Unsteady turbulent round jets and vortex motion
Unsteady turbulent round jets and vortex motion
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DOI：
10.1063/1.2821910
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发表时间：
2007-12-01
影响因子：
4.6
通讯作者：
Reitz, Rolf D.
中科院分区：
文献类型：
--
作者：
Abani, Neerav;Reitz, Rolf D.
作为定常射流理论的推广，本文提出了一个新的模型来预测具有时变喷射剖面的圆形射流中的速度分布。该方法引入了一个有效的喷射速度的基础上的代表性的响应时间。假设瞬时喷射速度以指数响应函数影响射流内的速度，并且响应时间与射流内的流体颗粒的停留时间有关，这与来自Helmholtz的涡流运动分析的射流涡流环平移理论一致[P.G. Tait，伦敦爱丁堡都柏林Philos. Mag. J. Sci. 33，485（1867）]。Helmholtz理论也被证明是减少到众所周知的速度衰减率的情况下，稳定的湍流气体射流。一个Duhamel叠加积分是用来确定随时间变化的注射速率的有效注射速度。该模型进行了测试与不同的注入剖面和不同的环境密度。计算流体动力学代码的数值结果进行了比较。比较同意非常好，新的模型被证明是一个有效的方法来预测非定常射流射流尖端穿透。(c)2007年，美国物理学会。
A new model to predict the velocity distribution in round jets with time-varying injection profiles has been formulated as an extension of steady jet theory. The approach introduces an effective injection velocity within the jet based on a representative response time. It is assumed that the instantaneous injection velocity affects the velocity within the jet with an exponential response function and that the response time is related to the fluid particle's residence time within the jet, consistent with the theory of translation of jet vortex rings from Helmholtz's vortex motion analysis [P. G. Tait, London Edinburgh Dublin Philos. Mag. J. Sci. 33, 485 (1867)]. The Helmholtz theory is also shown to reduce to the well-known velocity decay rate in the case of steady turbulent gas jets. A Duhamel superposition integral is used to determine the effective injection velocity for time-varying injection rates. The model is tested with different injection profiles and different ambient densities. The results are also compared with numerical results from a computational fluid dynamics code. The comparisons agree very well and the new model is shown to offer an efficient method to predict jet tip penetrations for unsteady jets. (c) 2007 American Institute of Physics.