DEM (Discrete Element Method) is a particle-based method for modeling the granular materials. SPH (Smoothed Particle Hydrodynamics) is also a particle-based method to analyze fluids using a limited number of integration points. These mesh-free methods are suitable to analyze geotechnical problems with large deformations or complicated geometries. Coupling DEM and SPH for simulating multi-phase media, resolves the need for the spatial mesh and prepares a more realistic understanding of the saturated granular materials. In this study by coupling both DEM and SPH methods, a novel DEM-SPH model was developed to simulate saturated granular media such as saturated sand. The particles were modeled using DEM and the inter-particle fluid was simulated using SPH. The fluid flow and the particle-fluid interactions were included in the model. The model was validated by comparing the numerical results to experimental data. The evolution of the fluid pressure distribution was investigated. Three phases were observed in fluid pressure distribution. After starting loading, a pressure wave appeared adjacent to the top wall that formed a “transient phase”. After finishing the transient phase, a “stable phase” of the fluid pressure distribution started, during which the pressure gradient changed gradually. There was an “instable phase” at large axial stains. The pressure gradient changed randomly in this phase. The results showed that the model could satisfactorily predict the undrained behavior of the saturated granular materials and capture the local parameters of the inter-particle fluid e.g. the local variations of the fluid pressure.

Evaluation of Solid-Fluid interaction is of high significance in all engineering fields. In this paper, the Smoothed Particle Hydrodynamics (SPH) and the Discrete Element Method (DEM) were employed to simulate solids and fluids, respectively. As for the simulation of water behavior, first, a single-phase “dam break” experiment is modeled by the SPH. In this model, variable smoothing length and an almost novel boundary method were utilized which resulted in a tremendous boost in its resemblance to the experiment. To couple these methods (SPH and DEM), three approaches were proposed and validated against a famous experimental test named “dam break with an elastic gate test”. Finally, to be sure of the correctness of these approaches, an elastic plate under a water column in the hydrostatic condition was simulated and the error was 2 percent in comparison with the analytical solution. In pursuit of having short run-times, parallel computing on GPU (CUDA) was employed, and a robust nearest neighbor search (NNS) algorithm was modified and developed.

Considering ongoing developments in Photogrammetry and Remote Sensing and attending to their applications such as digital true orthophoto generation from high resolution images, have already proven the urgency and necessity of approaches for generating DEM as input of these applications. In this research we describe a novel method for automatic DEM generation. We describe “Semi-Global Matching” algorithm then implement and test it for generating an initial disparity image from high resolution stereo satellite images. Furthermore, post-processing steps for removing outliers, recovering from specific problems of structured environments and the interpolation of gaps are needed, to generate an accurate disparity map. With generating a clear disparity map we can generate 3d point clouds. Then these point clouds are used for generating a precise DEM for other applications.

A deeper understanding of the milling operation of ball mills helps mineral processing engineers to control and optimize them, and therefore, reduce their consuming power. In this work, the milling operation of ball mills is investigated using two methods, i. e. DEM and combined DEM-SPH. First, a pilot scale ball mill with no lifter is simulated by both methods. Then another pilot scale ball mill with eight rectangle lifters is simulated again by both methods. The effects of lifters on ball shoulder and toe points as well as on creation of cascading and cataracting movements for balls are studied by both methods. At the present time, there is not enough measured data available for dense slurries interacting with the coarse particulates available in the public domain that can be used adequately to validate these types of predictions. The results obtained indicated that fluid slurry in the mill lowered the charge shoulder by about 28 cm and 25 cm in the no-lifter and eight-lifter cases, respectively. However, it raised the charge toe by about 36 cm and 6 cm in the no-lifter and eight-lifter cases, respectively.

This study was carried out in the western catchment of the Behzisty Township in Gorgan, Golestan province in order to develop the regression models of soil moisture. In this study, the desired measurements were made in 18 locations using TDR during 6 running days after a relatively intense rainfall event at different depths of soil. The digital elevation model was prepared from Ultra Cam images taken in 2014 with the pixel size of 1×1 m in order to estimate the terrain properties. Finally, the regression model was developed with respect to these characteristics and soil moisture. The results showed that important terrain characteristics which are greatly associated with soil moisture are horizontal curvature, slope, aspect and wetness index in the regression model. These results suggest that the diversion of material flow has controlled the amount of water in the soil, slope aspect and soil moisture. The results showed that the developed regression models can forecast at least 44 to 60% of the total variations of soil moisture in the watershed scale.

Sand production imposes a considerable cost on the oil industry. In the current study, this phenomenon is studied numerically to better understand the particulate mechanism of sanding in unconsolidated sandstones and study the effect of confining stress and pressure drawdown on sand production. The discrete element method (DEM) is used to simulate the particulate media, and the lattice-Boltzmann method (LBM) is adopted to model the fluid flow through it. The two methods are coupled, and the fluid-solid interaction is modeled using the immersed moving boundary (IMB) method. An in-house computer program is developed based on these methods to simulate the 2D sanding procedure under radial fluid flow and isotropic stress in the absence of particle cementation. The results show that the number of produced particles and the sanding rate increase with the increase of confining stress. Also, after the sand initiation, the sanding rate in all models decreases due to the formation of sand arches around the model’s inner cavity. These arches are prone to instability, and new larger arches replace them after their collapse. After examining the effect of fluid pressure difference on sand production, it is concluded that the pressure difference has little influence on sand production at relatively low-stress levels. However, at higher stress levels, the pressure difference has a considerable impact on sanding results as it increases the number of produced particles more than twice with a 50% increase in pressure difference. This study confirms that the 2D coupled DEM-LBM model can properly capture the mechanism of the sand production phenomenon.