Improvement Of Smoothed Particle Hydrodynamics And Its Applications In Geotechnical Engineering

Smooth Particle Hydrodynamics(SPH)is a kind of pure meshless method with Lagrange properties, because of its unique nature of computational domain discretization and numerical discretization, it is suitable to solve the Engineering Science problem with free mobile interface and complex physical boundaries. comparing with the traditional grid numerical method based, it does not need to rely on the grid to computer-aided calculate and can avoid some computational problems due to the presence of grid when some problems are calculated, including tedious and time-consuming remeshing, mesh distortion and complicated computational domain discretization. At present Smooth particle method has successfully solved a variety of types of engineering and scientific issues, In this paper, the following research work is carried out on the basis of the theory drawback of the smooth particle method and its application in engineering practice:(1)SPH-FDM coupling algorithm is presented, namely Finite Difference Method (FDM)is coupled with the SPH algorithm, to revise particles approximation defects near the domain boundary and make up the deficiency of dealing with the boundary conditions in traditional SPH algorithm so that the approximation accuracy of a function can reach two order in the domain of interest.Then the second and third kinds of boundary condition of a fixed problem are handled based on the FDM algorithm, so that the calculation of complex boundary problems can be attributed to the solution of the first kind boundary problem.(2)According to the shortcomings of existing particle arrangement scheme in program preprocessing stage, a new particle arrangement scheme is proposed to compensate for the loss of accuracy in numerical calculation process when the specific problem is calculated. And it gives some references for the former processing module of the smoothed particle method in the complex computation domain.(3)Heat conduction problemls with the computation domain existing materials interfacial is solved, a series of numerical verification and comparison are carried out based on examples with analytical solution, so that SPH method is extended to solve transient heat conduction problem in soil medium. Heat transfer problem is simulated under the co-action of heat pipe and surface temperature in geotechnical medium, the temperature evolution with the time variation is obtained, and the effect of the insulator on heat conduction process is analyzed and temperature distribution characteristics with the insulator having different thermal conductivity is described.(4)SPH discrete format of the unsaturated seepage Richards equation is given, and the analysis of water flow characteristics between the particle of the domain of interest is carried out based SPH discrete format, so that mass conservation properties of Richards equation with the matrix suction head form is proved. Based on a numerical example with semi analytical solution, the feasibility of SPH algorithm for Richards equation of non saturated seepage problem is verified so as to provide a new solution for solving this kind of problem, than a evaporation problem with complex initial boundary value conditions is calculated.(5)The SPH discrete forma of the moisture-heat coupling control equations is given, then the program is written using FORTRAN language for this kind of problem and the serial program flow char of the program is given to descripe detailedly numerical implementation steps of the coupling problem. Among them, the influence of the physical parameters of materials on the evolution of physical field is analysed by numerical calculation, and temperature and volumetric water content distribution and evolution characteristics of porous media, containing cylindrical domain heat source, is calculated in different time.(6)The phase change heat conduction problems is tried to solve by smoothed particle method, an example with existing analytical solutions is carried out to validate the numerical effectiveness of the algorithm so as to realize the application of SPH method in the freezing phase change problem. The influence of the soil thermodynamic parameters on freezing front development rules is analysed in single pipe case, than the frozen wall forming process in the mine shaft construction is simulated numerically by numerical analysis.