Numerical Simulation Of Silo Discharging Process And GPU Acceleration Based On Material Point Method

Silos are widely applied in the industry fields including chemical and grain.In the discharging process of storage materials stored in silos,the internal load caused by the collision between storage materials and silo walls and storage materials seriously affects the service life of silos.It is of great significance to predict the dynamic lateral pressure of silo wall and the flow pattern of storage material during the discharging process by numerical simulation.Discrete element method has some shortcomings such as time-consuming and difficult to converge when it is used to study the discharging process of silos.The finite element method can solve the convergence problem,but the large deformation of the storage flow during the discharging process often results in the distortion of the finite element mesh.Material point method can effectively avoid mesh distortion in FEM simulation of silo discharging process by carrying material information with particles and constructing uniform background mesh at each time step.In this paper,the discharging process based on the material point method is simulated.The regularity of the discharging process is researched.And the GPU acceleration on the discharging process of silos is studied to decrease the cost of the large amount of calculation.The silo discharging process is simulated based on material point method.The calculation program of material point method for silo discharging process is written by FORTRAN language.The static balance process of silo and the discharging process of center single discharge outlet are simulated.And the static and dynamic lateral pressure of silo wall are obtained,which are in good agreement with the theoretical and finite element results.It shows that the material point method is feasible to simulate the discharging process of silos,and it also provides a new research method for the discharging of silos.The influence of technological conditions on the discharging process of silos was studied.Firstly,the influence of the quantity and opening position of the discharging outlet on the discharging process of the silo is analyzed.The flow pattern and velocities of the storage materials and the dynamic lateral pressure of the silo wall are obtained when storage materials are discharged centrally and eccentrically with the single discharge outlet,the double discharge outlet and the multi-discharge outlets.Then the effects of eccentricity,discharge outlets size,silo height-diameter ratio,friction conditions and material parameters on the dynamic lateral pressure distribution of silo wall are analyzed.The results show that the eccentric discharging with single and double discharging outlets is beneficial to the discharging of storage materials in the early and middle stages of discharging,but eccentric flow will occur,which results in the downward trend and oscillation amplitude of the dynamic lateral pressure on the wall near the discharging outlets,and the eccentric load caused is not conducive to the stability of the silo structure.The maximum dynamic lateral pressure of silos with different height-diameter ratios occurs at the lower part of the silo.The increase of Poisson’s ratio,density,modulus of elasticity and expansion angle in material parameters will lead to the increase of dynamic lateral pressure,while the increase of internal friction angle is opposite.Three parameters,friction coefficient,discharge outlet diameter and eccentricity,are selected for orthogonal test analysis.The orthogonal experiment is carried out by using numerical simulation.Range analysis shows that the combination of discharge outlet diameter with 4m,eccentricity with 0.2 and friction coefficient with 0.2 affects mostly the dynamic lateral pressure.Variance analysis show that the relationship to the significance level of three factor is The friction coefficient is bigger than the diameter of discharge outlet and bigger than the eccentricity.GPU acceleration algorithm of material points in silo discharging process is studied based on CUDA.The static balance process of silo and the discharging process of center single discharge outlet are simulated by GPU parallel acceleration program.The static and dynamic lateral pressures of silo wall are in good agreement with the simulation results of CPU,which verifies the validity of GPU acceleration program.The influence of particle number and node number on GPU acceleration algorithm during discharging process of simulated silo is studied.The results show that GPU acceleration algorithm can improve the efficiency of material point method in simulating silo discharging process,and its acceleration ratio is between 4 and 8 times.