Forrester Derek Michael, Huang Jinrui, Pinfield Valerie J
Loughborough University, Chemical Engineering, Loughborough, LE11 3TU, United Kingdom.
Qinetiq Group plc., Cody Technology Park, Ively Road, Farnborough, Hampshire, GU14 0LX, United Kingdom.
Sci Rep. 2019 Mar 20;9(1):4956. doi: 10.1038/s41598-019-40665-9.
Upon application of ultrasonic waves to a suspension of solid particles in liquid, multiple scattering occurs at the particle/liquid interfaces leading to attenuation. It was recently shown through experimental verification that multiple scattering theory must include shear wave influences at the boundary between the liquid and solid particles in a nanofluid when the concentration of the scatterers is even as low as a few percent by volume. Herein, we consider silica spheres of 50-450 nm diameter in the long-wavelength regime to elucidate the form of the shear decay fields at the liquid/solid interface for individual particles. This is important because the overlap of these fields ultimately leads to the conversion of a compressional wave to shear waves and back into the compressional wave, the effect originating due to the density contrast between the particle and the liquid. Therefore, we examine in detail the velocity, vorticity and viscous dissipation in the shear wave field and around the silica spheres using finite element modelling, giving clarity to the viscous boundary effects. We also compare the numerical modelling to semi-analytical results.
当对液体中固体颗粒的悬浮液施加超声波时，在颗粒/液体界面会发生多次散射，从而导致衰减。最近通过实验验证表明，当散射体的浓度低至体积的百分之几时，多次散射理论必须包括纳米流体中液体与固体颗粒边界处的剪切波影响。在此，我们考虑长波长范围内直径为50 - 450 nm的二氧化硅球体，以阐明单个颗粒在液/固界面处的剪切衰减场形式。这很重要，因为这些场的重叠最终会导致压缩波转换为剪切波，然后再转换回压缩波，这种效应是由于颗粒与液体之间的密度差异引起的。因此，我们使用有限元建模详细研究了剪切波场中以及二氧化硅球体周围的速度、涡度和粘性耗散，明确了粘性边界效应。我们还将数值建模与半解析结果进行了比较。
