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Influence of length of polymer aggregation on turbulent friction drag reduction effect

机译：聚合物聚集体长度对湍流减阻效果的影响

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The influence of the length of polymer aggregation on the turbulent drag reduction effect is investigated through numerical simulation. Polymer aggregation is modeled using a bead-spring chain model, which is a discrete element model. Simulations are carried out for different total natural lengths of the model at a friction Reynolds number of 180, and the numerical results for different spring constants by Fujimura et al. (2016) are analyzed. In addition, the time scale of the model, which corresponds to relaxation time, is investigated using oscillating Couette flow. Relaxation time increases as the total natural length increases and the spring constant decreases, and the drag reduction rate in turbulent channel flow increases with relaxation time. In the present study, it is determined that relaxation time is correlated with the length of the elongated model in turbulent channel flow. The relation between the drag reduction rate and the length of the elongated model can be expressed by a logarithmic function. According to the relational expression, it is expected that the drag reduction effect occurs when the length of the elongated model is longer than the diameter of vortical structures. In the visualization of turbulent flow field, it can be observed that longer models exhibit strong energy dissipation through interaction with the fluid, and suppress velocity fluctuations.
机译：通过数值模拟研究了聚合物聚集体长度对湍流减阻效果的影响。使用珠-弹簧链模型（一个离散元素模型）对聚合物聚集进行建模。在摩擦雷诺数为180的情况下，对模型的不同总自然长度进行了仿真，Fujimura等人针对不同的弹簧常数进行了数值计算。 （2016）进行了分析。此外，使用振荡库埃特流研究与松弛时间相对应的模型时间尺度。随着自然总长度的增加和弹簧常数的减小，松弛时间增加，并且湍流通道流动中的减阻率随松弛时间的增加而增加。在本研究中，确定了湍流通道流动中的弛豫时间与细长模型的长度相关。减阻速率与拉长模型的长度之间的关系可以通过对数函数表示。根据该关系式，预计当拉长模型的长度比旋涡结构的直径长时，会产生减阻效果。在湍流场的可视化中，可以观察到更长的模型通过与流体的相互作用展现出强大的能量耗散，并抑制了速度波动。

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