Dynamics of nanoparticles and bubbles in creeping flows of viscous fluids

Dynamics of nanoparticles and bubbles in creeping flows of viscous fluids

This research deals with the study of dynamics of nanoparticles and bubbles in creeping flows of viscous fluids. The study was based on theoretical approaches and numerical methods. To conduct numerical simulations, the original FORTRAN codes were developed and realised on a desktop computer. To process the obtained results the Mathcad software was actively used.

Firstly, the dynamics of two unlike and like charged particles in viscous fluid in the creeping flow approximation was studied. Two types and different models of viscous drag forces were taken into consideration. The particles’ trajectories under the influence of all these forces were studied and compared with those immersed in inviscid fluid.

Next, the complex dynamics of small rigid particles under the influence of acoustic radiation force were considered. Our analysis was based on a more advanced model in comparison with those used in the earlier works (Sarvazyan & Ostrovsky, 2009; Ostrovsky, 2015). In addition to the Stokes drag force, the model used in this study included particle inertia, added mass effect, and the Boussinesq–Basset drag force, the effects of these were ignored in the cited papers. It has been shown through numerical solutions that all of these additional effects can be important at some stages of particle motion, whereas in other stages they can be neglected. The particle motion was considered both for the plane and cylindrical geometries. An interesting and prospective method of particle control in a fluid was studied by periodic switching of the acoustic modes in a resonator.

In the last Chapter there is an analysis of the influence of memory integral drag forces on the resonance characteristics of oscillating solid particles and gaseous bubbles in a viscous fluid under the influence of an external sinusoidal force. It has been shown that the memory integral drag forces lead to the widening of resonance curves and the reduction of resonance peaks, so that the effective quality of oscillator significantly decreases in comparison with the similar oscillator with only Stokes drag force.