An object-oriented programming of an explicit dynamics code: application to impact simulation

During the last fifty years, the development of better numerical methods and more powerful computers has been a major enterprise for the scientific community. Recent advances in computational softwares have lead to the possibility of solving more physical and complex problems (coupled problems, nonlinearities, high strain and high strain rate problems, etc.). The development of object-oriented programming leads to better structured codes for the finite element method and facilitates the development, the maintainability and the expandability of such codes. This paper presents an implementation in C++ of an explicit finite element program dedicated to the simulation of impacts. We first present a brief overview of the kinematics, the conservative and constitutive laws related to large deformation inelasticity. Then we present the design and the numerical implementation of some aspects developed with an emphasis on the object-oriented programming adopted. Finally, the efficiency and accuracy of the program are investigated through some benchmark tests

Derivation of near-optimal pump schedules for water distribution by simulated annealing

The scheduling of pumps for clean water distribution is a partially discrete non-linear problem with many variables. The scheduling method described in this paper typically produces costs within 1% of a linear program-based solution, and can incorporate realistic non-linear costs that may be hard to incorporate in linear programming formulations. These costs include pump switching and maximum demand charges. A simplified model is derived from a standard hydraulic simulator. An initial schedule is produced by a descent method. Two-stage simulated annealing then produces solutions in a few minutes. Iterative recalibration ensures that the solution agrees closely with the results from a full hydraulic simulation

GPU-Accelerated Simulation of a Rotary Valve by the Discrete Element Method

The rotary valve is the most frequently used piece of equipment that is suitable for the controlled feeding or discharging of products in powdered or granular form. It is usually connected to silos, hoppers, pneumatic conveying systems, bag filters or cyclones. In this paper, a simulation study is presented on the discharge of solid particles from a silo through a rotary valve. The discrete element method (DEM), which accounts for collisions between particles and particle-wall collisions, was used to model and simulate the motion of individual particles. The diameter of the simulated silo was 0.2 m and a total of 245,000 particles were calculated. In the simulations, the effect of the geometric and operational parameters of the rotary valve on the mass outflow rate was investigated. The diameter of the rotary valve varied between 0.06 and 0.12 m and the rotational speed of the rotor was changed between 0.5 and 5 1 . The simulations showed that the mass outflow rate of the particles from the rotary valve changes periodically due to its rotary cell structure. Within the lower range of rotational speeds of the rotor, the mass outflow rate of particles changes linearly in correlation with the rotational speed. The identification of this linear section is important in terms of control as this would facilitate the implementation of control devices by applying well-established linear control algorithms. Adjacent to the linear section, the dependence of the average mass outflow rate on the rotational speed was found to be nonlinear. Within the upper range of examined rotational speeds for each diameter of the rotary valve, the mass outflow rate reaches a maximum then decreases. The simulations were performed using GPU hardware. The application of parallel programming was an essential aspect of the simulations and significantly decreased the calculation time of simulations. In the treatment of particle-wall contacts, a novel flat triangular-based geometric representation technique was used which allows the particle-wall contacts to be calculated more effectively and their treatment implemented more easily into the parallel programming code. Using the calculated particle positions, the particles were visualized to view the effect of the interactions between the particles and rotor blades on particle motion. The simulation results showed that the discrete element method is capable of determining the detailed flow patterns of particles through the rotary valve at various rotational speeds