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A Numerical and Experimental Investigation of High-Speed Liquid Jets - Their Characteristics and Dynamics.

机译：高速液体射流的数值和实验研究-其特性和动力学。

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A comprehensive understanding of high-speed liquid jets is required for theirintroduction into engine and combustion applications. Their transient nature, shortlifetime, unique characteristics and the inability to take many experimental readings, has inhibited this need. This study investigates the outflow of a high-speed liquid jet into quiescent atmospheric air. The key characteristics present are, a bow shock wave preceding the jet head, an enhanced mixing layer and the transient deformation of the liquid jet core. The outflow regime is studied in an experimental and numerical manner.In the experimental investigation, a high-speed liquid water jet is generated using the momentum exchange by impact method. The jet velocity is supersonic with respect to the impinged gaseous medium. The resulting jet speed is Mach 1.8. The jet is visualised with the use of shadowgraph apparatus. Visualisation takes place over a variety of time steps in the liquid jet's life span and illustrates the four major development stages. The stages progress from initial rapid core jet expansion to jet stabilisation and characteristic uniform gradient formation. The visualisation shows that at all stages of the jet's life it is axi-symmetric. One dimensional nozzle analysis and a clean bow shock wave indicate that the pulsing jet phenomenon can be ignored.In the numerical investigation, a time marching finite volume scheme is employed. The bow shock wave characteristics are studied with the use of a blunt body analogy. The jet at a specific time frame is considered a solid body. The jet shape is found to have an important influence on the shock position and shape. Analysis of the results indicates a shock stand-off similar to that seen in experimental observations and the prediction of shock data.The jet life span is modelled using a species dependent density model. The transient calculations reproduce the key jet shape characteristics shown in experimental visualisation. The mushrooming effect and large mixing layer are shown to develop. These effects are strongest when the shock wave transience has yet to stabilise. Quantitative analysis of the mixing layer at varying time steps is presented.
机译：将高速液体射流引入发动机和燃烧应用需要对其有一个全面的了解。它们的瞬时性质，寿命短，独特的特性以及无法进行许多实验读数，已抑制了这种需求。这项研究调查了高速液体射流流入静态大气的情况。目前存在的主要特征是，在喷射头之前的弓形冲击波，增强的混合层和液体喷射芯的瞬时变形。通过实验和数值方法研究了流出状态。在实验研究中，利用冲击法的动量交换产生了高速液态水射流。射流的速度相对于撞击的气态介质是超音速的。产生的喷射速度为1.8马赫。使用皮影仪将喷流可视化。可视化发生在液体射流的使用寿命中的各个时间段上，并说明了四个主要的开发阶段。从最初的快速岩心射流扩展到射流稳定和特征均匀的梯度形成，这些阶段就开始了。可视化显示，在射流寿命的所有阶段，它都是轴对称的。一维喷嘴分析和干净的弓形冲击波表明可以忽略脉冲喷射现象。在数值研究中，采用了时间行进有限体积方案。船首冲击波的特性是通过使用钝体类比来研究的。在特定时间范围内的射流被认为是固体。发现射流形状对冲击位置和形状具有重要影响。对结果的分析表明，与实验观察和冲击数据的预测相似，其冲击距离很短。射流寿命是通过物种依赖性密度模型来建模的。瞬态计算再现了实验可视化中显示的关键射流形状特征。出现了蘑菇效应和较大的混合层。当冲击波瞬态尚未稳定时，这些效果最强。给出了在不同时间步长下混合层的定量分析。

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