Abstract An experimental study has been performed by using particle image velocimetry to investigate the effect of nozzle-to-plate separation distance ( L ) and jet impingement angle on the flow characteristics of an obliquely inclined submerged water jet. Measurements were taken for L = 1 D , 2 D , 4 D and 6 D (where D is the diameter of the nozzle) for the jet impingement angle ( θ ) of 45° and 26°, and the flow characteristics in the uphill and the downhill regions are investigated at Reynolds number of 2600 (based on the nozzle diameter D and the jet velocity $$U_{{\text{o}}}$$ U o ). It is observed that surface spacing has an opposite effect in the uphill and the downhill regions in terms of wall jet flow. In the uphill region, the tendency of the wall jet to grow increases with increase in L / D . However, in the downhill region, the jet velocity and its thickness are observed to reduce as the separation distance is increased. The distance between the stagnation point and the geometric centre is observed to decrease with increase in L / D because of jet–ambient fluid interaction in the uphill region. The jet width is observed to grow for θ = 45° in the downstream of the plate due to enhanced jet–ambient fluid interaction. Flow at θ = 26° shows that after impingement the entire jet deviates towards the downhill side, which indicates the existence of a critical impingement angle below which there is no flow of the jet in the uphill region. RMS velocity fluctuations and shear stress show an increased turbulence level downstream of the plate in the downhill region for smaller impinging distance implying higher jet–ambient fluid interaction and increased jet width. They, along with the negative turbulence production term, reveal the region of flow separation and reattachment. The decrease in the peak value of Nusselt number can be related to the drop in the jet momentum at the stagnation point with increase in the surface spacing. Graphic abstract

中文翻译：

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斜射流流动特性的实验研究

摘要 使用粒子图像测速法进行了实验研究，研究了喷嘴到板的间隔距离（L）和射流冲击角对倾斜水下水射流流动特性的影响。对 L = 1 D 、2 D 、4 D 和 6 D（其中 D 是喷嘴的直径）进行了测量，射流撞击角 ( θ ) 为 45° 和 26°，以及上坡和上坡的流动特性。在雷诺数为 2600（基于喷嘴直径 D 和射流速度 $$U_{{\text{o}}}$$U o ）下研究下坡区域。观察到表面间距在壁面射流方面在上坡和下坡区域具有相反的影响。在上坡区域，壁射流的增长趋势随着 L / D 的增加而增加。然而，在下坡地区，观察到射流速度及其厚度随着分离距离的增加而降低。由于上坡区域的射流-环境流体相互作用，观察到驻点和几何中心之间的距离随着 L / D 的增加而减小。由于增强的射流-环境流体相互作用，观察到射流宽度在板的下游随着 θ = 45° 增长。θ = 26° 处的流动表明撞击后整个射流偏向下坡侧，这表明存在临界撞击角，低于该角度时，上坡区域没有射流流动。RMS 速度波动和剪切应力显示，下坡区域板块下游的湍流水平增加，撞击距离更小，这意味着射流 - 环境流体相互作用更高，射流宽度增加。他们，连同负湍流产生项，揭示流动分离和再附着的区域。Nusselt 数峰值的降低可能与滞点处射流动量随着表面间距的增加而下降有关。图形摘要