Abstract

Motion of spheres falling through fluids is a classical problem in fluid mechanics. The problem is solved for steady motion and other special cases such as for small and large Reynolds numbers, but not yet for transitional flows due to a complicated nonlinear drag relationship. However, in recent decades a new approach has become available for study- ing this problem via the development of powerful processors and computers. In this thesis we investigate free falling of spherical shape objects through fluid media. We produce ex- perimental data and then model the motion mathematically via Newton’s second law and the Navier-Stokes equations. The resulting second order non-linear differential equation has been solved numerically. Finally, by using the fluid-structure interaction method (im- mersed boundary method) we simulate the free fall of spheres in water and compare these results with our experimental data. The aim of this study will be to answer how density, viscosity, temperature and gravitational acceleration affect the rate of descent of a solid body through a fluid.