Measurement of Unsteady Pressures and Forces on an Engine and a Wing/Engine Combination Including Jet Simulation.

Abstract

Experimental investigations on the unsteady aerodynamic forces were performed on an ejector engine model and a wing/engine combination in the subsonic and transonic flow regimes. The experimental results were compared to theoretical results. The aim was to determine how well the commonly used mathematical aerodynamic models for flutter calculations correspond to the actual relationships observed on engines. The investigations on the ejector engine demonstrated that linear lifting surface theory provides accurate unsteady aerodynamic forces. The effects of Mach number and reduced frequency are described correctly. For the wing/engine combination, the unsteady interference effect for engine oscillation on the lower side of the wing is strongly influenced by flow separation at the wing/pylon connection. In general, the unsteady aerodynamic forces on the wing are small and, at this order of magnitude, can be correctly calculated with the linear lifting surface theory.