Aerodynamic Active Vibration Alleviation for Buffet Excited Vertical Tails
Abstract
The efficiency of an active auxiliary rudder system in alleviating fin buffeting is investigated based on extensive low-speed wind tunnel tests. A modern fighter aircraft model of 1/15th-scale is used to represent a single-fin configuration of canard-delta wing type. A specific vertical tail is fabricated featuring a digitally controlled auxiliary rudder providing harmonic oscillations. The vertical tail is instrumented to measure unsteady surface pressures, fin tip accelerations, and auxiliary rudder moments. Open-loop tests show that the fin's unsteady pressure field is feeded with energy at the frequencies of the auxiliary rudder motions. With increasing frequency and deflection angle the rms surface pressures are shifted to higher levels even at high incidences. Therefore, closed-loop operations may reduce buffet loads by approximately 18 percent. A nearly constant rudder moment over the angle-of-attack range investigated substantiates the effectiveness of the auxiliary rudder concept also at high-alpha. The active control system employs single-input, single-output control laws to alleviate buffeting in the first fin bending and torsion mode, respectively. Controller efficiency and stability parameters are evaluated using dynamic system simulations. The studies demonstrate that with active control fin tip acceleration spectral density peaks at the frequencies of the first fin eigenmodes can be reduced by as much as 60 percent at angles of attack up to 31 degrees. (20 figures, 23 refs.)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 2003
- Accession Number
- ADA419135
Entities
People
- Christian Breitsamter