Numerical evidence of an undisturbed region of flow in a turbulent rectangular submerged free jet
Numerical evidence of an undisturbed region of flow in a turbulent rectangular submerged free jet
复制标题
DOI：
10.1080/10407782.2016.1139986
复制
发表时间：
2016-05
期刊：
影响因子：
--
通讯作者：
A. Boghi;M. Angelino;F. Gori
中科院分区：
文献类型：
--
作者：
A. Boghi;M. Angelino;F. Gori
摘要 文献中通过存在两个流动区域来描述湍流矩形浸没自由射流的演化：潜在核心区域（PCR）和完全发展区域（FDR）。然而，过去十年进行的实验表明，存在第三个流动区域，即平均可视化中所谓的无扰动流动区域（URF），或即时可视化中所谓的可忽略扰动流动（NDF）加上小扰动流动（SDF）。 URF 位于时隙出口和 PCR 开头之间。 URF 和 NDF 的主要特征是速度和湍流分布几乎与狭缝出口处测量的相同，并且射流高度保持与狭缝高度相同。在 SDF 中，射流高度发生微小变化，即收缩或膨胀，但不会形成涡流。迄今为止，文献还没有给出 URF 存在的数字证据。本研究涉及二维射流，提出了在四个雷诺数下进行的大涡模拟 (LES)，该模拟能够预测和表征 URF。将当前的数值结果与之前的理论方法进行比较，并确认槽出口和 PCR 之间存在 URF。此外，URF具有自相似行为，并提出了新的动量演化定律。
ABSTRACT The evolution of turbulent rectangular submerged free jets is described in the literature by the presence of two regions of flow: the potential core region (PCR) and the fully developed region (FDR). However, experiments carried out in the last decade showed that a third region of flow is present, the undisturbed region of flow (URF), so-called in the average visualization, or the negligible disturbances flow (NDF) plus the small disturbances flow (SDF), so-called in the instant visualization. The URF is located between the slot exit and the beginning of the PCR. The main characteristics of URF, and NDF, are that velocity and turbulence profiles remain almost equal to those measured on the slot exit, and the height of the jet remains equal to the slot one. In the SDF the jet height undergoes small variations, i.e., contractions or expansions, but without formation of the vortex. To date, no numerical evidence of the presence of URF has been given by the literature. The present study, which concerns a two-dimensional jet, presents Large Eddy Simulations (LES), carried out at four Reynolds numbers, which are able to predict and characterize URF. The present numerical results are compared to previous theoretical approaches and confirm the presence of URF, between the slot exit and the PCR. Moreover, URF has a self-similar behavior and a new law for the evolution of the momentum is proposed.