Analysis of the Dynamics of a Freely Falling Body in a Viscous Fluid: Computational Fluid Dynamics Approach

The dynamics of solid objects falling through a viscous fluid was studied. The forces that control the motion as well as the effects of fluid viscosity and object density were studied using an analytical model. Wall effect due to the presence of finite fluid boundaries was evaluated using CFD. Through further correlation of the CFD results, a functional approximation model required to predict the limiting condition for wall effect was developed. The analytical solution gave a good approximation of the forces that control the motion and some indications that the effect of fluid viscosity is paramount in resisting the motion of the solid particle in a viscous fluid. The CFD approach was able to evaluate the system more accurately and allowed for the effects of finite fluid boundaries on the object motion to be calculated successfully. The analytical results agree largely with that of the CFD obtained in the range of vessel internal diameter D ≥ 2m which corresponds to the region where wall-effect is insignificant. The theoretical models were validated using experimental data. © 2022 The Author(s)