Numerical Simulations For Flowfield Of Tilt-rotor Based On Adaptive Grid Method

The high precision of numerical simulation of the rotor/wing interaction flowfield in hover isvital for the accurate prediction of aerodynamic performance of the tilt-rotor aircraft, thus it hasalways been a hotspot and difficulty in the field of helicopter aerodynamics. Aiming at improving thesimulation accuracy of the rotor/wing interaction flowfield and blade-tip vortex of the tilt-rotoraircraft, a multi-block adaptive grid method is proposed and employed for numerical simulations ofthe tilt-rotor flowfield in this paper. After that, the aerodynamic characteristics of “Caradonna-Tung”and UH-60A rotors have been simulated by the presented method to verify effectiveness of the CFDmethod. On these bases, the effects of different structure parameters on the rotor/wing interactionflowfield are finally investigated for the tilt-rotor aircraft. The main research contents are as follows:In Chapter1, the necessity of research of the tilt-rotor aircraft is emphatically introduced, and thecharacteristics of tilt-rotor aircraft is analyzed, and the developments of the CFD technique in thenumerical simulation of helicopter and tilt-rotor aircraft flowfield have been described also. Inaddition, it is demonstrated the importance of the adaptive grid technique to benefit the calculationprecision and computing resource reasonable utilization for simulation of tilt-rotor flowfield.In Chapter2, according to the blade motion characteristics of tilt-rotor/wing interaction condition,the method for the grid generation of tilt-rotor airfoil is firstly established, and then an automaticmethod of formulation of blade grid is then put forward, which is suitable for the simulation thetilt-rotor/wing interaction flowfield. After that, some corresponding grid examples are generated bythe method.In Chapter3, the CFD simulation method for predicting unsteady flowfield of tilt-rotor isestablished. The governing equations are Navier-Stokes equations, and the scheme of Roe-MUSCL isused for spatial discretization, and the scheme of explicit Runge-Kutta is adopted for temporaldiscretization, and the Baldwin-Lomax model is chosen to close the N-S equations. For the unsteadyflowfield, the dual time method is employed to simulate the tilt-rotor/wing interaction flowfield. Themoving-embedded grid system and flowfield analysis are generated and verified by several test cases.In Chapter4, in order to improve the precision of the tilt-rotor flowfield calculation, amulti-block adaptive grid algorithm is put forward. Then, the flowfield and blade-tip vortexcharacteristics of Caradonna-Tung and UH-60A rotors in hover are correspondingly simulated by themethod. To investigate the effects of the tilt-rotor/wing structure design parameters on thecharacteristics of the interaction flowfield such as force distribution, the pressure coefficient distribution, and interaction vortex flowfield, a combined rotor and wing model is especially designedas a comparative example. Some new results are then obtained through the comparative analyses.In Chapter5, the effects of the different structure parameters on tilt-rotor/wing interactionflowfield in hovering are investigated by using the multi-block adaptive grid algorithm. Throughcalculations and analyses of the influence of the three rotor/wing parameters (distance between rotorand wing, wing half span, the wing sweep angle) on the tilt-rotor interaction flowfield, somemeaningful conclusions are obtained.