Peripheral Jets in Proximity of the Ground

Abstract

The problem of the performance of a two-dimensional lifting unit with peripheral jet distribution in proximity of the ground is considered fully from a theoretical standpoint but with design considerations in view. The parametral dependence of the lift augmentation characteristic of the unit on a set of three basic parameters—namely, jet thickness, height from the ground, and jet curtain inclination—is examined fully. The effect of raking the jet nozzle exit line on lift is also considered. Compressibility effects in the case of a high-speed jet are briefly commented upon, and overall design guidance lines are suggested. The extension of this analysis to the problem of the peripheral jet with axial symmetry can be performed easily by means of the geometric transformation first suggested by H. R. Chaplin.