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首页> 外文期刊>The European physical journal, E. Soft matter >Low Reynolds number suspension gravity currents
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Low Reynolds number suspension gravity currents

机译：低雷诺数悬浮重力流

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The extension of a gravity current in a lock-exchange problem, proceeds as square root of time in the viscous-buoyancy phase, where there is a balance between gravitational and viscous forces. In the presence of particles however, this scenario is drastically altered, because sedimentation reduces the motive gravitational force and introduces a finite distance and time at which the gravity current halts. We investigate the spreading of low Reynolds number suspension gravity currents using a novel approach based on the Lattice-Boltzmann (LB) method. The suspension is modeled as a continuous medium with a concentration-dependent viscosity. The settling of particles is simulated using a drift flux function approach that enables us to capture sudden discontinuities in particle concentration that travel as kinematic shock waves. Thereafter a numerical investigation of lock-exchange flows between pure fluids of unequal viscosity, reveals the existence of wall layers which reduce the spreading rate substantially compared to the lubrication theory prediction. In suspension gravity currents, we observe that the settling of particles leads to the formation of two additional fronts: a horizontal front near the top that descends vertically and a sediment layer at the bottom which aggrandises due to deposition of particles. Three phases are identified in the spreading process: the final corresponding to the mutual approach of the two horizontal fronts while the laterally advancing front halts indicating that the suspension current stops even before all the particles have settled. The first two regimes represent a constant and a decreasing spreading rate respectively. Finally we conduct experiments to substantiate the conclusions of our numerical and theoretical investigation. Graphical abstract: [Figure not available: see fulltext.]
机译：锁定交换问题中重力流的扩展在粘性浮力阶段中作为时间的平方根进行，其中重力和粘性力之间达到平衡。但是，在存在颗粒的情况下，这种情况会发生很大的变化，因为沉淀会降低原动力，并引入重力流停止的有限距离和时间。我们使用基于莱迪思-玻耳兹曼（LB）方法的新方法研究低雷诺数悬浮重力流的传播。将悬浮液建模为具有浓度依赖性粘度的连续介质。使用漂移通量函数方法模拟了颗粒的沉降，该方法使我们能够捕获以运动冲击波传播的颗粒浓度突然间断。此后，对不等粘度的纯流体之间的交换交换流动进行了数值研究，结果表明，与润滑理论的预测相比，存在着许多壁层，这些壁层大大降低了扩散速率。在悬浮重力流中，我们观察到颗粒的沉降导致形成两个附加的前沿：顶部附近的水平前沿垂直下降，底部的沉积层由于颗粒的沉积而增大。在扩散过程中确定了三个阶段：最后一个阶段对应于两个水平前沿的相互接近，而横向前进的前沿停止，表明悬浮电流甚至在所有颗粒沉降之前就停止了。前两个方案分别表示一个常数和一个递减的扩展速率。最后，我们进行实验以证实我们的数值和理论研究的结论。图形摘要：[该图不可用：请参见全文。]

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