Investigations Of Flutter Characteristics Of A Wing-store System With Complex Connection Features

The aeroelastic problem related to the wing-store system affects the flight dynamics of modern aircraft.Some wing-store configuration can seriously affect the flight characteristics of aircraft,e,g.significant reductions in the flutter speed boundary of aircraft,which can affect the normal combat or operational performance of the aircraft.When the wing or wing-store system has nonlinear characteristics,the flow airflow can appear interactions with its own structure during the flight process.There will generate a certain period of constant amplitude oscillation before the critical speed of the flutter and this oscillation will not diverge.This phenomenon is called limit cycle oscillation(LCO),it can influence the stability of the pilot's operation significantly.So it is valuable to recognize the dynamic and aeroelastic characteristics of the wing-store system,especially the aeroelastic problem of the wing-store system with nonlinear characteristics.This paper studies the flutter characteristics of a wing-store system with complex connection features in order to figure out influence of store pitching stiffness to the flutter characteristics.The main contents are as follows:Firstly,an unsteady aeroelastic analysis method of the wing-store system was proposed,which included both linear unsteady analysis method and nonlinear analysis method.It can provide theoretical basement of the design,simulation,fabrication and experiment of the present flutter wind tunnel test model.Secondly,a design method of the flutter-store system flutter wind tunnel model was proposed.With the completion of the design process,the composition of the flutter-store system flutter wind tunnel model,its quality,its stiffness,its dimensional properties and connections of every components were proposed.The working principle of the nonlinear connection of the store pitching free-play was analyzed.An actual wind tunnel model was manufactured based on the design.Basic modal frequency and vibration modes of the present model were measured with ground vibration tests.The tested results were serveed as the reference for the rear simulation results and flutter wind tunnel test experiments.Thirdly,a finite element model was established by MSC.Nastran/Patran software according to the structural design of the present wing-store system and flutter wind tunnel test model.Structural dynamics analysis and flutter calculation were then carried out.Influence of the store pitching stiffness on the flutter characteristics of the linear state of the present wing-store system and the influence of the store aerodynamic force model on the flutter characteristics of the present wing-store system were comprehensively analyzed.Finally,A series of wind tunnel tests were carried out for the wing-store linear connection state and store pitch free-play nonlinear state,respectively.Also,some experiments were completed to investigate the influence due to the store pitching stiffness parameter variation and the pitch free-play size parameter variation.