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Fluid Dynamics (FD)

   

Direct Numerical Simulations of Breakup and Collision of Liquid Particles

Direct Numerical Simulations of Breakup and Collision of Liquid Particles

Droplets and bubbles are one of common and beautiful phenomena of our daily life, however, the physics behind are very interesting and complicated. Researcher and scientists have worked on this subject for decades; however the understanding of the underlying physics is still limited.

Here, a moving mesh interface tracking (MMIT) method is employed to simulated two-phase flows, such as droplet breakup and merging, in order to shed some light on the understanding of the physics. In this method, the interface is zero-thickness and moves with the fluids. Thus, there is no smearing of the fluid properties and the mass of each phase is conserved naturally. The challenge for this method is to maintain good mesh quality as the moving mesh eventually leads to worsen of the mesh quality and to handle topological changes. Mesh adaptations including mesh smooth, edge swapping, and edge collapsing and bisection are applied locally to achieve good mesh quality and also to obtain computing efficiency. Mesh combination and mesh separation are employed to deal with liquid particle breakup and merging respectively.

Numerical simulations of the relaxation and pinch-off an initially elongated droplet in another viscous fluid show the capabilities of the method: (a). capturing small length scale (see Figure1); (b) predicting the right physics (Figure 2); (c) unveiling the underlying physics.

meshes of the liquid particle before breakup with blow-up view on the right.

Neck shape. Stream lines before breakup

Equal-sized droplet-pair collisions including head-on and off-center are simulated.

Head on collision

Off-center coalescence

Meshes of head-on just after initial contact.

 

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This page is last updated at: 30-NOV-2010