Lagrangian simulations of dense solid-liquid suspensions

The aim of this project is to develop a computational approach that allows for explicitly simulating the dynamics of millions of particles suspended in a turbulent liquid flow. The main challenge is the dynamic coupling between the solids and the liquid. With the number of particles we are aiming for, a direct, fully resolved approach, is computationally unfeasible. We therefore need to carefully and realistically model the solid-liquid interactions and verify each step in the modelling process.

The developed procedure will eventually be tested by applying it to the multiphase flow in mildly turbulent mixing tanks for which experimental data is available.

Dense suspensions of solid particles in a liquid phase find application in chemical and related engineering in catalytic reactors and other situations where intimate contact between solids and a liquid phase is required. Numerically simulating the flow and (heat and mass) transfer processes of solid-liquid suspensions is important for assessing process performance and supporting process design.
There is a spectrum of levels on which multiphase flows (of which solid-liquid suspensions only form a sub-class) can be simulated. At a coarse, macroscopic level the phases involved are considered interpenetrating continua and continuum equations (including models for the dynamic coupling between phases) are being solved. At the opposite (microscopic) side of the spectrum, everything is solved explicitly [1]. For solid-liquid suspensions it means that the mass and momentum balance equations of the liquid as well as the equations of motion of each individual particle are solved, and no-slip conditions are imposed on the solid-liquid interfaces. The latter type of simulations requires computational meshes that are at least one order of magnitude finer than the particle size, and thus only allow for simulating a limited number (order 10,000) of particles in a simulation.

The current project is about developing an intermediate level of simulations where we aim for simulating of the order of 10 million particles on coarser meshes (mesh size of the same order as the particle size). This requires careful considerations as of how to dynamically couple the dynamics of solids and the liquid.

The method will be applied to the solid-liquid flow in a turbulently agitated lab-scale mixing tank with solids loadings of up to 20% by volume for which experimental data is available for assessing the level of realism of the outcomes of a simulation.

The successful candidate should have, or expect to have, an Honours Degree at 2.1 or above (or equivalent) in Chemical Engineering, Mechanical Engineering, Applied Mathematics

Knowledge of: Fluid dynamics, numerical methods, (basic) computer programming