论文标题
由于附近的粒子,施加在振荡板上的过量剪切力
Excess shear force exerted on oscillating plate due to a nearby particle
论文作者
论文摘要
在本文中,我们从理论上研究了在悬挂在板上上方的粘性液体中的刚性粒子的情况下,施加在无限水平面上的剪切力。这项研究在很大程度上是由石英晶体微量平衡(QCM-D)技术激励的,该技术依赖于分析由于在其表面上吸附的小物质而在液体培养基中快速振荡(在MHz范围内)石英晶体盘的响应(复杂阻抗)。实际上,悬浮在振荡晶体附近的液体培养基中的小物质也可能有助于阻抗,因为它们会修饰局部剪切力悬浮液在石英晶体上施加的悬浮力。对于稀释悬浮液,单个颗粒的贡献是加性的,因此,由于位于平面上方任意距离的单个球形粒子,我们的分析仅限于过量的剪切力。考虑了三种不同的情况:(i)限制高固体惯性的情况,而重粒子可以被视为静止; (ii)自由悬浮的任意质量颗粒,经历流体介导的时间周期性旋转和翻译,以及(iii)一个吸附的颗粒,与整个板一起移动而无需旋转。对于小振幅平面振荡,适用不稳定的Stokes流动方程。我们使用反射方法构建这些方程的系列解决方案,而其术语是明确书写的。由于流动从振荡板的指数衰减,仅包含少数低阶项的截断序列显示出与广泛的粒径和分离距离的严格数值结果非常一致的。目前的结果支持这样的观念,即悬浮的小物质对测量的阻抗的流体动力贡献是不可忽略的,甚至是显性的。
In the present paper we theoretically study the shear force exerted on an infinite horizontal plane undergoing fast lateral oscillations in presence of a rigid particle suspended in the viscous liquid above the plate. The study is largely motivated by Quartz Crystal Microbalance (QCM-D) technique which relies on analyzing response (complex impedance) of fast oscillating (in MHz range) quartz crystal disk in the liquid medium due to small substances adsorbed at its surface. In fact, small substances suspended in the liquid medium in the vicinity of the oscillating crystal may also contribute to impedance, as they modify the local shear force the suspending liquid exerts on the quartz crystal. For a dilute suspension the contributions of individual particles are additive and, therefore, our analysis is restricted to the excess shear force due a single spherical particle located at arbitrary distance above the plane. Three distinct cases are considered: (i) limiting case of high solid inertia, whereas the heavy particle can be considered as stationary; (ii) a freely suspended particle of arbitrary mass, undergoing fluid-mediated time-periodic rotation and translation and (iii) an adsorbed particle moving with the plate as a whole without rotation. For small-amplitude plane oscillations the unsteady Stokes flow equations apply. We construct the series solution of these equations using the method of reflections, whereas its terms are written explicitly. Due to the exponential decay of the flow away from the oscillating plate, the truncated series containing only few low-order terms shows an excellent agreement with the rigorous numerical results for a wide range of particle sizes and separation distances. The present results support the notion that the hydrodynamic contribution of the suspended small substances to the measured impedance is non-negligible or even dominant.