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.

扩散器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，可在排放前将流出物与环境水预混合，并使用旋流射流进一步增强近场稀释。在两种环境流动条件下检查了扩散器的喷嘴：由于潮汐效应而在海洋等环境中常见的顺流和逆流。物理实验首先在同流中对其稀释性能和流体动力学进行，使用热水作为流出物。开发了一个 3-D CFD 模型并校准了顺流场景，然后用于研究逆流中的扩散器。结果表明，该喷嘴可有效降低排放前出水最大温升约50%。x/D  = 6 在并流中，而传统喷嘴的稀释度约为 1，因为潜在的核心。流量放大比（α）随着顺流速度比的增加而逐渐减小，但随着逆流速度比的增加而增加。逆流减少了吸入设备的水；但是，出口处的预稀释效果保持稳定。逆流中的近场稀释比顺流中的近场稀释显着增强。使用这种新型扩散器可以更轻松地满足排放口和混合区的环境法规。