Sharif Digital Repository

A special type of shell structure - a concrete shallow funicular shell of circular plan - is considered in this paper. Funicular shells carry their dead weight only by in-plane compression forces. Numerical analysis of funicular shells was performed using the non-linear finite-element method, considering both geometric and material non-linearities. A circular-plan concrete funicular shell unit was also constructed and its ultimate central concentrated load is determined. The ultimate load of the shell unit predicted by the numerical model was very close to the experimentally determined ultimate load, thus confirming the validity of the numerical model. The numerical results revealed the... 

The present study focuses on the simulation of two dimensional unsteady cavitating flows. For simulation of unsteady behaviors of cavitation which have practical applications, the development of unsteady PISO algorithm based on the non-conservative approach is utilized. For multi-phase simulation, single-fluid Navier-Stokes equations, along with the volume fraction transport equation, are employed. The bubble dynamics model is utilized to simulate phase change between vapor and liquid phases of the water. Unsteady simulation of cavitation around NACA66(MOD) and supercavitation around a flat plate normal to flow direction are performed to clarify accuracy of presented model. Numerical results... 

This paper considers a realistic multi-service system design problem in which each service type is a stochastic sequence of services provided by different units of facilities where each facility is modeled as a set of open Jackson queueing networks. The problem is first formulated as a mixed-integer nonlinear programming model, which is further simplified to a model with a smaller number of constraints. Three exact solution methods are applied to solve the amended model. The first one is a cutting-plane method, which is based on a piecewise-linear approximation. The second is based on a mixed-integer linear programming formulation, which is enhanced by valid inequalities. The third is to use... 

Thermal cracking is the prevalent type of distress experienced by asphalt pavements in cold regions. It is widely assumed that when thermal stresses induced in the pavement exceed the tensile strength of the asphalt surface layer, cracking occurs; however, the role of thermal fatigue should not be ignored. To better describe the low-temperature (LT) performance properties of modified asphalt binders, a new parameter, normalised tensile stress (NTS), was defined in this research. NTS values were compared with bending beam rheometer (BBR), direct tension (DT) and semi-circular bending (SCB) fracture test results. The m-value parameter of the BBR test specifies the type of asphalt binder. This... 

The present study focuses on the implementation of PISO algorithm to simulate cavitating flows. For simulation of unsteady behaviors of cavitation which have practical applications, the development of unsteady PISO algorithm based on the non-conservative approach is investigated. The effects of mixture compressibility are considered to improve accuracy of simulations. For multi-phase simulation, single-fluid Navier-Stokes equations, along with the volume fraction transport equation, are employed. The bubble dynamics model is utilized to simulate phase change. To prove capabilities of the developed PISO algorithm to simulate cavitating flows, unsteady simulation of cavitation around NACA0015... 

Thermal cracking is the prevalent type of distress experienced by asphalt pavements in cold regions. It is widely assumed that when thermal stresses induced in the pavement exceed the tensile strength of the asphalt surface layer, cracking occurs; however, the role of thermal fatigue should not be ignored. To better describe the low-temperature (LT) performance properties of modified asphalt binders, a new parameter, normalised tensile stress (NTS), was defined in this research. NTS values were compared with bending beam rheometer (BBR), direct tension (DT) and semi-circular bending (SCB) fracture test results. The m-value parameter of the BBR test specifies the type of asphalt binder. This... 

General purpose software is developed to simulate 6-DoF fluid-structure interaction in two-phase viscous flow. It is a VoF-fractional step solver based on the finite-volume discretization which uses a boundary-fitted body-attached hexahedral grid as the motion simulation strategy. As an application, a high-speed planing catamaran is simulated in steady forward motion as well as in turning maneuver. Results are compared with the available data and good qualitative and quantitative agreements are achieved. Numerical schemes and the solution algorithm of the software are consistent and show a good capability to model highly nonlinear ship motions. It can be further developed to represent a more... 

Purpose - This study aims to present compatible computational fluid dynamics procedure for calculation of incompressible three-dimensional time-dependent flow with complicated free surface deformation. A computer software is developed and validated using a variety of academic test cases. Design/methodology/approach - Two fluids are modeled as a single continuum with a fluid property jump at the interface by solving a scalar transport equation for volume fraction. In conjunction, the conservation equations for mass and momentum are solved using fractional step method. Here, a finite volume discretisation and colocated arrangement are used. Findings - The developed code results in accurate... 

Phase separation is one of the common methods for fabrication of polymeric membrane, which classifies into the categories of Thermally Induced Phase Separation (TIPS) and Nonsolvent Induced Phase Separation (NIPS), i.e. heat and mass transfer induced phase separation, respectively. NIPS has been applied more commonly than TIPS, but the membranes which have resulted from this technique have macro finger-like voids, weak mechanical strength and not high separation ability in comparison with the TIPS. In contrast, membranes produced by the TIPS method have micro scale pores, high mechanical strength and also high separation capability, however, polymeric solutions prepared at high temperatures... 

One of the underlying factors in the conservation and development of urban green spaces is the available water resources use for green areas in each region. The primary purpose of this study is to introduce the integration of a proper simulation method for runoff along with AHP-PROMETHEE decision-making method for water resources management in urban basins. The application of this approach was investigated in the city Buin Zahra of Qazvin Province of Iran. In the first step by using the analytic hierarchy process (AHP), the available water resources in the case study were weighted. In the second step, the water resources of the municipal and residential wells and water collected by... 

One of the underlying factors in the conservation and development of urban green spaces is the available water resources use for green areas in each region. The primary purpose of this study is to introduce the integration of a proper simulation method for runoff along with AHP-PROMETHEE decision-making method for water resources management in urban basins. The application of this approach was investigated in the city Buin Zahra of Qazvin Province of Iran. In the first step by using the analytic hierarchy process (AHP), the available water resources in the case study were weighted. In the second step, the water resources of the municipal and residential wells and water collected by... 

One of the most important capabilities expected from an autonomous vehicle is avoiding collision with obstacles in its path. For this purpose, autonomous vehicle must be able to perform an emergency maneuver as soon as the obstacle is detected. This paper presents a method for designing and performing an emergency maneuver in order to avoid collision with a fixed or moving obstacle in the path. A sinusoidal or exponential trajectory, which is a function of the relative distance between vehicle and obstacle, is designed as the desired trajectory for lateral motion of the vehicle. A sliding mode controller is designed in order to guarantee that the vehicle tracks that desired trajectory. The...