Transonic Limit Cycle Oscillation Prediction From Simulated In-Flight Data

This paper investigates the transonic Limit Cycle Oscillation (LCO) phenomenon from a
computational/simulation point of view. A CFD/FE coupled solution is applied to a 3D model of a
rectangular wing with tip store (referred to as the Goland wing) in transonic flow, in order to study the
resulting LCO motions. The aim of the study is to develop a LCO prediction strategy from in-flight data;
at this stage of the work the data will be obtained from simulations. The effect of varying the thickness of
the Goland wing on the LCO onset flight condition is explored. The work then addresses the presence or
absence of nonlinearity prior to the onset of LCOs. This is crucial as the presence of any nonlinearity for
this type of wing can act as a telltale sign of impending LCOs. The clearance between the nonlinearity
onset flight condition and the LCO onset flight condition is quantified for various values of the wing
design parameters. It is shown that this clearance can be used in order to develop a useful ‘oncoming
LCO’ warning criterion.