| When the aircraft is flying in the clouds containing supercooled water droplets, these dropletsimpinge on the surfaces of the lift components and then freeze. The ice accretion on these componentsis one of the potential hazards in flight, and can lead to air crash. Icing research tunnel is not availablein China now, so the major focus of current research is numerical simulation of aircraft icing. Afterreferring and studying many domestic and foreign literatures, modular icing codes have beenestablished using VC/FORTRAN mixed programming and DLL technology, and the software packagecalled NUAA-ICE3D is well developed to perform normal functions of these modules based on MFCframework. In addition, some ideas and new methods are also presented. The main research andachievements of this thesis are as follows:At first, grid generation and reconstruction for calculation of airfoil ice accretion on cylinder,single and multi airfoils are studied carefully, and it is a very efficient and feasible way to generate thegrid by solving the elliptic PDEs. The forcing terms are automatically chosen in the manner ofHilgenstock method such that orthogonality and spacing control on the icing smoothed boundary areachieved. In order to obtain the appropriate structured grid for the wings and wingbody models, twokinds of grid reconstruction method are introduced; they are H-type grid around the wing and O-typegrid on the end face of the wing tip. Taking account of ice accretion on the upwind surfaces of the liftcomponents such as wings, in order to improve the efficiency, quality and reliability of grid,ellipse-shaped and fan-shaped partition methods have been introduced and validated. Finally, the gridgeneration and reconstruction can be carried out successfully during the calculations of ice accretionbased on these new techniques.The flow field solver based on the density pattern is developed in this thesis which can be used tosolve the Euler/Navier-Stokes controlled equations. In this code, the modified central differencemethod with artificial viscosity by Jameson scheme is applied for spacial discretization and an explicitfour/five stages Runge-Kutta seheme is used for temporal discretization. The convergence procedure isaccelerated by using local time step and implicit residual smooth technology. In order to calculate theturbulence viscosity coefficient, three turbulence models, zero-equation B-L model, one-equationSpalart-Allmaras model and two-equation k-ε model, are employed in this thesis. After this, thevalidation and analysis of the developed solver are carried out.Two classes of methods for supercooled water droplet impinging calculation are adopted in thisthesis; they are Lagrangian and Eulerian methods. In the Lagrangean formulation, the grid topologicalrelation is employed to seek the spatial location of water droplet and the grid partition method is usedto set the time step for discretizing the governing equations of droplet, which has resolved thetime-consuming problem. In addition, three discretization approaches including Euler method, estimatealong with adjustment method, and four stages Runge-Kutta time stepping scheme are employed todiscretize the time term of the momentum equations. In Eulerian approach, the UDF codes for solvingtransport equations for momentum and phase volume fraction are developed by integrating the UserDefined Scalar. For the sake of the UDF codes, some classic models are tested here such as airfoils,sphere, DLR-F6wing/body model, DLR-F6wing/body/pylon/nacelle model. Based on the automatic script function of FLUENT software, a series of encapsulation for loading the UDF codes, setting theinitial conditions, monitoring the iteration residual value are completed by using the MFC framework.This thesis gives systematic study on the process of ice layer accretion, especially the mass andenergy transfer between two-phase distribution (air and water droplet) and icing build-up region alongthe surface of airfoil. Based on the theory of momentum and thermal boundary layer, the governingequations are established by considering the conservation of mass and energy in each control volume.The developed code for calculating the ice-layer accretion is called ICEC module. Taking the cylinderas the example, this thesis also studies the effects of roughness height on the heat and mass transferamong the air, water film and ice, together with the final ice shape in the ice-layer accretion module. Anew correction model for roughness height is given to measure the rough characteristics of roughnessalong the iced surface more accurately. In this model, the roughness height is regarded as a function oficing condition, spatial coordinate, and icing time step by considering the local curvature of icedsurface. Based on the icing software developed, the effects of several key parameters on heat transfercoefficient and ice shape are presented, and these factors include free-stream velocity, statictemperature, angle of attack and the roughness height of surface, and so on. At last, the prediction ofthree-dimensional ice shape is implemented based on the two-dimensional analysis.In order to improve the capability of integration and users orientation for icing software, thedetailed study on the development of the icing simulation software is given in this work. Thecalculation of ice accretion is devided into four modules; grid generation and reconstruction (GRID),flow field calculation (FLOW), particle trajectory and impingement calculation (DROP),thermodynamic and ice growth calculation (ICEC). At first, a new module programming method isused to convert the source code into the file format called Dynamic Link Library. Then, a multi-threadsimulation platform is designed based on the MFC framework to execute related functions, includingthe implement of each module, data storage, data communication, displays of results and so on. Besides,two execute modes are adopted in icing calculations in order to simulate the multiple ice-layersaccretion. It is found that these methods used in this work have made the software efficient and easy tobe updated. The validation and robustness of the software are also well tested. In addition, theFLUETN flow solver and UDF codes for calculating the water droplet impingements are alsointegrated into our software. All the initial conditions can be input via the user interface.The functions of the key parts of ice tunnel are described in this thesis, and the full size of icetunnel and the turning vane are designed together based on the wind tunnel design principle. Thesecharacteristic parameters including total pressure, static pressure, and velocity are computed for all thesections in the different locations of ice tunnel. As the ice tunnel has been designed, three-dimensionaldiagram is drawn clearly. In order to decrease the pressure loss in the turning period, three kinds ofturning vanes which sections are airfoil, arc-line, and arc shape are well designed to fit the demands oftunnel corners. Then, the numerical simulation of flow field for the first expanding section, first turningsection (including nine vanes) and transition section is completed when the inlet condition is V=80,100,120m/s, and t=-30℃. The design features and flow qualities near this corner are discussed. |
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