Automatic Generation Of Irregular Sand Particle Assemble

The automatic generation of irregular sand aggregate can be used in DEM Simulation and permeability analysis of engineering geology.This thesis introduces the discrete Fourier analysis method and Thiessen polygon method,uses Fourier descriptors to generate irregular particle shapes and combines the Thiessen polygon method to generate two-dimensional irregular polygon meshes,thereby obtaining a two-dimensional planar random distribution of the set of particles.The following results have been achieved:(1)Using the Fourier spectrogram to analyze the particle shape features.Five representative shape parameters were proposed.The correspondence between these shape parameters and Fourier factors(Dn)was analyzed.The results showed that Fourier factors D2,D3 and D8 had strong correlation with these five parameters respectively,indicating that D2,D3 and D8 can better represent different levels of particle shape.(2)Based on traditional Thiessen polygon method and the reverse Monte Carlo method(RMC method),discussed how to divide polygon meshes,based on Thiessen polygon method and RMC method,the deep optimization is carried out to improve the operation efficiency obviously.Meanwhile,a series of discussions have been made on the convergence property of RMC method,the simulations found that VAR value have a greater impact on the number of RMC operations,with 0.4 being the cut-off point,different VAR values correspond to the different initial sampling points distribution.(3)The particles are filled with ODEC(Overlapping Discrete Element Cluster)method and different parameters affecting the particle filling effect were analyzed.It was found through simulation that particles with similar polygon shape could be generated by controlling the Fourier descriptor Dn and phase angle δn.Meanwhile,the results show that the maximum filling porosity is mainly controlled by D2 and D3 values.(4)Two kinds of random sets of particles with great differenceare are compared and analyzed,and on the other hand,based on four different parameters,the probability entropy,the fractal dimension,the porosity and the permeability coefficient,the difference between the scanned particle set diagram and the automatic generation of particle set diagram is compared between the two experiments.The relative errors are 1%,1.8%,1.7%and 1.8%,respectively,which are all below 2%,indicating that automatic generation of particle sets has a similar distribution with real particle collections.