Unsteady Aerodynamic Characteristics For The Aircraft Oscilation In Large Amplitude

There are three parts in this thesis to study the unsteady aerodynamic characteristics for the aircraft oscillating in large amplitude. The first is the wind tunnel test technology. The second is the unsteady aerodynamic characteristics and modeling of the aerodynamic. The third is the influence of the unsteady aerodynamic characteristics to the maneuvere flight.First of all, a dynamic test equipment of two freedoms was developed in NH-2 low-speed wind tunnel at Nanjing University of Aeronautics and Astronautics. The dynamic test equipment not only can be used to simulate the pitching, rolling and yawing motion of the aircraft around its body axes, but also can be used to simulate the pitching-rolling and yawing-rolling coupled motion. The rolling motiom in no side slip around the velocity axes can be simulated by adjusting the yawing angle and rolling angle amplitude. The wind tunnel wall influences to the unsteady aerodynamic was investigated. It is indicated that the magnitude of the wind tunnel wall influences for lift force is about 4.1% for the test model with 4.87% block capacity. In this thesis, the mothed of dynamic derivative simulation is developed using the unsteady aerodynamic data obtainded by wind tunnel tests in which the test model oscillating in large amplitude and the simulated results were compared with the dynamic derivative obtaineded in convention dynamic derivative test.On the based of test data, the unsteady aerodynamic characteristics of the BJ-1 aircraft model and the BJ-2 aircraft model were studied. It is indicated there is an essential distinction for the unsteady aerodynamic characteristics between single free motion and coupled motiom. At the large angles of attack, the unsteady rolling moment characteristic appears hypostasis difference between pure rolling or yawing motion and coupled motion. At the other hand, the unsteady aerodynamic characteristics of the two configurations are different greatly.Secondly,in order to applying the unsteady wind tunnel test data to the study of maneuvere flight, the aerodynamic modeling and the aerodynamic mathematic model were investigated. In this thesis, the fuzzy logic is used to study the aerodynamic modeling. The advantages of this mothed are that the variables of the model aren't limitied, the process of modeling is pure mathematic, it is convenient to calculate the unsteady aerodynamic based on the mathematic model. It is indicated that the modeling results can reflect the characteristics of aerodynamic. The suitability for the linear superposition model was investigated based on mathematic modeling. It is indicated that the superposition model isn't suitable at the large angles of attack.At last, the influence of the unsteady aerodynamic characteristics to maneuvere flight was investigated. The equation of six freedoms was used to simulate the flight orbits with the unsteady aerodynamic obtainded from the linear superposition model and the coupled motion tests and the two simulation results were compared. It is indicated that there are large difference between the two results, because their aerodynamic damp characteristic are opposite. Using the unsteady aerodynamic obtainded from the linear superposition model, the simulation orbits are steady, but they are unsteady using the unsteady aerodynamic obtainded from the coupled motion tests. The result can be used to explain the lateral-directional oscillating of F-16 configuation appeared at flight test.