Study of Rheological Behaviour of Spherocylindrical Particle Suspension via CFD-DEM: Formulation of Stress-Closure for Industrial Fluidized Bed Simulation

While colloidal suspensions of non-spherical particles have been studied relatively extensively, granular suspensions of non-spherical particles are rarely studied. The rheological behaviour of elongated granular particles is therefore not well known. This thesis deals with suspensions of rod-like particles of aspect ratio 4 subjected to shear flow in a low-density, highly viscous Newtonian fluid. CFD-DEM simulations for a periodic shear box have been performed for a pre-estimated range of shear rates and volume fractions. Dependence of rheological properties like shear stresses, relative viscosity, granular temperature, pressure and normal stress differences on the shear rate and volume fraction have been studied. These granular rods show shear thickening behaviour. The spherocylindrical particle suspensions experience less collisional stresses than spherical particles due to preferred particle alignment in the shear direction. Herschel and Bulkley [1] model is used to fit the collisional stress data. Two different regimes have been identified for granular suspension based on the flow index. Interestingly, a relatively large range of shear rates and associated stress can be expressed in the form of a simple equation based on Broughton and Squires [2] model. This stress closure will further be used in more coarse grid models like MP-PIC which can simulate an industrial fluidized bed reactors of non-spherical particles.