A New Forced Oscillation Capability for the Transonic Dynamics Tunnel

David ,1. Piatak and C aig S. ClecknerNASA Langley Res, arch CenterHampton. '/AAIAA 2002-0171ABSTRACTA new forced oscillation system has boon instMledAnd tested at NASA Langley Research Center's Tran-s()ni(: Dynamics Tunnel (TDT). The system is kllownas the Oscillating TurntAble (OTT) and has been de-signed for the ImrI)ose of oscillating, large senfispanmodels in pitch at frequencies up to 40 Hz to acquirehigh-quality unsteady pressure And loads data. Pre-cisely controlled motions of a wind-tunnel model onthe OTT can yM(l unstea(ly aerodynamic t)henomelmassociated with flutter, limit cycle oscillations, shockdynanfics, an(1 non-linear aerodylmnfic effects on manyvehicle configurations. This paper will (liseuss thegeneral design and eonlponents of the OTT and will1)resent test (tata from 1)erformance testing and fromresearch tests on two rigid senfispan wind-tunnel inod-els. The research tests x_re designed to challenge theOTT over a wide range of operating conditions whileacquiring unsteady t)ressure data on a small rectangu-lar supercritical wing and a large supersonic transportwing. These results will be presented to illustrate theperformance capabilities, consistency of oscillations,and useflflness of the OTT AS a research tool.INTRODUCTIONToday, An aircraft's structure tends to 1)e conserva-tive in strength for ninny reasons, including tile lackof accurate flutter t)rediction codes. If one can accu-rately predict the flutter and other aeroelastic charac-teristics of an aircraft before it is constructed, the air-(:raft wing structure could be ot)tiinized from the per-spectives of flutter, strength, and weight. However,many incidences of aeroelastic shortcomings are iden-tiffed and ad(lressed After An aircraft's first flight dueto the challenges, especially in the transonic regime,of t)redicting the complex interaction of aerodynamicforces, elastic forces, and inertial forces. Ac(:u-rate aeroelastic analyses require rigorous Inodelling ofthe unsteady aerodynamic environment at transonicspeeds and high reduced frequencies.