Direct Numerical Simulations of Particle-laden Flows

Laminar and turbulent flows containing fixed and moving discrete entities (solid particles, droplets, or microbubbles) are relevant to many environmental and natural processes. In cloud microphysics, the growth of cloud droplets by turbulent collision-coalescence is crucial to warm rain initiation. In air-sea interaction, the production and transport of droplets and bubbles affect the energy and mass exchanges between the atmosphere and the ocean. In soil porous medium, the transport and deposition of colloids influence contaminant redistribution.
Since experimental measurements of these flows at micro scales prove to be extremely difficult, direct numerical simulation is playing an increasingly important role both in advancing our understanding and in providing a quantitative prediction of the multiscale particle-fluid and particle-particle interactions. In the last 10 years, several efficient methods and algorithms have been developed to treat particle-laden flows, with increasing spatial resolution and better micro-scale physicl representation.
In this talk, I will first present and overview of some available numerical methods and contrast their advantages and drawbacks. Several examples will be discussed where direct simulations have led to important original discoveries in particle-laden flows. Finally, I will illustrate on-going activities and challenging computational issues in direct simulations of turbulent particle-laden flows.