Numerical Simulation of Non-Homogeneous Viscous Debris-Flows Based on the Smoothed Particle Hydrodynamics (SPH) Method

Non-homogeneous viscous debris flows are characterized by high density, impact force and destructiveness, and the complexity of the materials they are made of. This has always made these flows challenging to simulate numerically, and to reproduce experimentally debris flow processes. In this study, the formation-movement process of non-homogeneous debris flow under three different soil configurations was simulated numerically by modifying the formulation of collision, friction, and yield stresses for the existing Smoothed Particle Hydrodynamics (SPH) method. The results obtained by applying this modification to the SPH model clearly demonstrated that the configuration where fine and coarse particles are fully mixed, with no specific layering, produces more fluctuations and instability of the debris flow. The kinetic and potential energies of the fluctuating particles calculated for each scenario have been shown to be affected by the water content by focusing on small local areas. Therefore, this study provides a better understanding and new insights regarding intermittent debris flows, and explains the impact of the water content on their formation and movement processes

Comparison of Optimization Methodologies for Sustained-Yield Groundwater Pumping Planning in East Shore Area, Utah

Combined simulation and optimization models, which are helpful for long-term groundwater planning of complex nonlinear aquifer systems, are developed using alternative modelling approaches. The models incorporate a representation of steady-state, quasi-three-dimensional head response to pumping within an optimization . An embedding model which describes exactly the nonlinear flow of an unconfined aquifer is presented. In contrast with the embedding models presented in the Utah State University Ground Water Model, it directly achieves the optimal solution without a cycling. To address the nonlinearity of the flow system, response matrix models couple superposition with the cycling procedure. Their linear influence coefficients are generated using a modified McDonald and Harbaugh model. First, these models are tested for a hypothetical, 625 cell, nonlinear aquifer system and compared in terms of computational accuracy and efficiency. All of the models achieve the same optimal solution. The fully nonlinear embedding model attains the same optimal solution regardless of how far the initial guess is from that solution. Thus, global optimality is probably obtained. A predictive program for comparing a priori the embedding and response matrix models in terms of computational size is also developed. This computes the required memory for running each model, an important factor in computational efficiency. It is based on the number of nonzero elements in the matrix of the optimization scheme. The model most appropriate for a given aquifer and desired management scenarios is dependent upon required simulation accuracy, flow conditions (steady or unsteady) , spatial scale, model computational resources requirement, and the computational capacity of available hardware and software. The linear embedding model coupled with a cycling procedure, as incorporated within a modified version of the USUGWM, is most appropriate for the subject reconnaissance level study of the East Shore Area. Here, the demand for sufficient water of adequate quality is increasing. The underlying aquifer is three-layered, unconfined/confined and is discretized into 4,880 finite-difference cells. To overcome the difficulties of solving many nonsmooth functions describing evapotranspiration, discharge from flowing wells, and drain discharge, a former cycling procedure is improved by optimizing the purely linearized models repeatedly. Using the modified version of the USUGWM, optimal sustained-yield pumping strategies are computed for alternative future scenarios in the East Shore Area

Optimal Aquifer Planning with Salt Water Boundary

Optimal sustained-yield pumping strategies were developed for the irrigated and industrialized eastern shore of the Great Salt Lake. The combined optimization and simulation model, in which steady-state, finite difference, quasi-three-dimensional ground water flow equations were embedded as constraints, computes the optima,! distribution for sustainable annual ground water pumping rates for alternative scenarios. 1. The model deals with management of a large, multilayer, confined/unconfined (linear/nonlinear) aquifer system. 2. The research can help manage water in the study area where· the demand for water of sufficient quality and quantity is increasing due to urbanization