Transonic wind tunnel investigation of limit cycle oscillations on fighter type wings - Update

Abstract

Abstract : A wind tunnel investigation was conducted to investigate the unsteady aerodynamic aspects of transonic Limit Cycle Oscillations (LCO) on fighter type aircraft wings. This investigation is a cooperative effort of General Dynamics (Fort Worth) and the National Aerospace Laboratory (NLR) of the Netherlands which is funded by the U.S. Air Force and the Dutch Ministry of Defense. Two tests were planned and the first test, conducted during September 1991, was concerned with a wing body configuration with wing stores and was restricted to incidences below 10 deg. The second test, planned for March 1992, will be for a simple wing-strake geometry and will cover incidences up to at least 30 deg. This paper presents results from the first test with the objective to obtain unsteady pressures and forces necessary for identifying the aerodynamic nature of transonic LCO which is currently encountered on many fighter configurations. The wing panel was oscillated in pitch at amplitudes and frequencies typical of LCO for flow conditions in which significant shock-induced separation is encountered. Unsteady pressure data were obtained for the wing panel in terms of both harmonic components and time-histories to highlight the nonlinearities. Unsteady forces and moments measured on the wing panel as well as on each wing store were also obtained to indicate the level of contribution of each element to the overall unsteady wing loads for pitching motions.