Research Projects

Dynamics of gas-solid and liquid-solid suspensions

In our group, we use direct numerical simulations to study flow and transport in flowing suspensions to extract information for the development of closure relations and to improve understanding of the physics in these complex systems. The problems that are being studied currently include: 1) Dynamics of binary and polydisperse suspensions; 2) Homogeneous cooling of a gas-solid particulate system in the absence of gravity; and 3) Enhanced heat and mass transfer in sheared suspensions.

Figure 1: Left panel is a binary suspension containing 1727 small particles and 27 large particles. The size of the smaller particles is 1/4 of that of the larger ones. Each type of particles occupies 10% of the total volume. RIGHT panel shows the pressure-driven Stokes flow through the binary particle assembly (flow direction from left to right). The fluid velocity component in the direction of the pressure gradient is plotted on two slices cutting through the simulation domain. Only particles intersecting with the two slices are shown.

A couple of videos are provided below.

Video 1. Density segregation of light and heavy particles in a cell filled with liquid. The Reynolds numbers of the particles are small, and column instability occurs due to chaotic hydrodynamic interactions. The densities of the particles relative to the fluid are 0.6 and 1.4. The volume fractions are 15% and 15%. There are 2590 particles in this simulation. Click link to download movie (54MB)

Video 2. Homogeneous cooling of a gas-solid suspension. The initial velocity fluctuation measured in terms of a Reynolds number is 30. Particles are 1000 times denser than the interstitial gas. The particle volume fraction is 30% and the sizes are shrunk to facilitate visualization. The homogeneous cooling process, as viewed from this video, is clearly unstable with formation of clusters and streamers. From such simulations, one can assess the relative importance of viscous drag and dissipative collisions in cluster formation in gas-solid flows. Click link to download movie (19MB)

Video 3. Simulation of Brownian tracer motion in a sheared suspension containing a single neutrally buoyant particle. The tracers are able penetrate the surface of the particle, and can be used to simulate heat transfer processes. Click link to download movie (2MB)

Simulation of single- and two-phase flows in 2D/3D synthetic porous media

Stochastic two- and three-dimensional porous media geometry models made by randomly oriented channels, fractures, or fibers are used to study flow, transport, and reaction in nanoporous materials where the geometry of the pores cannot be obtained easily via conventional X-ray tomography techniques. Fluid flow in these geometries are solved using single- and multiphase lattice Boltzmann solvers. Currently, we are funded by RPSEA (www.rpsea.org) to develop a simulator to study formation damage in unconventional gas reservoirs (shale and tight gas) that feature nano-sized pores. The project will last for three years (2010-2013), and involve collaborations from Missouri University of Science and Technology and Chemical Engineering Department, Colorado School of Mines.


Figure 2. Computer-generated model of a homogeneous (left) porous medium made by inter-connected microchannels and a highly heterogeneous (right) porous medium consisting of vugs and inter-vug connections.