A novel pre-dilution, swirling jet diffuser to enhance effluent mixing: Hydrodynamics and dilution performance

IF 2.4 3区 环境科学与生态学 Q2 ENGINEERING, CIVIL Journal of Hydro-environment Research Pub Date : 2022-11-01 DOI:10.1016/j.jher.2022.08.002
Xinzai Peng , Yiying He , Yijun Zhao , Wenming Zhang
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Abstract

Diffusers are widely-used to quickly dilute effluents in receiving water bodies. This study proposed a novel diffuser that pre-mixes effluent with ambient water before discharging and that uses the swirling jet to further enhance near-field dilution. The nozzle of the diffuser was examined in two ambient flow conditions: co-flow and counter-flow that are commonly-met in the environment such as oceans due to tidal effect. Physical experiments were first conducted in co-flow on its dilution performance and hydrodynamics, using heated water as the effluent. A 3-D CFD model was developed and calibrated the co-flow scenarios, and then used to investigate the diffuser in counter-flow. The results showed that the nozzle can effectively reduce the maximum temperature rise of the effluent by about 50 % before discharging. The swirling jet from the outlet has a larger shear area, half-width and entrainment rate, enabling the effluent to be rapidly diluted to a minimum of around 10 times at x/D = 6 in co-flow, whereas the dilution for conventional nozzles is about 1 because of the potential core. The flow amplification ratio (α) decreases gradually with increasing velocity ratio in co-flow but increases with increasing velocity ratio in counter-flow. The counter-flow reduces the water drawn into the device; however, the pre-dilution effect at the outlet remains stable. The near-field dilution in counter-flow was significantly enhanced than that in co-flow. Environmental regulations at outfalls and mixing zones can be more easily met using this novel diffuser.

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一种新型的预稀释旋流射流扩散器,用于增强出水混合:流体动力学和稀释性能
扩散器被广泛用于快速稀释接收水体中的污水。本研究提出了一种新型扩散器,该扩散器在排放前将污水与环境水预混合,并利用旋流射流进一步增强近场稀释。对扩散器喷嘴进行了共流和逆流两种环境流动条件下的测试,这两种流动条件在海洋等环境中由于潮汐效应而常见。首先在共流条件下,以热水为流出物,对其稀释性能和流体力学特性进行了物理实验。建立了三维CFD模型,对共流场景进行了标定,并应用该模型对逆流中的扩压器进行了研究。结果表明,该喷嘴可有效降低排放前出水的最高温升约50%。出口的旋流射流具有更大的剪切面积、半宽和夹带速率,在x/D = 6的共流条件下,出水可以被快速稀释到至少10倍左右,而传统喷嘴由于潜在核心的影响,稀释率约为1。流动放大比(α)在共流中随流速比的增大而逐渐减小,在逆流中随流速比的增大而增大。逆流减少了进入装置的水;但在出口处的预稀释效果保持稳定。逆流时的近场稀释比共流时明显增强。使用这种新型扩散器可以更容易地满足出口和混合区的环境要求。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Journal of Hydro-environment Research
Journal of Hydro-environment Research ENGINEERING, CIVIL-ENVIRONMENTAL SCIENCES
CiteScore
5.80
自引率
0.00%
发文量
34
审稿时长
98 days
期刊介绍: The journal aims to provide an international platform for the dissemination of research and engineering applications related to water and hydraulic problems in the Asia-Pacific region. The journal provides a wide distribution at affordable subscription rate, as well as a rapid reviewing and publication time. The journal particularly encourages papers from young researchers. Papers that require extensive language editing, qualify for editorial assistance with American Journal Experts, a Language Editing Company that Elsevier recommends. Authors submitting to this journal are entitled to a 10% discount.
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