Nonlinear dynamics of a segmented skirt air cushion
Abstract
This paper gives results from a simulation of the pitch-heave dynamics of an uncompartmented segmented skirt air cushion vehicle. The simulation includes nonlinearities associated with skirt-ground contact. As modelled, the system consists of a ducted fan discharging into a plenum chamber. Results from several system models are presented and compared for a laboratory vehicle. System models of fourth and sixth order are developed; a quasisteady fan characteristic is used and the sixth order model includes additional orders for a lumped inertance model of the ducting and a pneumatic capacitance model of the cushion. The skirt is assumed to be a massless membrane capable of supporting some force in compression and to deform according to a geometric theory on contact with the ground. Three different geometric theories are compared through their effects on vehicle statics and dynamics. Large variations are found for some of the system response parameters, for example, the pitch stiffness. Predictions of pitch stiffness and footprint area are compared with static data. Predictions for a large scale craft indicate significant dynamic effects resulting from the capacitance and inertance.
- Publication:
-
1985 Joint International Conference on Air Cushion Technology
- Pub Date:
- 1985
- Bibcode:
- 1985act..conf.....G
- Keywords:
-
- Cushions;
- Dynamic Models;
- Ground Effect Machines;
- Skirts;
- Air Flow;
- Duct Geometry;
- Equations Of Motion;
- Ground Effect (Aerodynamics);
- Engineering (General)