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Unsteady aerodynamic model of a cargo container for slung-load simulation

Published online by Cambridge University Press:  03 February 2016

L. S. Cicolani
Affiliation:
Army/NASA Rotorcraft Division, Ames Research Center, Moffett Field California, USA
J. G. A. da Silva
Affiliation:
Army/NASA Rotorcraft Division, Ames Research Center, Moffett Field California, USA
E. P. N. Duque
Affiliation:
Deptartment of Mechanical Engineering, Northern Arizona University, Flagstaff, Arizona, USA
M. B. Tischler
Affiliation:
Army/NASA Rotorcraft Division, Aeroflightdynamics Directorate, (AMRDEC) US Army Research Development and Engineering Command, Moffett Field, California, USA

Abstract

The problem of simulation models capable of predicting the aerodynamic instability of helicopter slung-load cargo containers and bluff bodies is addressed. Instability for these loads is known to depend on unsteady frequency-dependent aerodynamics, but simulation models that include the unsteady aerodynamics do not currently exist. This paper presents a method for generating such models using computational fluid dynamics (CFD) to generate forced-oscillation aerodynamic data and frequency domain system identification techniques to generate a frequency response from the CFD data and to identify a transfer function fit to the frequency response. The method is independent of the responsible flow phenomenon and is expected to apply to bluff-bodies generally. Preliminary results are presented for the case of the 6- by 6- by 8-ft CONEX (container express) cargo container. The present work is based on two-dimensional (2D) aerodynamic data for the CONEX side force and yaw moment generated by a forced oscillation in which frequency is varied smoothly over the range of interest. A first-order rational polynomial transfer function is found adequate to fit the aerodynamics, and this is shown to provide a good match with flight test data for the yawing motion of the CONEX.

Type
Research Article
Copyright
Copyright © Royal Aeronautical Society 2004 

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