Helical pipes have been widely applied in a vast range of industries owing to the remarkable characteristics. In practice they still face the challenge of undesirable increased pressure resistance. The investigation on the flow characteristics in helix is essential to explore the pressure loss mechanism. In this paper the k-omega model and k-omega SST model are utilized to investigate the flow characteristics in helical pipes with varying Reynolds number and geometry parameters including coil radius, pipe diameter and coil pitch. The influence of each variable on the flow field, especially axial and secondary velocity distribution, is thoroughly examined. The relationship between Darcy friction factor and different dimensionless variables is analyzed, which turns out to be positively dependent on radius ratio and inversely dependent on Reynolds number. The available correlations of friction factor in the laminar and turbulent regime in literature are presented and the prevailing forms are summarized, some in good accordance with simulation. Based on the results, new correlations are proposed and the coefficients are determined by virtue of nonlinear data fitting, which could provide assistance for the design and optimization of helical pipes.

中文翻译：

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螺旋管单相流动特性及摩擦压降数值研究

螺旋管以其显着的特性被广泛应用于各行各业。在实践中，他们仍然面临着不希望的增加的耐压性的挑战。研究螺旋中的流动特性对于探索压力损失机制至关重要。在本文中，k-omega 模型和 k-omega SST 模型用于研究具有不同雷诺数和几何参数（包括盘管半径、管道直径和盘管节距）的螺旋管中的流动特性。每个变量对流场的影响，尤其是轴向和二次速度分布，都经过彻底检查。分析达西摩擦系数与不同无量纲变量的关系，事实证明，这与半径比正相关，而与雷诺数呈负相关。文献中介绍了层流和湍流状态下摩擦系数的可用相关性，并总结了主要形式，其中一些与模拟非常吻合。在此基础上，提出了新的相关性，并通过非线性数据拟合确定了系数，可为螺旋管的设计和优化提供帮助。