Added Mass of a Sphere in a Bounded Viscous Fluid

The validity of potential flow and Stokes viscous flow theory was investigated experimentally to determine the effect of a real fluid on an oscillating rigid sphere bounded by a concentric spherical shell. Added mass and damping coefficients were determined over a range of Stokes numbers of 400 to 3.5 × 105. Results of the experiments indicate that Stokes viscous flow solution is valid over this entire range of Stokes numbers for small amplitudes of oscillation and that the potential solution is approached asymptotically for large Stokes numbers. A simple apparatus is described that was used to accurately determine both added mass and damping coefficients.