Abstract
Wavelet transforms are used to explore the dynamic evolution of granular material by post-processing data from DEM simulations. Data sets generated from two different physical scenarios were analysed: particles in vibration cells and samples under compression. It is shown how the wavelet multiresolution analysis (MRA) helps to reveal the particle motions within a vibration box subject to applied vibrations. Two combinations of amplitude and frequency vibration were applied in this work: low frequency with high amplitude and high frequency with low amplitude. Both cases give the same acceleration amplitude of approximately 7.8g where g is the acceleration due to gravity and both mono-sized particles and binary mixture were considered. The root mean square of the fluctuating velocity and the packing fraction of the two data sets are also consistent with the analysis results of the wavelets technique. Furthermore, it is shown how the MRA techniques were used to capture the position of inhomogeneities in granular material response by analysis of data sets from simulations of biaxial and triaxial compression tests. In the case of biaxial compression, results from the wavelet analysis are compared with plots of the cumulative rotation of the particles. In the triaxial compression test where a bonded material is considered the wavelet analysis is compared with plots of the position of broken bonds in the sample. Moreover, it is shown that the MRA techniques can aid in finding the time/strain scales on which significant events occur. This information could be used to determine how frequently to output data on stress, strain-rate (velocity) and packing voidage distributions during compression, shear and flow of the granular bulk. Furthermore, the wavelet technique should be considered for applications involving quantitative analysis of experimental data generated by the other advanced experimental techniques such as photo-elasticity and X-ray computed tomography techniques.