Fluid-Structure Reaction Study of an F-16 Limit Cycle Oscillation Case with Stores

Abstract

There exists a significant need for a detailed understanding of the physical mechanisms involved in limit cycle oscillations (LCO) that can lead to a unified theory and analysis methodology. This work aims for a more thorough comprehension of the nature of the nonlinear aerodynamic effects for transonic LCO mechanisms, providing a significant building block in the understanding of the overall aeroelastic effects in the LCO mechanism. Examination of a true fluid-structure interaction (FSI) LCO case, i.e., flexible structure coupled with computational fluid dynamics (CFD), is considered quasi-incrementally since this capability does not yet exist in the flutter community. The first step in this process is to perform fluid-structure reaction (FSR) simulations, examining the flow-field during rigid body pitch and roll oscillations, simulating the torsional and bending nature of an LCO mechanism. The next step is to perform FSR simulations of the flow-field during prescribed aeroelastic structural modes. Through this build-up FSR approach, valuable insight is gained into the characteristics of the flow-field during transonic LCO conditions in order to assess any possible influences on the LCO mechanism. This will be accomplished temporally via traditional flow visualization techniques combined with Lissajous and wavelet analyses. By examining the effects that the flow features have due to the structure, including stores, these analysis techniques will lead to the ability to predict whether LCO is expected to occur for particular configurations, and aid in the stores clearance process.