The migration and segregation of particles in suspension is of great significance in a range of biomedical applications. These include the margination of medication in the blood stream so that it may be absorbed at the artery walls (e.g. the BCG vaccination for tuberculosis) and the focusing and separation of cells in microfluidic devices (e.g. isolation of circulating tumour cells).
The aim of this project is to develop and validate a computational test bed that captures the relevant fluid-particle dynamics and then apply it to explore opportunities for improving material and device designs in these applications. The lattice Boltzmann method (LBM) will be used to describe the mechanics of the carrier fluid, with either Newtonian or non-Newtonian rheology, while the discrete element method (DEM) will represent suspended particles. Recent improvements to the partially saturated method (PSM) will be used for hydrodynamic coupling between the LBM and DEM. Computations will be launched on high performance computing (HPC) infrastructure. Once validated, the model will be used to study the influence of flow geometry, flow reversal, fluid rheology, particle shape, and solid volume fraction on the rate and degree of transverse particle migration and segregation/focusing.
The non-Newtonian characteristics of blood will be captured using the Kuang-Luo rheological model. The irregular shape of transported particles (e.g. red blood cells are best described as biconcave discs) will be mimicked using clumps of rigid spheres. To enable fully resolved, direct numerical simulation of the hydrodynamics, periodic geometries will be utilised. This will facilitate extensive sampling of the parameter space in each simulated application.
The successful completion of this project will provide new insight on the geometrical and material parameters which dominate particle separation in suspension flows. This information is difficult to extract in vivo or from experiments. The application of the developed model will answer questions such as:
1. How does the degree of flow reversal in an artery, which is a function of the local blood pressure and artery diameter, affect the transverse migration of medications in the blood stream to the artery walls?
2. Is the complex shape of red blood cells and other suspended particles critical to the degree of migration and segregation that occurs in the blood stream?
3. How can the rheology of the carrier fluid be engineered to improve cell focusing and separation in microfluidic devices?
4. What level of geometric complexity is necessary to effectively separate target cells/particles in a microfluidic device, and is this influenced by flow reversal?
In addition to these focused outcomes, this project will generate fundamental new knowledge in fluid-particle mechanics which has implications for a broad range of problems in science and engineering.