Abstract In order to mitigate the effects of salt water intrusion at sea locks, bubble screens are installed which act as a barrier between the dense sea water and the fresh water inland. In order to optimize the design of the bubble screen, in this study a state-of-the-art numerical model is developed based on the Euler-Lagrange CFD method which is expanded with a simple salt balance and concentration-density coupling. The model has been validated by means of experimental results on a laboratory-scale bubble screen. The liquid circulation and entrainment have been investigated for two types of bubble injection methods. It is found that the bubble screen is successful as a separator of salt and fresh water in an initial period of τ s e p = 30 seconds but acts more as a mixer at later times due to the swaying of the screen. The rate of the mixing increases with the air flow rate. Two mechanisms of salt intrusion are distinguished; a delayed density current along the bottom and entrained liquid being circulated through the domain back to the screen. An optimum in air flow rate is found at a Froude air number F r a i r = 0.91 . Bubble screen behaviour is also checked at the lock-scale using lock-scale geometry and simulations. The amount of salt transmitted agrees well with the large-scale field tests up until the reported Frair numbers but Frair > > 1 need to be tested to check for the optimum as found in the lab-scale tests.

中文翻译：

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用于减缓海闸盐入侵的气泡屏数值研究

摘要 为了减轻海水入侵对海闸的影响，安装了气泡筛网，作为密集海水和内陆淡水之间的屏障。为了优化气泡筛的设计，在本研究中，基于欧拉-拉格朗日 CFD 方法开发了最先进的数值模型，该方法扩展了简单的盐平衡和浓度-密度耦合。该模型已通过实验室规模气泡筛上的实验结果进行了验证。已经研究了两种气泡注入方法的液体循环和夹带。发现气泡筛网在 τ sep = 30 秒的初始阶段成功地作为盐和淡水的分离器，但由于筛网的摇摆，在以后的时间更多地充当混合器。混合速率随着空气流速而增加。盐入侵的两种机制是不同的；沿着底部的延迟密度电流和夹带的液体通过域循环回到屏幕。在弗劳德空气数 F rair = 0.91 处发现空气流速的最佳值。还使用锁定比例几何和模拟在锁定比例检查气泡屏幕行为。传输的盐量与大规模现场测试一致，直到报告的 Frair 数，但需要测试 Frair > > 1 以检查实验室规模测试中发现的最佳值。在弗劳德空气数 F rair = 0.91 处发现空气流速的最佳值。还使用锁定比例几何和模拟在锁定比例检查气泡屏幕行为。传输的盐量与大规模现场测试一致，直到报告的 Frair 数，但需要测试 Frair > > 1 以检查实验室规模测试中发现的最佳值。在弗劳德空气数 F rair = 0.91 处发现空气流速的最佳值。还使用锁定比例几何和模拟在锁定比例检查气泡屏幕行为。传输的盐量与大规模现场测试一致，直到报告的 Frair 数，但需要测试 Frair > > 1 以检查实验室规模测试中发现的最佳值。