Step size control for efficient discrete element simulation

The step size determines the accuracy of a discrete element simulation. The position and velocity updating calculation uses a pre-calculated table and hence the control of step size can not use the integration formulas for st ep size control. A step size control scheme for use with the table driven v elocity and position calculation uses the difference between the calculatio n result from one big step and that from two small steps. This variable tim e step size method chooses the suitable time step size for each particle at each step automatically according to the conditions. Simulation using fixed time step method is compared with that of using vari able time step method. The difference in computation time for the same accu racy using a variable step size (compared to the fixed step) depends on the particular problem. For a simple test case the times are roughly similar. However, the variable step size gives the required accuracy on the first ru n. A fixed step size may require several runs to check the simulation accur acy or a conservative step size that results in longer run times. (C) 2001 Elsevier Science Ltd. All rights reserved.