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Experimental investigation into turbulent negatively buoyant jets using combined PIV and PLIF measurements
International Journal of Heat and Fluid Flow ( IF 2.6 ) Pub Date : 2020-04-01 , DOI: 10.1016/j.ijheatfluidflow.2020.108561
L. Milton-McGurk , N. Williamson , S.W. Armfield , M.P. Kirkpatrick

Abstract Turbulent negatively buoyant jets occur when the buoyancy of a jet opposes its source momentum. In these flows, the fluid will rise until it reaches a stagnation point and a return flow is established, forming a fountain ( Hunt and Burridge, 2015 ). This study looks at both the initial negatively buoyant jet stage of this flow, before the return flow has established, and the fully developed fountain stage. Two-dimensional particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF) are used to simultaneously measure the velocity and scalar concentration fields. An experimental and image processing procedure for the PLIF is introduced that accounts for pulse-to-pulse variations in laser power and beam profile for an Nd:YAG laser, which has been demonstrated to reduce the error in scalar concentration measurements. The flow is investigated experimentally using a 1m3 tank of salt-water ambient with freshwater + ethanol negatively buoyant jets, allowing for measurements to be taken at F r o = 30 and R e o = 5900 . The entrainment coefficient for a negatively buoyant jet has been estimated as α ≅ 0.054, lower than a neutral jet at α ≅ 0.058. A finding consistent with existing literature (Bloomfield and Kerr, 2000; McDougall, 1981).

中文翻译:

使用联合 PIV 和 PLIF 测量对湍流负浮力射流进行实验研究

摘要 当射流的浮力与其源动量相反时,就会出现湍流负浮力射流。在这些流动中,流体将上升,直到到达停滞点,并建立回流,形成喷泉(Hunt and Burridge, 2015)。本研究着眼于回流建立之前的初始负浮力喷射阶段和完全发展的喷泉阶段。二维粒子图像测速 (PIV) 和平面激光诱导荧光 (PLIF) 用于同时测量速度和标量浓度场。介绍了 PLIF 的实验和图像处理程序,该程序解释了 Nd:YAG 激光器的激光功率和光束轮廓的脉冲到脉冲变化,这已被证明可以减少标量浓度测量的误差。使用带有淡水 + 乙醇负浮力射流的 1 立方米盐水环境对流动进行实验研究,允许在 F ro = 30 和 R eo = 5900 下进行测量。负浮力射流的夹带系数估计为 α ≅ 0.054,低于 α ≅ 0.058 的中性射流。与现有文献一致的发现(Bloomfield 和 Kerr,2000 年;McDougall,1981 年)。
更新日期:2020-04-01
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