Confined plunging jets are investigated as potential outfalls for the discharge of desalination brine. Compared to offshore submerged outfalls that rely on momentum to induce mixing, plunging jets released above the water surface utilize both momentum and negative buoyancy. Plunging jets also introduce air into the water column, which can reduce the possibility of hypoxic zones. In contrast to unconfined plunging jets, confined plunging jets include a confining tube, or downcomer, around the jet, which increases the penetration depth of the bubbles and can provide better aeration. However, the presence of this downcomer can hinder mixing with surrounding water. Therefore, laboratory measurements of dilution are reported here and compared to the dilution of unconfined plunging jets. In addition, qualitative observations of bubble penetration depth are also used to discuss aeration potential. For designs that increase the bubble penetration depth as compared to unconfined plunging jets, results show that dilution decreases as the depth of the downcomer is increased. However, it is shown that confined plunging jets can be designed with a short downcomer to provide higher dilution than unconfined jets. The effect of the diameter of downcomer on dilution is also investigated and a non-monotonic effect is observed.

中文翻译：

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密闭柱塞式液体喷射器，用于淡化海水淡化厂中的盐水

对受限的急流喷嘴进行了研究，以作为脱盐盐水排放的潜在排放口。与依靠动量引起混合的近海淹没排泄口相比，在水面以上释放的急流喷射既利用了动量又产生了负浮力。柱塞式射流还将空气引入水柱，这可以减少缺氧区域的可能性。与无限制的插入式射流相反，受限的插入式射流包括围绕射流的限制管或降液管，这增加了气泡的穿透深度并可以提供更好的充气。但是，该降液管的存在会阻碍与周围水的混合。因此，此处报告了实验室对稀释度的测量结果，并将其与无侧限射流的稀释度进行了比较。此外，对气泡渗透深度的定性观察也用于讨论曝气潜能。对于与无限制插入式射流相比增加了气泡渗透深度的设计，结果表明，随着降液管深度的增加，稀释度降低。然而，已经表明，可以将受限的柱塞式射流设计成具有短的降液管，以提供比非受限的射流更高的稀释度。还研究了降液管直径对稀释的影响，并观察到了非单调的影响。结果表明，封闭式柱塞射流可以设计成具有短的降液管，以提供比无限制射流更高的稀释度。还研究了降液管直径对稀释的影响，并观察到了非单调的影响。结果表明，封闭式柱塞射流可以设计成具有短的降液管，以提供比无限制射流更高的稀释度。还研究了降液管直径对稀释的影响，并观察到了非单调的影响。