表面活性剂溶液中弹性胶束断裂作用下圆柱绕流特征研究  

Study on the flow around a circular cylinder under the elastic micelle scission in surfactant solutions

作　　者：苏晓辉 徐志锋 金辉[2] 王治国[1] 刘佳伦 吴松 SU Xiaohui;XU Zhifeng;JIN Hui;WANG Zhiguo;LIU Jialun;WU Song(College of New Energy,Xi an Shiyou University,710065 Xi’an,China;State Key Laboratory of Multiphase Flow in Power Engineering(SKLMF),Xi an Jiaotong University,710049 Xi’an,China;College of Mechanical Engineering,Xi an Shiyou University,710065 Xi’an,China)

机构地区：[1]西安石油大学新能源学院,西安710065 [2]西安交通大学动力工程及多相流国家重点实验室,西安710049 [3]西安石油大学机械工程学院,西安710065

出　　处：《应用力学学报》2023年第5期1194-1203,共10页Chinese Journal of Applied Mechanics

基　　金：国家自然科学基金资助项目(No.51906202,52074220);陕西省自然科学基金资助项目(No.2019JQ-814);西安石油大学研究生创新与实践能力培养计划项目(No.YCS21213235)。

摘　　要：表面活性剂分子溶于水自组装形成的蠕虫状胶束溶液由于其高表面活性和高黏弹性,具有独特的力学响应特性,呈现出与牛顿流体迥异的流动特征。采用考虑溶液中胶束可逆断裂和重构效应的双组分VCM本构方程,研究了溶液流变学特性,发现溶液拉伸应力随应变率呈现出拉伸硬化-稀化-硬化的强非线性特征。研究了蠕虫状胶束溶液绕圆柱流动的特性,在低雷诺数(Re~0.01)下,当维森贝格数Wi>1时,流场出现较强的不稳定性,绕流尾迹区流场呈现随时间波动的特征,通过功率谱分析发现流场波动具有拟周期特征,当胶束断裂引起流体拉伸应力对弹性响应的非线性增强时,流场波动的不规则性增强。圆柱后缘附近出现一对周期性变化的对称涡,表明流体弹性会促进流动分离的发生,流体拉伸应力对弹性变化的强非线性响应是造成低雷诺数绕流流动不稳定性的根本原因,揭示了蠕虫状胶束溶液在低雷诺数高黏弹性时绕流流动不稳定性的产生机理。Wormlike micellar fluids formed by dissolving surfactants in water have unique mechanical responses due to its high surfactivity and strong viscoelasticity.These properties enable wormlike micellar fluids rich and complicated flow behaviors.By considering the breakage of long chains and the reforming of short chains,a two species VCM model is introduced in this study to numerically investigate the effect of the chain scission on the flow instability.First,the rheological properties are obtained by directly solving the VCM constitutive equation set numerically.The fluid exhibits a strong nonlinear thickening-thinning-thickening phenomenon under the uniaxial tension.The flow passing by a confined cylinder is investigated.The flow becomes significantly unstable at very low Reynolds numbers(Re~0.01)when the Weissenberg number is larger than 1.The fluid velocity in the downstream wake of the cylinder presents a fluctuation with the time.The flow fluctuation is quasi-periodic according to the power spectrum analysis.The flow fluctuation becomes more irregular when the nonlinearity of the variation of the tension stress with the elasticity becomes stronger.A pair of symmetrical vortexes behind the cylinder changing with time are also observed,indicating that the elasticity promotes the flow separation on the cylinder surface.The flow instability is due to the strong nonlinear response of the tension stress within the bulk fluid to the elasticity of the fluid.

关 键 词：表面活性剂 蠕虫状胶束溶液 VCM模型 流动不稳定性 黏弹性流体 

分 类 号：O373[理学—流体力学]