Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
Int J Mol Sci. 2021 Jul 15;22(14):7573. doi: 10.3390/ijms22147573.
The phenomenon of drag reduction (known as the "Toms effect") has many industrial and engineering applications, but a definitive molecular-level theory has not yet been constructed. This is due both to the multiscale nature of complex fluids and to the difficulty of directly observing self-assembled structures in nonequilibrium states. On the basis of a large-scale coarse-grained molecular simulation that we conducted, we propose a possible mechanism of turbulence suppression in surfactant aqueous solution. We demonstrate that maintaining sufficiently large micellar structures and a homogeneous radial distribution of surfactant molecules is necessary to obtain the drag-reduction effect. This is the first molecular-simulation evidence that a micellar structure is responsible for drag reduction in pipe flow, and should help in understanding the mechanisms underlying drag reduction by surfactant molecules under nonequilibrium conditions.
减阻现象（即“托姆效应”）在许多工业和工程应用中都有体现，但目前还没有构建出明确的分子层面理论。这既是由于复杂流体的多尺度性质，也是由于难以直接观察非平衡状态下的自组装结构。基于我们进行的大规模粗粒化分子模拟，我们提出了在表面活性剂水溶液中抑制湍流的可能机制。我们证明，保持足够大的胶束结构和表面活性剂分子的均匀径向分布对于获得减阻效果是必要的。这是首次从分子模拟的角度证明胶束结构是管流减阻的原因，这应该有助于理解非平衡条件下表面活性剂分子减阻的机制。
