INTERNATIONAL JOURNAL OF INDUSTRIAL ENGINEERING AND PRODUCTION MANAGEMENT (IJIE) (INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE) (PERSIAN)
Year:2008 | Volume:19 | Issue:3|Papers Count:11

In this paper pulsatile laminar blood flow in an axisymmetric stenosed tube is simulated by the Non-Newtonian Power law model. Effect of stenosis, for severe condition of 75% reduction of local area was considered and the flow patterns for three Womersley numbers were studied. The results show that there is a fundamental difference in the flow pattern at Wo=12.5. This difference is related to second co-rotating vortex which is observed downstream of stenosis at Wo=12.5. The propagation of disturbance that leads to formation of this vortex is shown by wall shear stress surface at Wo=12.5. Examining three flow patterns shows that the time that primary vortex forms on the distal face of stenosis is delayed with increasing Womersley number.

An exact study on temperature field in a hollow cylinder of finite length which is influenced by a surrounding with harmonic boundary condition is presented. To simulate an idealized situation, it is supposed that the cylinder is homogeneous and isotropic with physical properties independent of temperature and time. Here we impose a harmonic boundary condition on the external surface of the finite cylinder using Fourier analysis. The classical method of separation of variables and Duhamel’s theory is used to calculate the temperature field under periodic boundary condition. Numerical results reve the key effects of frequency of the surrounding temperature, Biot number and shell thickness on the amplitude ratio and phase difference of the cylinder temperature. The presented solution can lead to a better understanding of temperature behavior under harmonic boundary conditions. A limited case is considered and fair agreement with an available solution is obtained.

Active control vibrations of an arbitrary point of a simply supported rectangular plate is presented in this paper. The governing differential equation of plate with attached piezoelectric sensor/actuator patches, whose effects of mass and stiffness are included by the local functions, is solved at first. The response of the plate is computed using the first nine natural modes. Then, piezoelectric patches are attached about the point based on a special arrangement and possibility of vibration reduction of the local area of the plate without reducing the global vibration of the plate is discussed. Numerical examples with four and nine patches are discussed to contrast the present method. The results show the superiority of the present approach.

The extended finite element method (X-FEM) is a numerical method for modeling discontinuties, such as cracks, within the standard finite element framework. In X-FEM, special functions are added to the finite element approximation. For crack modeling in linear elasticity, appropriate functions are used for modeling discontinuties along the crack length and simulating the singularity in the crack tip element. As a result, the degrees of freedom (D.O.F.) for the nodes arround the crack tip and the crack length are increased, the so-called node-enrichment scheme. This virtual crack modeling, which is mesh independent, avoids the usage of refined mesh and singular elements arround the crack tip, and does not require remeshing during crack growth simulation. In this paper the principles of the X-FEM are described. A new method, based on the local orthogonal coordinate system, is proposed for the node-enrichment scheme. The development of a special-purpose computer code for modeling 2D cracks using the X-FEM and the new method is presented. The code and the new method are verified through the analyses of different standard cracked geometries.

One of the ways, to control of the drag forces applying to the circular cylinder in the air flow, is control of the generated boundary layer around the cylinder, and one of the new and effective ways for control of the boundary layer, is using high voltage electrostatic field in fluid flow. In these conditions, because of the coupled relations between electric field and momentum equations, the problem is complicated and discussed as electro-hydro-dynamic or EHD. For this purpose, the equation of conservation and momentum for flow field and conservation for electric density and Poisson's for electric field are solved with numerical and finite element method. In this research we used two wire and two plate electrode for generation electric field. By use of the results, we observed that the effect of electric field on fluid flow field is widely dependent on geometry of the electrodes and the intensity of the electric field. But in fact, by applying these forces, particles momentum and the velocity of them is increased. It was shown that increasing in Reynolds number, decrease these effects.

In this paper, a new method for fracture analysis of notched cylindrical cases under explosive loading of High Explosive internal charge has been presented to determine fracture time, fracture radius, fragment velocity and acceleration. Also the fracture dynamics has been simulated by explicit and nonlinear LS-DYNA code. In numerical simulation the behaviour of metallic case has been modeled by JOHNSON-COOK model, and of HE charge by HIGH-EXPLOSIVE-BURN. Mie-Gruneisen and JWL equations of state have been used for the materials. Finally, the results of the analytical model, the numerical simulation and extended Taylor's model have been compared, and the effects of some paremeters on the fracture time, fragment velocity, and expansion radius have been discussed.

The results of an experimental study of the combustion of aluminum particles in N2/O2 gas mixtures are presented and interpreted. This research focuses on measurement of flame speed and combustion velocity in aluminum particle dust cloud combustion. The dust dispersion technique uses an annular high-speed jet which disperses dust continuously supplied via a pistontype dust feeding system. Particles of one initial diameters of 18 micron were studied in this experiment. Flame speed as a function of dust concentration was determined during the laminar stage of flame propagation in dust-oxygen-nitrogen mixtures. It was found that increasing in O2 part (21% O2 to 25% O2) in N2/O2 gas mixtures leads to increasing in combustion velocity.

Head injuries resulting from motor vehicle crashes are a leading cause of death. Injuries to head are directly related to impactor behavior, so deformable bodies can significantly reduce the severity of head injury during impact. Nowadays the soft materials named deformable materials are widely applied in industry for the sake of their energy absorbing potential, that’s why foaming materials such as polymeric and metal foams are extensively used in automobile industries to satisfy occupant protection and comfort.This study demonstrates the association between generated stresses on head and the barriers behavior. It investigates the effect of materials for their impact absorbing qualities and their behavior under impact by using LS-DYNA finite element codes. It focuses on the investigation of suitable materials for the car interior structure by analyzing their impact absorbing properties. This biomechanical study was performed by applying a visco-elastic head model for the 50th percentile male which collides with a constant velocity of 6.5 m/sec (15mph) to a barrier at the sagittal plane in the situation of frontal impact. Aluminum, ABS, Alulight, Alporas and Expanded PolyPropylene (EPP31) which are used in car industry have been selected to perform the analysis. Results shows that the maximum stress, maximum strain and peak head deceleration are directly related to material density, yielding strength and elasticity. Alporas foam with the lowest yielding strength exerts minimum stress (2.3Mpa), strain (0.000134) and also minimum peak deceleration (299g) to head while Aluminum with the maximal yield strength and density provides the highest values (60times based on stress). According to related safety standards, the exerted values due to Alporas are in a safe range and point out the energy absorbing capability of Alporas in contrast to other selected materials while Alulight, EPP31 and ABS are in the next ratings, respectively.

The purpose of this study is to present a 2-D numerical model that solves the transient equations of flow, energy and species conservation in a single tubular solid oxide fuel cell (SOFC). Also an electrical model is considered to compute the electrical potential and current distribution in the cell. Using this comprehensive model the cell dynamic operation and response in a step load current change is studied. The simulation starts when the cell is at the steady state in a specific output load. When the load step takes place, the solution continues to a secondary steady state condition. Then the cell transient behavior is analyzed. The results show that when the load current is stepped up, the output voltage reduces to steady state in about 750s.

The quality of spray depends on flow properties, ambient conditions and the kind of atomizer. This study shows how geometric parameters of swirl injector and pressure influence size, velocity and distributions of droplets. The spray characterization are measured by using phase Doppler anemometer systems. The aim of this study is the information progression and use in design injector by software codes. By this way, we obtain optimum dimensional of injectors.