The unsteady aerodynamic-dynamic interaction of a tethered bluff body is of vital importance to military and life-saving operations. Bluff bodies are encountered as airdrop, low altitude parachute extraction systems, and slung load packages, as well as comprising static and dynamic structures around which rotorcraft maneuver. Interactions between flow-induced forces/moments, inertial and elastic characteristics of the loads, and the handling qualities of the vehicle itself, can lead to large and divergent oscillations of the loads and pose threats to safety. Fundamental issues include the causal physics of unsteady, turbulent wakes of static and dynamic bluff bodies. As a first step, wind tunnel experiments have been performed using two generic shapes, a rectangular box and a cylinder of small aspect ratio. Dynamic behavior has been studied with various levels of inertia and various types of tethers, correlated with some full-scale flight test results and prior research on these generic shapes. Measured divergence speed is seen to reasonably scale to full-scale flight test results on tethered rectangular box shapes. Quasi-steady loads exhibit a sharp sensitivity of side force and yawing moment over some ranges of yaw angles, associated with the separation location. Computed frequencies appear to scale with Strouhal number over a wide range of Reynolds number.
Stability prediction of sling load dynamics using wind tunnel models
Stabiltätsvorhersage der Pendellastdynamik durch Windkanluntersuchung
2011
13 Seiten, 16 Bilder, 14 Tabellen, 25 Quellen
Conference paper
English
Stability Prediction of Sling Load Dynamics Using Wind Tunnel Models
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