Development and Validation of an Augmentation to the Commercial CFD Software FLUENT™ Enabling the Tracking of Ellipsoidal Particles in Low Reynolds Number Flows

A majority of the commercially available computational fluid dynamics packages are equipped with a module for Lagrangian tracking of spherical particles. No such module exists in an off-the-shelf product enabling the Lagrangian tracking of ellipsoidal shaped particles. This work took advantage of the user defined function facilities provided in FLUENT™ to gain this capability. Three user defined functions were implemented to transpose the spherical geometry to an ellipsoidal geometry. The orientation of the ellipsoid was determined by numerically solving the equations of rotational motion. Hydrodynamic drag was taken to be a function of Reynolds number and orientation. Two tests were performed to validate the rotational and translational motions of the ellipsoid in low Reynolds number flows. First, a simple shear configuration was examined with a single particle suspended at the center of the domain. The particle was allowed to rotate without translation. This was repeated for several particle sizes and flow rates and the simulated time for the particle to perform a single rotation was compared with the theoretical findings of Jeffery (1922). The results showed strong agreement for the range of particle sizes and flow rates examined. Second, a horizontal pipe with circular cross-section setup was simulated. Particles were injected from the pipe inlet and their motions were analyzed. Deposition efficiency was shown to be a function of aspect ratio and dimensionless relaxation time. Strong agreement was shared with a previously published empirical expression.