returning upward within a wake whose width is on the order of two particle diameters. Due to the added buoyancy and the returning wake, particle settling is hindered and the trailing particle separates away from the leading particle when aligned within or near the wake of the leading particle. Meanwhile, the trailing particle re-entrains fluid detached from the leading particle. Consequently, the transport of upper layer fluid into the lower layer increased by up to 40% in the case of weak stratification.

中文翻译：

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通过尖锐的，可混溶的密度界面沉降颗粒对

我们执行数值模拟，以检查通过两层流体的薄密度界面的一对颗粒的沉降和流体传输。当颗粒通过界面沉降时，它们使界面变形并将上层流体带入下层。这种增加的浮力阻碍了颗粒的沉降，使得在强分层时以及当颗粒几乎垂直排列时，尾随的颗粒与前导颗粒发生碰撞。当下降到下层时，上层流体从颗粒分离，并在尾流中向上返回，尾流的宽度约为两个粒径。由于增加了浮力和返回的尾波，当在前导颗粒的尾流内或附近对准时，阻碍了颗粒的沉降并且尾随的颗粒与前导颗粒分离。同时，尾随粒子重新夹带从前导粒子分离出的流体。因此，在弱分层的情况下，上层流体向下层的输送最多增加了40％。