Experimental Investigations of Buffet Excitation Forces on a Low Aspect Ratio Trapezoidal Half Wing in Incompressible Flow.

The paper addresses the problem of determining the steady and unsteady airloads on swept wings of low aspect ratios at high incidences. Despite great progress in the field of computational fluid dynamics, this problem is not yet accessible to computer- supported methods, at least with respect to unsteady airloads. First, the information will be discussed which is necessary for buffeting prediction. The reason for performing pressure measurements are outlined. A brief description of the test set-up and instrumentation is given

Measurement of Unsteady Airloads on an Oscillating Engine and a Wing-Engine Combination.

Experimental investigations of unsteady aerodynamic forces were performed on an oscillating ejector engine model and a wing/engine combination in the subsonic and transonic flow regimes. The experimental results were compared with theoretical results. The aim was to determine how well, in reality, the mathematical aerodynamic models commonly used for flutter calculations correspond to the flow conditions on an engine. The investigations on the isolated ejector engine demonstrated that linear lifting surface theory provides quite accurate unsteady aerodynamic forces. The effects of the Mach number and reduced frequency are described correctly. For the wing/engine combination, the unsteady interference effect of the 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 induced by the engine on the wing are small and are therefore of minor influence on the unsteady airloads of an oscillating wing

Measurement of Steady and Unsteady Airloads on a Stiffness Scaled Model of a Modern Transport Aircraft Wing.

Extensive wind tunnel tests have been carried out on a modern transport aircraft wing in transonic flow. The objective was to measure steady and unsteady pressure distributions, and to investigate the influence of the variable twist distribution of an elastic wing. For this purpose the wind tunnel model was scaled in stiffness, so that the twist distribution was similar to a representative aircraft, and changed with loads variation. The extensive model instrumentation consisted of opto-electronical equipment to measure the actual wing twist distribution. The forced model oscillation in pitch and bending up to a reduced frequency of about 0,7 (based on a reference chord) was measured with conventional accelerometers. A piezo-electrical balance was used for steady and unsteady forces measurement. Steady and unsteady pressures were measured simultaneously with 290 pressure transducers. Investigated parameters were Mach number, stagnation pressure, angle of incidence, reduced frequency and oscillation amplitude

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

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