Limit cycle oscillaton prediction for aircraft with external stores – IFASD 2019

The objectives of this work is to develop a truly limit cycle oscillation (LCO) predictive tool in the Nonlinear Aerodynamic and Nonlinear Structural Interaction (NANSI) module of ZONA Euler Unsteady Solver (ZEUS). A novel Nonlinear Structural Damping (NSD) model has been developed that can be included in the NANSI module to provide the NSD effects for LCO prediction of aircraft with stores configurations. The NSD model requires a single parameter, ?, that needs to be estimated from the flight test data to quantify the nonlinear damping level. Based on the values of ? estimated from seven F-16 store configurations, it was found that ? is closely related to the flutter frequency of the F-16 with stores, by the “? - estimator” equation. The flutter frequency of an eighth F-16 with stores configuration was first computed and the value of ? was determined using the ? -estimator so that it was not estimated by the flight test data. Using this value of ? in the NSD model to predict the LCO of the eighth F-16 with stores configuration at various flight conditions, a very good match with the corresponding flight test LCO measurements was obtained. Thus, the ?-estimator can be used for the LCO prediction prior to flight test of a new F-16 with stores configuration, rendering the NANSI module of ZEUS as a truly LCO predictive tool.