A Study on the Mechanism of Turbulence Controllability Caused by the Rod-like Micelles of Surfactants

在湍流管流中加入少量的阳离子表面活性剂和适当的反离子，可显著降低阻力。表面活性剂的减阻实验表明，即使在大管径的情况下，也能获得较大的减阻量。表面活性剂溶液在较高剪切速率下的流变性是减阻流动中湍流控制的关键。剪切诱导态，在本报告中简称为SIS，被认为是在剪切场作用下形成的棒状胶束的聚集态。SIS可能会导致表面活性剂形成非常大的团聚结构。SIS是在足够高的剪切速率条件下建立的，剪切速率在剪切速率的固定时间导数上线性降低。利用Maxwell模型的松弛函数模拟了在这样的剪切历史下观测到的剪应力响应。从实验结果可以得到很大的驰豫时间。松弛的蒂姆·…更多的e与切变率的时间导数相关。该弛豫时间被用来预测表面活性剂在管流中的减阻效果。粘弹性阻尼因子模型是由Usui等人提出的。被用作湍流模型。在SIS下实验测定的剪切粘度也被用于该湍流模型。利用该模型成功地预测了不同管径下的减阻效果。由此得出结论：考虑松弛时间和剪切粘度的粘弹性减阻因子模型可以定量预测SIS条件下管道的减阻效果。对于直径为1000 mm的管子，减阻效果可达80%以上。得出的重要结论是，表面活性剂减阻适用于全尺寸的区域供热和供冷系统。本研究的最终目的是为了了解湍流减阻现象的机理，完全理解这一现象的机理是非常困难的，以往也没有人能够成功。对减阻机理的理解还需在今后的研究中继续进行。较少

The addition of small amount of a cationic surfactant with suitable counter ion causes a drastic drag reduction in a turbulent pipe flow. The surfactant drag reduction experiments show that the large amount of drag reduction even in a large pipe diameter is obtained. The theological characteristics of surfactant solutions under considerably high shear rate is the key function for the turbulence control in a drag-reducing flow. Shear induced state, abbreviated in this report as SIS, is believed as a agglomerated state of rod-like micelles aliened by a shear field. SIS may cause a very large agglomerate structure of surfactants. The SIS was established at sufficiently high shear rate condition, and the shear rate was decreased linearly at fixed time derivative of shear rate. The shear stress response observed under such a shear history was simulated by using the relaxation function of Maxwell model. Very large relaxation time was obtained from the experimental results. The relaxation tim … More e was correlated by the time derivative of shear rate. This relaxation time was used to predict the surfactant drag reduction in pipe flow. The viscoelastic damping factor model previously proposed by Usui et al. was employed as a turbulence model. The shear viscosity experimentally determined under SIS was also used for this turbulence model. The drag reduction for different pipe diameter was successfully predicted by this model. Thus, it was finally concluded that drag reduction was quantitatively predictable by using the viscoelastic damping factor model with relaxation time and shear viscosity under SIS.The above mentioned turbulence model was applied for the prediction of drag reduction in large scale pipeline systems. More than 80% drag reduction effectiveness was predicted for 1,000 mm pipe diameter case. The important conclusion is that the surfactant drag reduction is applicable to the full scale district heating and cooling systems. and the drag reduction effectiveness is predictable by the model proposed in this study.This study was finally aimed to understand the mechanism of turbulent drag-reducing phenomenon The complete understanding of the mechanism is very difficult, and no one has succeeded in the past. The effort to understand the drag reduction mechanism must be continued in the future study. Less