Stability analysis of solid particle motion in rotational flows

Paradisi, P. and Tampieri, F. (2001) Stability analysis of solid particle motion in rotational flows. Il nuovo cimento C, 24 C (3). pp. 407-420. ISSN 1826-9885

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A two-dimensional model of a rotational flow field is used to perform the stability analysis of solid particle motion. It results that the stagnation points are equilibrium points for the motion of particles and the stability analysis allows to estimate their role in the general features of particle motion and to identify different regimes of motion. Furthermore, the effects of Basset history force on the motion of particles lighter than the fluid (bubbles) are evaluated by means of a comparison with the analytical results found in the case of Stokes drag. Specifically, in the case of bubbles, the vortex centres are stable (attractive) points, so the motion is dominated by the stability properties of these points. A typical convergence time scale towards the vortex centre is defined and studied as a function of the Stokes number St and the density ratio γ. The convergence time scale shows a minimum (nearly, in the range 0.1 < St < 1), in the case either with or without the Basset term. In the considered range of parameters, the Basset force modifies the convergence time scale without altering the qualitative features of the particle trajectory. In particular, a systematic shift of the minimum convergence time scale toward the inviscid region is noted. For particles denser than the fluid, there are no stable points. In this case, the stability analysis is extended to the vortex vertices. It results that the qualitative features of motion depend on the stability of both the centres and the vertices of the vortices. In particular, the different regimes of motion (diffusive or ballistic) are related to the stability properties of the vortex vertices. The criterion found in this way is in agreement with the results of previous authors (see, e.g., Wang et al. (Phys. Fluids, 4 (1992) 1789)).

Item Type: Article
Uncontrolled Keywords: Particles and aerosols ; Multiphase and particle-laden flows ; Drops and bubbles
Subjects: 500 Scienze naturali e Matematica > 550 Scienze della Terra > 551 Geologia, Idrologia, Meteorologia
Depositing User: Marina Spanti
Date Deposited: 10 Mar 2020 18:37
Last Modified: 10 Mar 2020 18:37

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