In the current research, laminar flow and heat transfer of viscoelastic fluid in an axisymmetric sudden expansion with expansion ratio of 1: 3 is investigated. Finite volume method and PISO algorithm are used for numerical simulation of flow and heat transfer of viscoelastic fluid. Also, to study the effect of elasticity property of polymeric fluid flow, nonlinear Phan-Thein-Tanner (PTT) rheological model is used. Most of the researches that have been done in this field are focused on investigating hydrodynamic parameters of flow, like studies on the effect of Reynolds number and elasticity property on vortice length, so due to the scarcity of comprehensive study about the heat transfer of viscoelastic fluid flow in sudden expansion, performing the present study seems necessary. Considering some of the rheological and thermodynamic properties of viscoelastic fluid as a function of temperature is the other innovation of the current study which, due to the sensitivity of some of the viscoelastic properties to temperature, considering this hypothesis for solving energy equation is necessary. The results of numerical simulation show that the maximum quantity of local Nusselt of sudden expansion for downstream wall is approximately where vortices finish and the procedure of velocity variation is similar to a smooth pipe. Also, with increasing Reynolds number that led to enhancing length and intensity of vortices, the maximum local Nusselt in sudden expansion region moves further toward downstream.

A simple new closed form of the Green function for axisymmetric magnetostatic problems is found analytically in cylindrical coordinates. The result is verified by applying several examples.  

Aerospoke nozzle is one kind of the converging-diverging nozzle that are more effective than of the Bell nozzle. The aerospike nozzle have high efficiency in the all Number of Pressure Ratio (NPR). Also, the usability as a vector thrust is the other benefits of the aerospike nozzle. The disadvantage of the aerospike nozzle it’ s heavier than as the Bell nozzle and the aerospike nozzle requires cooling system. There are afew studies about the aerospike nozzles and the use of this type of nozzles requires more experimental and theoretical studies. In this study reported the results of numerical simulation an axisymmetric aerospike nozzle. In This study used a structure grid and the K-ε turbulence model. The effected of NPR was investigated and the NPR varied between 2 to 50. The results show linear relation between NPR and nozzle mass flow rate. In the last part of this study the effected of the spike length was studied. The four defferent spikes was modeled by 20, 40, 60 and 80 percent length of the first spike length in 10 NPR and results show the cutting more than 40 percent length of the spike effect in flow quality.

In this research, optimization process of axisymmetric extrusion dies is proposed. Plastic zone is analyzed using finite element method in the Eulerian system with flow formulation. The die profiles are defined by Bezier curves with six control points. Two effective functions are considered in this research, standard deviation of the strain rate and the rate of energy consumption during extrusion process. A coupled numerical approach of finite element analysis in Eulerian system and the non-gradient Nelder-Mead method is utilized to determine optimum die profiles. Results show that optimized die has higher uniformity in strain rate distribution and less strain values with respect to the non-optimum conical die. In the case of minimizing energy consumption rate, results show that for the die with constant and variable lengths and low friction, the die profile tends to the stream line. In die with variable length and high friction, friction has more effective role in optimization and the die length tends towards lower lengths during optimization.

In recent years, Shape Memory Alloys have found a lot of interest among researchers and engineers. Material properties of SMA's change with temperature and stress. Also due to large strains that may occure in them, geometrical nonlinearities encountered in the analysis of SMA structures. These material and geometrical nonlinearities make difficulties in the analysis of SMA structures. In this thesis a numerical model based on the differential quadrature’s method (DQM) is presented for the buckling analysis of circular cylindrical shells made of SMA material.

One of the important issues in the production of concrete is environmental variability that affects the concrete and elements constructed from this material. Due to the importance of different characteristics of concrete in short- and long-term conditions, this article aims to investigate the influence of initial temperature conditions of self-compacting concrete on its long-term characteristics and determine the initial optimal temperature of concrete. For these purposes, several experiments under three temperature conditions of 5, 20, and 40 degree-of-Celsius were conducted to evaluate the rheology and mechanical properties of fresh concrete in the range of 7 and 28 days. In these experiments, alternative mineral admixtures of cement such as micro-silica, fly ash, and zeolite were used to build the concrete specimens. Results demonstrate that the mechanical properties of the specimens increase with increasing initial temperature in the short term, while such properties significantly decrease in the long term compared to the specimens constructed under lower initial temperature. Moreover, the fluidity of self-compacting concrete increases with increasing initial temperature.

Global environmental concerns have put lightening of structures on the fore front of research in transportation industry. Among other light weight alloys, the transportation industry is considering magnesium intensive light body-in-white structure in automotive applications. Although the research in modeling technique areas is very active, a suitable practical model mimicking the severe asymmetry and anisotropy of magnesium is lacking. Loading-unloading behavior of wrought magnesium alloy over a wide range of strain has been obtained experimentally and subsequently presented here. It is shown that while the material behaves elastically isotropic, it shows a different yield in tension and compression with a high Bauschinger effect. This is attributed to the magnesium multiple deformation mechanisms of slip, extension/contraction twinning, and de-twinning resulting in an asymmetric yield and a directional dependent performance. Up-to-date there is no plasticity model commercially available that can capture this behavior.Therefore, it is necessary to develop a simple and efficient model that can serve as a benchmark tool for plasticity model evaluation. Such model is presented in this paper. The axisymmetric elastic-plastic model of Jahed and Dubey (1997) has been extended to wrought magnesium alloys. An asymmetric yield function is adopted and the obtained behavior in loading and unloading is directly incorporated in the solution process. It is shown that results are significantly different from isotropic assumptions.