BiconeDrag updated – A data processing application for the oscillating conical bob interfacial shear rheometer

We present a new improved version of BiconeDrag, a code that allows one to obtain the values of interfacial dynamic moduli from dynamic experiments performed in rotational interfacial shear rheometers with bicone probes. The general structure of the program remains the same: starting from the values of the torque/angular displacement amplitude ratio, and by using the equations of the hydrodynamic field, it is possible to decouple the contribution of the subphase (bulk) drag from the true interfacial drag. In this new version we have improved the implementation of the boundary condition at the interface so that now it is built as second order centered finite differences (SOCFD hereafter) with the help of a line of phantom nodes. The new numerical implementation of the interfacial boundary condition yields smoother velocity profiles at the bicone rim, which result in a more accurate separation of interfacial and subphase drags and, consequently, in a more precise calculation of the interfacial dynamic moduli.

本研究提出了BiconeDrag的改进新版本，该代码可通过搭载双锥探头（bicone probes）的旋转界面剪切流变仪（rotational interfacial shear rheometers）开展的动态实验，获取界面动态模量（interfacial dynamic moduli）的数值。该程序的整体结构保持不变：以扭矩与角位移幅值比的数值为基础，结合流体力场方程，可将亚相（subphase，即体相）拖曳的贡献与真实界面拖曳分离开来。在本次更新的版本中，研究人员优化了界面边界条件的实现方式：借助一系列虚节点（phantom nodes），将边界条件构建为二阶中心有限差分（second order centered finite differences，下文简称SOCFD）。新型界面边界条件的数值实现方案，使双锥边缘处的速度分布更为平滑，由此可更精准地分离界面拖曳与亚相拖曳，进而更精确地计算得到界面动态模量。