Numerical Simulation Of Icing Based On Three-dimensional Cartesian Grids

Aircraft icing for aircraft flight safety is a serious threat,so it is necessary to research on aircraft icing phenomenon.This paper provides a method for numerical simulation of ice accretion of a three-dimensional Cartesian grid,the grid generation,flow and droplet trajectory calculation and droplet impingement,ice model and so on.The main contents of this paper are as follows:Firstly,the three-dimensional Cartesian mesh generation method and flow field calculation method are studied.Using Octree Data structure,this paper introduces the methods of neighbor search,grid type determination,mesh reconstruction and virtual element method to deal with the boundary conditions of three-dimensional objects.The three-dimensional Euler equation is used to solve the governing equation and discreted on spatial and temporal domain,and the artificial dissipation term is introduced to suppress numerical oscillation,and the local time step method is used to accelerate convergence.Finally,a numerical example is given to verify the correctness of the proposed method,and it is concluded that icing has a bad effect on the aerodynamic performance of aircraft.Secondly,the calculation of water droplet trajectory is studied.The Lagrange method is introduced to solve the water droplet trajectory.The retrieval method of droplet location in Cartesian grid and the location of Impact Point between Water Drop and Three-dimensional Object Surface are studied.The local droplet collection coefficient of the surface element is calculated and compared with the experimental data to verify the correctness of this method.Finally,the calculation of ice on three-dimensional surface is studied.A three-dimensional freezing mathematical model is established,and the meanings and solving methods of the mass and energy conservation equations of the model are expounded.The convective heat transfer coefficient is calculated by the correction method based on the principles of air pressure gradient and shear stress distribution.The amount of ice is solved by the correction iteration method.The growth of the ice surface unit is carried out at all points.A number of calculation results are obtained for airfoils under different icing conditions to verify the correctness of the icing model and to clarify the influence of temperature and angle of attack on the ice shape,and to verify the advantages of the multi-step method.