Mixing, entrainment and energetics of gravity currents released from two-layer stratified locks
Mixing, entrainment and energetics of gravity currents released from two-layer stratified locks
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DOI：
10.1017/jfm.2023.146
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发表时间：
2023-03
影响因子：
3.7
通讯作者：
R. Zhu;Zhiguo He;E. Meiburg
中科院分区：
文献类型：
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作者：
R. Zhu;Zhiguo He;E. Meiburg
摘要用三维直接数值模拟方法研究了双层层状水闸中重力流的混合、卷吸和能量收支。根据密度和层厚比，我们发现上层或下层流体可以更快地传播，整个重力流的密度结构可以从强烈分层到接近完全混合。此外，我们还观察到密度比的中间值可以最大化重力流层之间的混合。在涡度预算的基础上，我们提出了一个理论模式，用于预测下层比上层移动得更快的两层的总重力流高度和锋面速度。该模型确定了高度比和厚度比在确定水流速度结构中的作用，并阐明了环境逆流的动力学。对能量收支的详细分析量化了势能到动能的转换作为控制参数的函数，以及重力流和周围流体不同层之间的能量转移。根据密度和层厚比的值，我们发现下层锁定层可以获得或损失能量，而上层总是损失能量。
Abstract We conduct three-dimensional direct numerical simulations to investigate the mixing, entrainment and energy budgets of gravity currents emerging from two-layer stratified locks. Depending on the density and layer thickness ratios, we find that either the upper layer or lower layer fluid can propagate faster, and that the density structure of the overall gravity current can range from strongly stratified to near-complete mixing. We furthermore observe that intermediate values of the density ratio can maximise mixing between the gravity current layers. Based on the vorticity budget, we propose a theoretical model for predicting the overall gravity current height, along with the front velocity of the two layers, for situations in which the lower layer moves faster than the upper layer. The model identifies the role of the height and thickness ratios in determining the velocity structure of the current, and it clarifies the dynamics of the ambient counter-current. A detailed analysis of the energy budget quantifies the conversion of potential into kinetic energy as a function of the governing parameters, along with the energy transfer between the different layers of the gravity current and the ambient fluid. Depending on the values of the density and layer thickness ratios, we find that the lower lock layer can gain or lose energy, whereas the upper layer always loses energy.