Sharif Digital Repository

The accuracy of Reynolds Averaged Navier-Stokes (RANS) turbulence models to predict the behavior of 2-D density currents has been examined. In this work, a steady density current is simulated by the k - ε, k - ε RNG, two-layer k - ε and modified v̄2 - f model, all of which are compared with the experimental data. Density currents, with a uniform velocity and concentration, enter a channel via a sluice gate into a lighter ambient fluid and move forward down-slope. The eddy-viscosity concept cannot accurately simulate this flow because of two stress production structures found within it. Results show that all isotropic models have a weak outcome on this current, but by improving the ability of... 

The accuracy of Reynolds averaged Navier-Stokes (RANS) turbulence models to predict the behavior of two-dimensional (2-D) density current has been examined. In this work, a steady density current is simulated by the κ -ε , κ -ε RNG, two-layer κ -ε and modified v 2̄ - f models. All models are compared with available experimental data. Density current with uniform velocity and concentration enters a channel via a sluice gate into a lighter ambient fluid and moves forward down-slope. The eddy-viscosity concept cannot accurately simulate this flow because of two stress production structures in it. Results show that all isotropic models have a weak outcome for this current, but with improving the... 

The deposition behavior of fine sediment is an important phenomenon, and yet unclear to engineers concerned about reservoir sedimentation. An elliptic relaxation turbulence model (v2̄ - f model) has been used to simulate the motion of turbid density currents laden whit fine solid particles. During the last few years, the v2̄ - f turbulence model has become increasingly popular due to its ability to account for near-wall damping without use of damping functions. In addition, it has been proved that the v2̄ - f model to be superior to other RANS methods in many fluid flows where complex flow features are present. Due to low Reynolds number turbulence of turbidity current,(its critical Reynolds... 

In this paper, the structure of a wall jet deflected by a baffle along with the trajectory of particles has been studied. This baffle is used to produce a stable deflected surface jet, thereby deflecting the high-velocity supercritical stream away from the bed to the surface. An elliptic relaxation turbulence model (ν̄2-f model) has been used to simulate this submerged flow. In recent years, the ν̄2- f turbulence model has become increasingly popular due to its ability to account for near-wall damping without use of damping functions. In addition, it has been proven that the ν̄2- f model is superior to other Reynolds-averaged Navier-Stokes (RANS) methods in many flows where complex flow... 

In this paper, the structure of a wall jet deflected by a baffle along with the trajectory of particles has been studied. This baffle is used to produce a stable deflected surface jet, thereby deflecting the high-velocity supercritical stream away from the bed to the surface. An elliptic relaxation turbulence model (v2̄ - f model) has been used to simulate this submerged flow. During the last few years, the v2̄ - f turbulence model has become increasingly popular due to its ability to account for near-wall damping without use of damping functions. In addition, it has been proven that the v2̄ - f model is superior to other RANS methods in many fluid flows where complex flow features are... 

This paper introduces the concept of a submerged hydraulic jump being used for energy dissipation. A baffle wall is used to produce a stable deflected surface jet, thereby deflecting the high-velocity supercritical stream away from the bed to the surface. An elliptic relaxation turbulence model (v 2̄ - f model) has been used to simulate this submerged flow. During the last few years, the v2̄ - f turbulence model has become increasingly popular due to its ability to account for near-wall damping without use of damping functions. In addition, it has been proved that the v̄2 - f model is superior to other RANS methods in many fluid flows where complex flow features are present. In this study,... 

The learning effects of the workers and machine deterioration in an aggregate production planning (APP) problem have not been taken into account in the literature yet. These factors affect the performance of any real-world production system and require attention. In this paper, a bi-objective optimization model is developed for an APP problem with labor learning effect and machine deterioration. The first objective of this model maximizes the profit by improving learning and reducing the failure cost of the system. The second objective function minimizes the costs associated with repairs and deterioration, which depend on the failure rate of the machines in the production periods. The aim of... 

This paper proposes an integrated integer nonlinear programming model for a concurrent cell formation and production planning problem in a dynamic cell-manufacturing system (DCMS) with limited resources to setup cells and to procure machines. The proposed model seeks to minimise the total costs associated with the production planning and the cell construction and formation under a dynamic system. To validate the model, it is first converted to a linear programming. Then, a numerical example is presented based on which the branch and bound method is used to solve it employing the Lingo 8 software. Besides, due to NP-hardness of the problem, two meta-heuristic algorithms namely a GA and a PSO... 

A significant part of torsional effects in buildings is due to disregarding the arrangement of infill walls during the design. This is a challenging issue since on the one hand the structural engineers do not usually consider infill walls in modeling a structure, while on the other hand the architects do not pay attention to the seismic behavior of infill walls during architectural design. In this research, an approximate method for identifying the torsion caused by infill walls was proposed to be used at the final stages of basic architectural design, which is based on the geometric specifications of architectural plans and does not require structural specifications. For this purpose,... 

When the stiffness of a story is much less than the story above it, a significant portion of lateral displacement of the building is concentrated in this story and soft story is formed. One of the main reasons of soft story in buildings is eliminating or reducing the infill walls in lower stories. This reason is more important than the others because structural engineers usually neglect infill walls in modeling the structure, and on the other hand, architects do not consider the seismic behavior of infill walls during architectural design. In this research, based on the provision of soft story in seismic codes, 2277 macro models with different arrangements of infill walls in the adjacent... 

This paper presents an analysis of the effects and propagation of faults in the open-core 32-bit OpenRISC 1200 microprocessor. The analysis is based on a total of 13,000 transient faults injected into 65 parts of the CPU module in the OpenRISC 1200 core described at the RTL model. A comparison of the effects of faults on the various parts of the CPU including the pipeline's registers, the CPU component such as the register file, the control unit, and the ALU, and the data and address buses is done. It is shown that about 30%, 40% and 27% of injected faults terminated in address, data, and control errors respectively. About 28% of all injected faults resulted in failures. © 2008 IEEE