A Numerical Method On Dynamically Disturbed Flow Fields Of Tilt-Rotor Aircraft

The tilt-rotor aircraft is a new type aircraft which combines the advantages of vertical takeoff and landing capabilities, inherent to the helicopter, with the high forward speed and range of a fixed wing airplane. During the tilting process of rotor, the fuselage are in a complex unsteady aerodynamics condition. The study on the flowfield of tilt-rotor aircraft is a challenging and important subject in the field of Helicopter Aerodynamics. In the past, theoretical method and wind tunnel test are the main means to investigate this problems. However, theoretical research has poor precision and wind tunnel test has the abuse of high risk, high cost, long cycle. In recent years, the rapid development of computational fluid dynamics makes it widely used in dealing with these problems. The actuator model can reduce the computing resources in the basis of ensuring the essential attribute of flow field and improve work efficiency. Dynamic overset grid technique is very suitable to deal with unsteady flow fields of rotor, without mesh regeneration and can guarantee the mesh quality.First of all, the numerical methods are introduced, which contains spatial discretization method, temporal discretization method, boundary conditions, turbulence model, low speed preconditioning and so on. Then a numerical method to predict the flowfield of tilt-rotor aircraft based on the actuator model and overset grid technique is proposed. In this method, the influence of rotor is considered in terms of the momentum which impacts to the fluid around it. Considering the motion and control of the rotor under the actual flight environment, the rotor trim is taken into account in the simulation of the rotor flowfield. The conversion mode is simulated by using the overset grid method. Finally, the dynamic flowfield of tilt-rotor aircraft is analyzed by using the numerical method proposed in this thesis and the results show that the method is efficient and useful.