Conditional sampling of a high Péclet number turbulent plume and the implications for entrainment
Conditional sampling of a high Péclet number turbulent plume and the implications for entrainment
复制标题
高佩克莱数湍流羽流的条件采样及其对夹带的影响
DOI：
10.1017/jfm.2017.284
复制
发表时间：
2017
影响因子：
3.7
通讯作者：
Burridge H
中科院分区：
文献类型：
--
作者：
Burridge H
我们在轴对称纯湍流羽流的中心垂直平面上同时进行二维速度和标量测量。我们使用边缘检测算法来确定羽流的边缘，并比较在固定欧拉框架和相对于根据瞬时羽流边缘定义的局部坐标的框架中获得的数据。在欧拉框架中，我们观察到垂直和水平速度的时间平均分布是自相似的，垂直速度可以很好地用高斯分布表示。我们将这些测量的条件取决于流体是在羽流内部还是外部，以及内部流体是混合羽流流体还是被吞没的环境流体。我们发现，平均而言，总垂直体积传输的 5% 发生在羽流外部，而在大型相干结构之间的高度处，这一数字上升到近 14%。我们发现，羽流包络内被吞没流体的通量略大于羽流外部的垂直传输，这表明环境流体在被吞噬穿过湍流/非湍流界面（TNTI）之前被吞没到羽流包络中，然后最终不可逆地混合。我们在羽流坐标（跟随蜿蜒波动的羽流）中的新测量显示，羽流内和附近环境流体中的流动受到羽流内局部存在或不存在涡流的强烈影响。当存在涡流并且羽流很宽时，羽流边缘附近的垂直速度很小，因此所有垂直传输都在羽流内部。在羽流狭窄且没有涡流的区域中，在羽流外部观察到较大的垂直速度并因此发生传输，这表明与涡流相关的压力加速了环境流体，然后环境流体被吞没到羽流中。最后，我们表明，观察到羽流标量边缘之外的显着垂直速度并不表明速度分布的特征宽度大于标量场的特征宽度；相反，我们的观察结果表明，浮力分布比速度宽 20%。羽流坐标中的测量表明，羽流中动量的混合导致微分熵接近最大值的分布，并且动量的混合不受羽流 TNTI 的抑制（即不受限制）。此外，我们的测量表明，羽流中的标量混合也可能导致微分熵接近最大值的分布，但与动量相反，标量混合严格受羽流边缘限制。
We present simultaneous two-dimensional velocity and scalar measurements on a central vertical plane in an axisymmetric pure turbulent plume. We use an edge-detection algorithm to determine the edge of the plume, and compare the data obtained in both a fixed Eulerian frame and a frame relative to local coordinates defined in terms of the instantaneous plume edge. In an Eulerian frame we observe that the time-averaged distributions of vertical and horizontal velocity are self-similar, the vertical velocity being well represented by a Gaussian distribution. We condition these measurements on whether fluid is inside or outside of the plume, and whether fluid inside is mixed plume fluid or engulfed ambient fluid. We find that, on average, 5 % of the total vertical volume transport occurs outside the plume and this figure rises to nearly 14 % at heights between large-scale coherent structures. We show that the fluxes of engulfed fluid within the plume envelope are slightly larger than the vertical transport outside the plume – indicating that ambient fluid is engulfed into the plume envelope before being nibbled across the turbulent/non-turbulent interface (TNTI) and then ultimately irreversibly mixed. Our new measurements in the plume coordinate (following the meandering fluctuating plume) show the flow within the plume and in the nearby ambient fluid is strongly influenced by whether an eddy is present locally within the plume, or absent. When an eddy is present and the plume is wide, the vertical velocities near the plume edge are small and hence all vertical transport is inside the plume. In regions where the plume is narrow and there is no eddy, large vertical velocities and hence transport are observed outside the plume suggesting that pressure forces associated with the eddies accelerate ambient fluid which is then engulfed into the plume. Finally, we show that observing significant vertical velocities beyond the scalar edge of the plume does not suggest that the characteristic width of the velocity distribution is greater than that of the scalar field; on the contrary, we show our observations to be consistent with a buoyancy distribution that is up to 20 % wider than that of the velocity. Measurements in the plume coordinates show that the mixing of momentum across the plume results in a distribution for which the differential entropy is close to maximal and the mixing of momentum is uninhibited (i.e. not bounded) by the TNTI of the plume. Furthermore, our measurements suggest that the scalar mixing across the plume may also result in a distribution for which the differential entropy is close to maximal but, in contrast to the momentum, the scalar mixing is strictly bounded by the plume edge.
登录
查看更多内容
同时测量平面湍流射流的湍流/非湍流界面附近的速度和压力
DOI：
--
发表时间：
2016
期刊：
影响因子：
--
作者：
O. Terashima;Y. Sakai;K. Nagata;Yasumasa Ito;Kazuhiro Onishi;Yuichi Shouji
通讯作者：
Yuichi Shouji
DOI：
--
发表时间：
2019
期刊：
影响因子：
--
作者：
Rick Chen
通讯作者：
Rick Chen
影响因子：
8.9
作者：
C. Priestley;F. Ball
通讯作者：
F. Ball
广义非定常羽流理论
影响因子：
3.7
作者：
John Craske;M. van Reeuwijk
通讯作者：
M. van Reeuwijk
影响因子：
3.7
作者：
Dimitrios A. Papantoniou;E. J. List
通讯作者：
E. J. List