表面活性剂紊流输水减阻的雷诺应力及能量传递

Characteristics of Turbulent Reynolds Stress and Energy-Transporting in a Surfactant Aqueous Solution Drag-Reducing Flow

为揭示表面活性剂减阻水溶液紊流的减阻机理,通过分析各种试验结果后指出,雷诺剪切应力的大幅降低是源于表面活性剂的去相关作用;通过二维矩形封闭流道的时均能量、紊流能量的平衡分析,表明胶束剪切应力从时均流获得能量对低雷诺应力工况下紊流的产生和维持起了决定性作用,减阻率与胶束剪切应力从时均流获得的能量大小之间存在负相关关系。在二维明槽中,使用二维激光多普勒流速仪实测的表面活性剂减阻水溶液的主流方向速度脉动能谱表明,大尺度涡体含能较牛顿流体大,小尺度涡体含能低于牛顿流体,能量耗散尺度增大,这是表面活性剂减阻水溶液紊流能量传递的基本特征。

In order to clarify the drag-reducing mechanism of turbulent through adding surface active agent to pure water,after examining previous investigations,it is indicated that the substantial decrease of Reynolds shear stress is due to the effects of decorrelation caused by adding surfactant.From a balance analysis on time-average energy and turbulent energy in an enclosed two-dimensional rectangle flume flow with weak Reynolds shear stress,added micelle shear stress plays a key role in the forming and maintaining the turbulent flow for drag-reducing surfactant solution.Furthermore,the bigger the micelle fluctuating energy taken from total mean flow,the smaller the drag reduction rates are.For the two dimensional open flume,through analyzing the turbulent energy spectrum of drag-reducing surfactant solution measured by a two dimensional laser Doppler current-meter,large scale vortices contain more energy than that of Newtonian fluid.Conversely,small vortices contain less energy,and the scale of energy dissipation is increased.This is the basic characteristics of the energy transporting in a surfactant solution drag-reducing flow.