Momentum and energy transfer in open-channel flow over streamwise ridges
Momentum and energy transfer in open-channel flow over streamwise ridges
复制标题
流向山脊明渠流中的动量和能量传递
DOI：
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发表时间：
2021
影响因子：
3.7
通讯作者：
V. Nikora
中科院分区：
文献类型：
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作者：
A. Zampiron;S. Cameron;V. Nikora
摘要利用三维粒子图像测速技术对流向三角形脊上的明渠水流进行了测量，研究了脊诱导的二次流与湍流之间的相互作用。针对0.4至4.0流动深度（$H$）之间的山脊间距（$s$）范围，分析了双平均（空间和时间）动量和能量守恒方程中的项。双平均方程巧妙地分割动量和能量通量到湍流和SC的贡献，使他们非常适合这项研究。所获得的数据表明，在0.4和2.0之间的$s/H$的范围内，由于SC的归一化动量和能量通量近似崩溃时，绘制为$（z-d）/s$的函数，其中$z$是垂直坐标和$d$一个常数，对齐SC细胞中心的海拔。的SC控制的形状的平均速度分布的垂直梯度的双平均流向速度发现成反比的SC细胞中心附近的海拔$S$。将总动能划分为双平均（DMKE），分散（DKE）和湍流（SATKE）分量，并考虑每个分量的平衡方程表明，在SC细胞中心的高度，通过与DMKE交换的SATKE的生产率在幅度上与通过与DKE交换的生产率（由于SC）相当。对于所有的脊间距，SATKE减少相比，一个没有脊基准的情况下，由于抑制非常大规模的湍流运动的SC。最后，它表明，能量提供给SC的湍流。
Abstract Stereoscopic particle image velocimetry measurements of open-channel flows over streamwise-orientated triangular-shaped ridges were used to explore interactions between ridge-induced secondary currents (SCs) and turbulence. Terms in the double-averaged (in space and in time) momentum and energy conservation equations were analysed for a range of ridge spacings ($s$) between 0.4 and 4.0 flow depths ($H$). The double-averaged equations neatly partition momentum and energy fluxes into turbulence and SC contributions, making them well suited to this study. The obtained data indicate that for a range of $s/H$ between 0.4 and 2.0, the normalised momentum and energy fluxes due to SCs approximately collapse when plotted as functions of $(z-d)/s$, where $z$ is the vertical coordinate and $d$ a constant that aligns the elevations of SC cell centres. The SCs controlled the shape of the mean velocity distribution with the vertical gradient of the double-averaged streamwise velocity found to be inversely proportional to $s$ near the elevations of SC cell centres. Partitioning the total kinetic energy into double-mean (DMKE), dispersive (DKE) and turbulent (SATKE) components and considering the balance equation for each component indicated that at the elevation of SC cell centres the production rate of SATKE via exchange with DMKE was comparable in magnitude to the production rate via exchange with DKE (due to SCs). For all ridge spacings, SATKE was reduced compared to a no-ridge benchmark case due to suppression of very-large-scale turbulent motions by the SCs. Finally, it is demonstrated that energy is supplied to SCs by turbulence.