Computing Flows Around Rotor By Using Time-depended Adaptive Grid Based On Unstructured-Cartesian Overset Mesh System

As a unique type of aircraft,helicopter has great application value in many aspects.As a main aerodynamic component of a helicopter,the rotor has great influence on the flight performance and noise level of the helicopter.Therefore,the researches of flow field simulation and aerodynamic analysis for the rotor is of great significance.The first chapter mainly describes the current research status in related fields both at home and abroad,involving grid technologies and solution technologies related to rotor flow field simulation,and introduce the main work of this paper.The second chapter mainly includes main equations in CFD,spatial discretization,time discretization,turbulence models,control equations in ALE form,preconditioning method for low speed and boundary conditions.The third chapter introduces unstructured overset grid technology for the solver of cell-centered scheme and the related technologies,such as searching the host cell,calculating the distance to the wall and exchanging the data between different grids are introduced.The method here can handle grids with different numbers,different shapes and different coverage relationships.It is efficient and can be used to different situations.In addition,some structure grid,unstructured grid generation technologies and overset grid technology based on structure grids are introduced.The fourth chapter introduces the background grid initialization,adaptive criterion,adaptive algorithm,data structure and the method dealing with the Cartesian grid cells.Adaptive refinement and adaptive coarsening can be carried out in time according to the information of the rotor flow field.The fifth chapter introduces the method of describing the mesh motion of rotor,the trim method for articulated rotor in different situations,conductions of some examples to verify the method.In the sixth chapter,simulations,verifications and comparisons for double airfoils and different rotors in different conditions were conducted.The results show that the technologies here can simulate the rotor flow field and dynamic characteristics effectively,the time-depended adaptive grid technique can improve the capture result of tip vortex in the rotor flow field significantly.