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arXiv 2103.09454physics.flu-dyn
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具有流向宽度变化的Hele-Shaw盒中扩散和拉平重力流的形状

Shape of spreading and leveling gravity currents in a Hele-Shaw cell with flow-wise width variation

Zhong Zheng, Aditya A. Ghodgaonkar, Ivan C. Christov

摘要:

我们研究的扩展和平整的重力流在一个Hele-Shaw细胞与流向宽度的变化作为一个模拟流{在裂缝和水平非均质含水层}。使用相平面分析,我们得到第二类自相似的解决方案来描述的重力流的形状的演变过程中的扩展(前封闭)和调平(后封闭)制度。的自相似理论相比,偏微分方程的数值模拟的演变电流的形状(润滑近似下)和桌面实验。具体而言,从润滑理论的控制偏微分方程的模拟允许我们计算的前因子,这是任意的\textit{a priori}在第二类自相似变换,通过估计所需的时间,电流进入自相似制度。与此前因子计算,我们表明,理论,模拟和实验吻合良好的传播前附近。在调平机制中,电流的记忆重置,并且在调整时间之后出现另一种自相似行为,我们从模拟中估计。再次,与前因子计算,模拟和实验都服从预测的自相似标度。对于前和后封闭制度,我们提供了详细的渐近(分析)表征的普遍电流分布出现的自相似性的第二种。

英文摘要:

We study the spreading and leveling of a gravity current in a Hele-Shaw cell with flow-wise width variations as an analog for flow {in fractures and horizontally heterogeneous aquifers}. Using phase-plane analysis, we obtain second-kind self-similar solutions to describe the evolution of the gravity current's shape during both the spreading (pre-closure) and leveling (post-closure) regimes. The self-similar theory is compared to numerical simulations of the partial differential equation governing the evolution of the current's shape (under the lubrication approximation) and to table-top experiments. Specifically, simulations of the governing partial differential equation from lubrication theory allow us to compute a pre-factor, which is \textit{a priori} arbitrary in the second-kind self-similar transformation, by estimating the time required for the current to enter the self-similar regime. With this pre-factor calculated, we show that theory, simulations and experiments agree well near the propagating front. In the leveling regime, the current's memory resets, and another self-similar behavior emerges after an adjustment time, which we estimate from simulations. Once again, with the pre-factor calculated, both simulations and experiments are shown to obey the predicted self-similar scalings. For both the pre- and post-closure regimes, we provide detailed asymptotic (analytical) characterization of the universal current profiles that arise as self-similarity of the second kind.

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