In this paper, a systematic numerical study of the local resistance coefficients of vertical L-shaped and Z-shaped pipes for gas‒liquid two-phase flows under vertical conditions was carried out using a realizable k-ε turbulence model combined with a mixture model in Fluent software. Specifically, the influence of the Reynolds number Re_l, the gas-phase volume rate α, the radius–diameter ratio R/D, the height–diameter ratio H/D, and the two-phase flow direction on the local resistance coefficient ξ were discussed in detail. ξ of the vertical Z-shaped pipe decreases with increasing Re_l, while ξ of the vertical L-shaped pipe does not change significantly. In a specific range, ξ of vertical L-shaped and Z-shaped pipes increases with increasing α and decreases with increasing R/D. In Z-shaped pipes, under the upward flow condition, ξ increases with increasing H/D, and under the downward flow and horizontal flow conditions, ξ first decreases and then increases with increasing H/D. Overall, upward and downward flow conditions have a larger ξ than the horizontal flow condition. When H/D is larger than 14, ξ tends to be stable under all three flow conditions. Finally, the relationship equations between ξ and Re_l, α, R/D, and H/D were fitted, which agreed with the numerical results.

中文翻译：

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垂直L型和Z型管道中气液两相流的局部阻力

在本文中，使用可实现的k-ε湍流模型结合混合模型，对垂直 L 形和 Z 形管道在垂直条件下气液两相流的局部阻力系数进行了系统的数值研究在 Fluent 软件中。具体地，雷诺数Re _l、气相体积率α、径径比R/D、高径比H/D、两相流向对局部阻力系数ξ的影响进行了详细讨论。竖直 Z 形管的 ξ 随 Re l 的增加而减小_，而ξ垂直 L 形管道的变化不大。在一定范围内，立式L型和Z型管的ξ随α的增大而增大，随R/D的增大而减小。在Z形管道中，在向上流动条件下，ξ随H/D的增大而增大；在向下流动和水平流动条件下，ξ随H/D的增大先减小后增大。总体而言，向上和向下流动条件的ξ比水平流动条件大。当H/D大于 14 时，ξ在所有三种流动条件下趋于稳定。最后，拟合了ξ与Re _l、α、R/D和H/D之间的关系方程，与数值结果一致。