Numerical Simulation Of Aircraft Icing Based On Szilder's Random-walking Model

Aircraft icing is one of the main hidden dangers of flight safety accidents.Predicting ice shape by numerical simulation is the basis of aircraft anti-icing/de-icing system design.At present,most scholars generally use Messinger model for ice prediction.But due to its macro continuity nature,it is difficult to capture the complex morphology of the ice surface and interior using this model.Therefore,the random-icing model with discrete characteristics is used to simulate the wing icing problem,and the automatic control of icing calculation and mesh updating is realized based on Fluent dynamic mesh technology.The main contents of this paper are as follows:(1)The flow field of NACA0012 airfoil is calculated by Fluent software,and the influence of icing surface characteristics on its aerodynamic performance is analyzed.The influence rule of single ice horn/ridge at different sizes,locations,shapes and flight Reynolds numbers is calculated and summarized.Aerodynamic parameters of NACA0012 airfoil's simulated ice shape and experimental ice shape are compared,and it is show that the traditional prediction results of traditional Messinger model underestimate the influence of ice surface characteristics on aerodynamic performance.(2)The Euler method is used to derive the governing equation of three-dimensional droplet motion,and the effectiveness of droplet impact calculation method in this paper is verified.The distribution of water collection coefficient of NACA0012 airfoil with different droplet diameters is calculated,which provides the precondition for ice prediction.(3)Based on Szilder's thought,a three-dimensional random-icing model is established which includes droplet motion model and local icing probability model.The factors affecting ice formation,such as convective heat transfer coefficient,lattice size and stochastic characteristics of the model,are briefly analyzed.Finally,the random-icing simulation of NACA0012 wing is carried out with single-step method.By comparing ice shapes and analyzing ice density and surface roughness,it is found that this model has the advantage of predicting rough discontinuous ice shape.(4)Fluent dynamic mesh technology is used to solve the problem of mesh reconstruction in the process of icing.The droplet impact program and random-icing program are embedded into Fluent in the form of UDF,and then the unsteady icing simulation of two-dimensional NACA0012 airfoil is carried out.Finally,the aerodynamic characteristics of aircraft after random icing are analyzed.