| Résumé | The development of a non-dimensional performance parameter, describing the lift air flow required for an air cushion vehicle, was the purpose of this project. The Lift Air Coefficient had to be easily modified to account for planform geometry, the arrangement of plenum and vegetation encountered. The results of a theoretical analysis of planform effects were checked experimentally, while vegetation and clustering effects were related to Lift Air Coefficient by an empirical relation developed after tests were run.
Vehicle shape was found to have the most important planform effect, while clustering changed the coefficient by very little. The shape factor used was a ratio of the square root of the planform area to the total perimeter. Vegetation of uniform density was accounted for by a modification of the coefficient by a ratio of vegetation height to the height above ground of the same material under a heavy weight. Due to a leakage problem, the accuracy of the Lift Air Coefficient values was poor in the lowest hoverheight region.
The coefficient proved to be easily modified to allow for many variables, but it was noted that many restrictions imposed were unrealistic. |
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