Du Di, Hilou Elaa, Biswal Sibani Lisa
Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, USA.
Phys Rev E. 2016 Jun;93(6):062603. doi: 10.1103/PhysRevE.93.062603. Epub 2016 Jun 10.
The dynamics of magnetorheological fluids have typically been described by the Mason number, a governing parameter defined as the ratio between viscous and magnetic forces in the fluid. For most experimental suspensions of magnetic particles, surface forces, such as steric and electrostatic interactions, can significantly influence the dynamics. Here we propose a theory of a modified Mason number that accounts for surface forces and show that this modified Mason number is a function of interparticle distance. We demonstrate that this modified Mason number is accurate in describing the dynamics of a rotating pair of paramagnetic colloids of identical or mismatched sizes in either high or low salt solutions. The modified Mason number is confirmed to be pseudoconstant for particle pairs and particle chains undergoing a stable-metastable transition during rotation. The interparticle distance term can be calculated using theory or can be measured experimentally. This modified Mason number is more applicable to magnetorheological systems where surface forces are not negligible.
磁流变液的动力学特性通常由梅森数来描述，梅森数是一个控制参数，定义为流体中粘性力与磁力之比。对于大多数磁性颗粒的实验悬浮液，表面力，如空间位阻和静电相互作用，会显著影响动力学特性。在此，我们提出了一种考虑表面力的修正梅森数理论，并表明这种修正梅森数是粒子间距离的函数。我们证明，这种修正梅森数能够准确描述在高盐或低盐溶液中，一对大小相同或不同的顺磁性胶体旋转时的动力学特性。对于在旋转过程中经历稳定-亚稳转变的粒子对和粒子链，修正梅森数被证实为伪常数。粒子间距离项可以通过理论计算，也可以通过实验测量。这种修正梅森数更适用于表面力不可忽略的磁流变系统。
