Direct numerical simulation of a hydrodynamic interaction between settling particles and rising microbubbles

• A single multiphase DNS framework for particle–bubble interactions in a liquid.
• Simultaneous handling of both deformable and non-deformable objects in a fluid.
• Validated against a series of well-established results from the literature.
• Influence on attachment from initial separation, particle density & bubble shape.

We present in this paper a framework for Direct Numerical Simulation (DNS) of flows involving non-deformable (solid particles and spherical bubbles) and deformable (bubbles and droplets) moving objects suspended in a fluid (liquid or gas). The simulation framework is based on solving a shared set of momentum equations for the phases involved. Special care is taken to adapt the method for simulating solid particles in a flow. We first validate the framework with a series of well-established results from the literature. Then, we demonstrate its capabilities by investigating the influence of relevant parameters (e.g. the shape of the bubble, particle density and the separation distance) on the behaviour and the interaction of deformable and non-deformable objects in the flow. The suggested framework successfully reproduces both the particle–bubble attachment when the initial horizontal distance between their centres is small, and that the particle passes the bubble without attaching when this distance is large. Furthermore, we show that the probability of a successful attachment decreases if the bubble Eötvös and Morton numbers are substantially larger than unity. Finally, we demonstrate the capability of the proposed method to handle flow situations that involve a simultaneous presence of both multiple solid particles and multiple deformable objects.

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