Numerical Simulation Of Ice Accretion Based On Cartesian Grids

Aircraft ice accreting is one of the main threats for flight safety and has raised attentions among today's researchers.Using numerical approaches to predict the ice accretion is one of the major topics.A basic procedure of ice prediction is divided into four parts: the flow filed calculation,the droplets trajectory,the icing model and the mesh regeneration.In this thesis,an ice prediction method based on Cartesian grids was presented.Besides the ability to predict ice shape,it is capable of quickly adapting and refining according to the iced boundary.The mesh regenerated automatically,meanwhile the former calculation results of flow field are inherited,for the advantage of Cartesian grids' non-body-fitted feature.Hence the procedure is accelerated.The major study of this thesis was stated as following:A Cartesian grids generation code was developed.The ghost cell method was applied to offer proper boundary conditions.The quadtree structure was used for neighbor retrieving.An improved ray tracing method was developed to overcome the odds in geometries.The Eulerian equations was solved by density based on finite volume method.The solver was tested in compressible inviscid cases and was compared to clarify the feasibility.Jameson's central difference scheme was used along with artificial dissipation terms added.The Runge-Kutta explicit time marching method was applied in time discretization.In addition,the local time step method and OpenMP parallel computation were employed to accelerate converging.A droplet trajectory was evaluated using Lagrangian method and solved with Runge-Kutta method to reach the numerical solution.The ice shape was predicted according to the classic Messinger model.The boundary layer integration equation was used for convection coefficient calculation.The prediction result of this thesis is compared to the experiments results and corresponding cases from LEWICE and CIRAMIL.The comparison argued that the method presented is feasible and reliable.The adaptive grid method was applied to all cases mentioned in this thesis,the converging process is displayed to show the improvement of converging speed.The Cartesian grid has been successfully merged in ice prediction.The complete ice prediction code based on Cartesian grids has been compiled and proven to be feasible.This combination of two techniques are believed to be helpful and significant for relevant studies.