Numerical Simulation Of Wing Icing For Natural Icing Flight Test

When the aircraft passes through the clouds containing a large number of supercooled water droplets,the phenomenon of aircraft icing will occur,which seriously affects the flight safety.The airworthiness regulations require the aircraft to conduct a natural icing flight test before putting into operation.In order to guarantee the safety and smooth going of the natural icing flight test,it is necessary to use numerical simulation method to predict the icing situation of the aircraft before the flight test.Since the state parameters of the clouds during the flight test will change with time,the numerical simulation of icing is required to be completed within a limited time.In addition,there are many uncertain random factors in natural icing conditions,which should be considered in numerical simulation.In view of the above two requirements,the following two research objectives are proposed.First,a fast calculation method of droplet trajectory is to be proposed.Then,Uncertainty quantization(UQ)analysis is to be carried out to analyze the impact of randomness of droplet size on the shape of icing.The detailed works of this paper are list as follows.Firstly,an icing numerical simulation program is developed based on Messinger model.The water droplets trajectories are calculated by Lagrange method.Convective heat transfer coefficient is evaluated by S-A model which takes equivalent sand grain roughness into account.The radial basis function interpolation mesh deformation technique is used to obtain the computational mesh after icing.The comparison of simulation and experiment results shows that the program is capable of simulating frost ice,glaze ice and mixed ice.Secondly,the fast method for calculating the droplet trajectory is studied based on the developed program,and a two-stage interpolation method based on Lagrange method is proposed.The first stage interpolation is the collection coefficient interpolation,which only which only calculates the collection coefficients of part of the wall grids,and obtains the collection coefficients of all grids through interpolation.The second stage interpolation is the interpolation of water droplets trajectories.Only a small portion of the water droplets trajectories are calculated in the far field and the trajectories of all water droplets are calculated by interpolation on the near wall surface.The results show that the calculation efficiency of the present method is one or two orders of magnitude higher than the traditional method.Lastly,based on Monte Carlo method,an algorithm and program are constructed to consider the influence of random droplet size on icing through uncertainty analysis.The results show that the possible icing range given by this method convers the main part of the experiment values,which verifies the reliability of this method.This work provides a numerical prediction method for judging whether the amount of ice in natural flight test environment meets the requirement of airworthiness regulations and whether it exceeds the safety range of the aircraft.