Pitching Characteristics of Peripheral Jet Ground Effect Machines

Abstract

A theory of the pitching characteristics is presented for three-dimensional peripheral jet ground effect machines which are equipped with a compartment partition along the pitch axis. The analysis is separated into two parts, i.e. the longitudinal static stability and the dynamic pitching motion. In both cases, the behaviors of jet are quantitatively treated as the underfed and overfed operation. At the static pitch condition, the cushion pressures in the falling downward and rising upward compartments are first discussed, and applying those results, a simple expression of the static moment about the pitch axis is derived. Next, utilizing the quasistatic principle, a second order nonlinear differential equation is obtained as the equation of pitching motion. Detailed calculations have been carried out for a circular model GEM, and the comparisons with experimental data are encouraging.