减阻用表面活性剂溶液分子动力学模拟研究进展

减阻用表面活性剂在能源动力及化工领域有着广泛应用,在管道流体中加入少量表面活性剂可以使流动阻力大大降低从而节约能源,对于表面活性剂减阻机理的讨论也是近些年学者关注的热点之一.本文不仅对课题组前些年在表面活性剂溶液流变性、湍流减阻、减阻与传热的相关性、布朗动力学模拟方面的工作进行了概述,而且详细介绍了近三年来在表面活性剂粗粒化分子动力学模拟方面的研究成果.粗粒化模拟是近年来发展起来的方法,目前已广泛应用于化学、生物等诸多领域.在粗粒化分子动力学模拟方面的工作包括:表面活性剂溶液的流变性能与微观结构、表面活性剂溶液湍流减阻机理研究、湍流减阻失效分析三个部分.通过对表面活性剂溶液分子动力学模拟研究进展的回顾,作者认为,利用粗粒化分子动力学模拟方法可以合理揭示表面活性剂胶束的结构与流变性的对应关系,对胶束的断裂与再连接能力进行多维度的评价,如胶束的拉伸能、断裂能、最大拉伸长度、结合能、$\zeta$电势、疏水基驱动作用等方面.并对"黏弹说"减阻机理进行分子模拟层面的验证,对实际应用中的湍流减阻失效原理进行初步分析.最后,根据对近几年分子动力学模拟工作的总结,展望了未来粗粒化分子动力学模拟在表面活性剂方面的研究方向. 

PROGRESS IN MOLECULAR DYNAMICS SIMULATIONS OF SURFACTANT SOLUTION FOR TURBULENT DRAG REDUCTION 1)

Surfactant additives for turbulent drag reduction have been widely used in energy power and chemical industry. The addition of a small amount of surfactant additives in the pipeline fluid can greatly reduce the flow friction resistance and save energy. In recent years, the research on the mechanism of surfactant drag reduction is also a hot scientific topic. This paper not only summarized our work on the rheology of surfactant solution, surfactant drag reduction, the correlation with surfactant drag reduction and heat transfer, Brownian dynamics simulations in the latest years, but also concerning some works based on the coarse grained molecular dynamics (CGMD) simulations in the past three years, which will be elaborated in detail. The CGMD simulation is developed these years and now widely used in chemistry, biology and many other aspects. Our CGMD simulation work includes three parts, which are the rheology properties and its microstructures of the surfactant solution, the mechanism of turbulent drag reduction by surfactant additives, the analysis of turbulent drag reduction failure phenomenon on the pipeline transportation system. Through reviewing the progress in our CGMD simulation work, we believe that the CGMD simulation method can reasonably explain the rheological behavior of surfactant solutions, and the relationship between the rheology and the surfactant micelle structure can be well studied by using the coarse grained model. The breakage and the recombination behaviors of surfactant micelles can be evaluated from a multidimensional system including the extensional energy, the breakage energy, the maximum reasonable stretching distance, coalescence energy, zeta potential, or hydrophobic driving effect. Besides, the "viscoelasticity theory" can be proved from a molecular scale. Last but not least, the mechanism of turbulent drag reduction failure phenomenon can also be analyzed by CGMD simulation by simulating different failure reasons. At last, we summarize the CGMD simulation work on surfactant in recent years and then the direction of the future work about CGMD simulation work on surfactant is predicted.