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首页> 外文期刊>Experiments in Fluids: Experimental Methods and Their Applications to Fluid Flow >Laser-Doppler measurements of impinging jet flows through a crossflow
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Laser-Doppler measurements of impinging jet flows through a crossflow

机译：激光多普勒测量穿过横流的射流

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摘要

The flowfield resulting from the impingement of a single axisymmetric jet against a wall after penetrating a confined crossflow has been studied experimentally using laser-Doppler anemometry. For sufficiently high jet velocities and small distances between the jet exit and the ground plane to produce impingement, two regions of the flow are seen to be of particular interest: the impinging region and the ground vortex caused by the interaction between the upstream wall jet and the crossflow. The latter consists of a vortical structure that wraps around the impinging jet like a scarf and should develop further downstream through a pair of streamwise vortices. The present work reports a study aimed at characterising the influence of the jet-to-crossflow velocity ratio on the structure of the ground vortex. The experiments were performed for Reynolds numbers based on the jet exit conditions of between 60,000 and 105,000 corresponding to jet-to-crossflow velocity ratios from 30 to 73 and for an impinging height of five jet diameters. The shape, size and location of the ground vortex were found to be dependent on the velocity ratio, and two different regimes were identified. For the higher velocity ratio regime, the downstream wall jet it is not strongly affected by the ground vortex, and the velocity profiles become similar. In both regimes, the crossflow acceleration over the ground vortex was found to be directly connected with the jet exit velocity. This indicates that the influence of the upstream wall jet is not confined to the ground vortex but spreads until the upper wall by a mechanism that needs further investigation.
机译：使用激光多普勒风速计，已经对通过有限的横流穿透后单个轴对称射流撞击壁所产生的流场进行了实验研究。对于足够高的射流速度和射流出口与地面之间的小距离以产生撞击，特别要注意两个流动区域：上游壁射流和射流之间的相互作用引起的撞击区域和地面涡流。横流。后者由涡流结构组成，该涡流结构像围巾一样包裹着撞击的喷流，并应通过一对沿流的涡流进一步向下游发展。本工作报告了一项旨在表征射流与横流速度比对地面涡旋结构影响的研究。根据在60,000和105,000之间的射流出口条件（对应于30至73的射流与横流速度比）和5个射流直径的撞击高度，对雷诺数进行了实验。发现地面涡流的形状，大小和位置取决于速度比，并确定了两种不同的状态。对于更高的速比范围，下游涡流不受地面涡流的强烈影响，速度分布变得相似。在这两种情况下，都发现地面涡流上的横流加速度与射流出口速度直接相关。这表明上游壁面射流的影响并不局限于地面涡流，而是通过需要进一步研究的机制传播到上壁。

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