Measurement and Simulation of particle motion in forced turbulent flow

The transport of particles as solids, droplets or bubbles by turbulent flows occurs in a very large number of industrial and natural situations of great importance; the mixing and combustion of pulverized coal in coal fired stations, and the dispersal of pollutants in the atmosphere and in rivers and estuaries are such two examples. In such flows, very small neutrally buoyant particles follow the flow dynamics and are commonly used as tracers. However, as soon as the particle diameter is of the order of or greater than the dissipation length scale, the particle is no longer a flow tracer and its dynamics changes radically. While solving the dynamics of a particle freely advected in a turbulent flow requires the knowledge of all the forces acting on it, the determination of these forces is a long-standing challenge for finite-size particles. The combination of laboratory experiments and smooth particle hydrodynamics (SPH) simulations thus provides a unique opportunity to gain a better understanding. This project has such an objective.
This collaborative project will build on a project funded by an ARC DP grant that started in January 2016. The project studies the motion of finite-size particles in a turbulent flow using experiments and numerical smoothed particle hydrodynamics (SPH) simulations. Turbulence is generated by the stirring motion of a cylinder submerged in a tank filled with water and open to air at the top. The bottom of the tank is either flat or V-shaped. The tank contains four quasi-neutrally buoyant either spherical, cubical or cylindrical bodies and four buoyant bodies of similar shape that reside at or near the free surface. Monash experiments therefore significantly (and more realistically) differ from other experiments that use the Von Kármán setup where the flow is enclosed in smoothed walls, and advects only spherical bodies. This experimental work was carried out in the Geodynamics laboratory of the School of Earth, Atmosphere and Environment at Monash University. The motion of the bodies is recorded from two sides by two video cameras. This new initiative between Monash and the CSIRO will open new grounds in sharing the experimental data. An automated body tracking workflow will be developed at the CSIRO to provide the positions and velocities of the bodies. Subsequent analyses will be computed using Matlab at Monash University. Probability velocity distributions, phase averaged velocity field and residence time will be among the outputs that will be compared with the SPH simulations. Both two-dimensional and three-dimensional SPH simulations will be benchmarked against the experimental results. The two-dimensional simulations will be developed at Monash University while the three-dimensional SPH simulations will use the CSIRO code. The project will aim to publish the results as joint high quality journal papers.