On the Heaving Motion of Circular Peripheral Jet Ground Effect Machines

Abstract

The heaving motion of peripheral jet ground effect machines with circular planform has been studied and the simple expressions of the equation of motion are formulated. The analysis is separated into two parts, i.e. the original peripheral jet configuration and the modified configuration equipped with the stability jets. In both cases, the behavior of the jets is quantitatively treated as the “underfed” and the “modified overfed” operation and after some simplification, second order nonlinear differential equations are derived as the equations of heaving motion. Those equations are still valid for a large amplitude heaving oscillation or for a large initial hover height. Furthermore, the frequency and damping characteristics of the small amplitude heaving oscillation can be predicted by the linearized equations of motion which are derived by the use of the approximation of small amplitude. The agreement between the analytical and experimental results is found to be comparatively good.