Particle-laden turbulent flow is a complex problem that plays an important role in a variety of industrial and environmental applications, including pneumatic mixing, thermal processes in manufacturing, heat transfer in power stations, and sea spray in hurricanes. Due to the fundamental importance and practical interests of these problems, turbulent particle-laden flows have received considerable attention in experimental and numerical studies in recent years. Under the influence of turbulence, particles exhibit a variety of phenomena, such as dispersion, concentration, deposition, and resuspension. On the other hand, due to the interactions between turbulence structure and dispersed particles, turbulence characteristics of momentum and heat transport can be modified by the presence of particles.
Our group has been performing research on the momentum and heat transfer in particle-laden turbulent channel flows. We are also investigating the role sea sprays play in air-sea interactions. We have developed a coupled level-set and volume-of-fluid method to simulate the air and water flows in wave breaking. A Lagrangian particle tracking method based on a point-force approximation is used to simulate the motions of sea spray. We have simulated spray generation and transport in wind over breaking wave.
In addition to point particle simulation, we also focus on fully resolved particle simulation. In this simulation, flow field is resolved by direct numerical simulation while the particle motion is calculated by the Newton-Euler equations, with the particle-turbulence interaction solved using the immersed boundary method. Particle resolved simulation can provide us deep insights into particle-turbulence interaction physics to help improve the point particle model.
We have performed particle resolved simulation to study turbulence modulation by sediment transport. In this study, the discrete element method is used to resolve particle-particle and particle-wall collisions. The statistical properties and structure of turbulence can be modified by the particles. We are currently investigating the mechanisms by which particles influence turbulence properties and structures.
Another topic on particle-laden flows we are interested in is particle clustering. The tendency of particles to aggregate while interacting with fluid flows, termed clustering, is seen in numerous situations like atmospheric clouds and swimming microorganisms. One way to identify particle clusters is through the Voronoi diagram, and based on the identification method at one time instant, we have introduced a new methodology to track clusters across successive realizations of the flow and performed studies on inertial particles in homogenous isotropic turbulence (HIT). This study has provided physical insights into clusters' birth and death, and illustrated that relatively quiescent state of flow is a necessary condition for a cluster's survival.
Liu, Y., Shen, L., Zamansky, R. & Coletti, F. (2020), “Life and death of inertial particle clusters in turbulence,” Journal of Fluid Mechanics, Vol. 902, R1.
Pan, M., Liu, C., Li, Q., Tang, S., Shen, L. & Dong, Y. (2019), “Impact of spray droplets on momentum and heat transport in a turbulent marine atmospheric boundary layer,” Theoretical and Applied Mechanics Letters, Vol. 9, pp.71-78.
Liu, C., Tang, S., Dong, Y. & Shen, L. (2018), “Heat transfer modulation by inertial particles in particle-laden turbulent channel flow,” Journal of Heat Transfer, Vol. 140, 112003.
Tang, S., Yang, Z., Liu, C., Dong, Y. & Shen, L. (2017), “Numerical study on the generation and transport of spume droplets in wind over breaking waves,” Atmosphere, Vol. 8(12), 248.
Liu, C., Tang, S., Shen, L. & Dong, Y. (2017), “Characteristics of turbulence transport for momentum and heat in particle-laden turbulent vertical channel flows,” Acta Mechanics Sinica, 33, pp.333-845.