Scientia Iranica
Volume:24 Issue: 1, 2017

A numerical analysis has been made on mixed convection in a lid-driven square cavity when both vertical sidewalls are partially heated and cooled in the presence of uniform magnetic field. Three parallel locations and two dissimilar locations for heating and cooling on left and right sidewalls are considered. The top and bottom walls with the remaining locations free from heating and cooling on both vertical sidewalls are considered to be adiabatic. The governing equations are solved by the finite volume method. The resulting effects on combined convection flow and heat transfer for different heating and cooling locations are exhibited graphically for the variations of the Richardson and Hartmann numbers. The average heat transfer rate enhances in the similar locations than dissimilar locations

This paper is devoted to investigate the inelastic displacement spectra compatible to Iran. Owing to inadequacy of code-compliant elastic design spectra to predict structural damage during sever earthquakes, different approaches are proposed to overcome this problem. Inelastic design spectrum is one of the most well-known methods introduced by researchers. In practice, attenuation relationships can be used in probabilistic seismic hazard analysis to obtain the inelastic design spectrum. In this paper a new ground motion prediction equation has been proposed for inelastic spectral displacement. In this regard, 806 horizontal ground motions are utilized with magnitudes ranging from 4 to 7 and epicentral distances less than 200 Km which are obtained from 330 earthquakes in Iran. According to the tectonic condition, Iran zonecan be divided into two parts: Zagrosand Alborz-central Iran. However, three equations have been presented for the whole country zone, Zagros and Alborz-central Iran zones, separately. The main parameters such as earthquake magnitude, site-source distance and site conditions have been related to the inelastic spectral displacement. Based on average shear wave velocity to a depth of 30m, sites have been categorized into three classes. For practical purpose, simplified equations have been proposed to predict inelastic spectral displacements for Iran.

This paper addresses a problem of plane elasticity theory for a doubly connected body whose external boundary is a rhombus with its diagonals lying at the coordinate axes OX and OY . The internal boundary is the required full-strength hole and the symmetric axes are the rhombus diagonals. Absolutely smooth stamps with rectilinear bases are applied to the linear parts of the boundary, and the middle points of these stamps are under the action of concentrated forces, so there are no friction forces between the stamps and the elastic body. The hole boundary is free from external load and the tangential stresses are zero along the entire boundary of the rhombus. Using the methods of complex analysis, the analytical image of Kolosov-Muskhelishvili''s complex potentials (characterising an elastic equilibrium of the body), and the equation of an unknown part of the boundary are determined under the condition that the tangential normal stress arising at it takes the constant value. Such holes are called full-strength holes. Numerical analysis are performed and the corresponding graphs are constructed.

A ordable motion sensors that are recently developed for video gaming have formed a budding line of research in the eld of physical rehabilitation. These sensors have been used in many task-based applications to analyze the patients'' status based on their completion of assigned tasks. However, as the accuracy of such sensors is lower than that of the clinical ones, their measured data has had very limited use in quantitative motion analysis to this date. The aim of this article is to determine Kinect''s ability and accuracy in calculating higher-order kinematic parameters, such as velocity and acceleration, in hand movements. Four methods, i.e. moving average, Butterworth lter, B-spline, and Kalman lter, were proposed to calculate velocity and acceleration from Kinect''s raw position data. The results were experimentally compared with two established motion capture systems, i.e. Vicon and Xsens, to analyze the strengths and weaknesses of each method. The results show that B-spline is the best method for calculating velocity and acceleration from Kinect''s position data. Using this method, these parameters can be measured with an acceptable accuracy.

In this article magnetohydrodynamics (MHD) boundary layer flow of an incompressible upper convected Maxwell fluid has been studied.The governing equations has been transform to nonlinear Ordinary differential equation (ODE) by using similarity trabsformation. The mathematical theory of Optimal Homotopy Asymptotic Method (OHAM) is presented and the results obtained by this method is compared with numerical results showing its accuracy. The effect of Hartman and Deborah numbers has been discussed.

In this study mixing of laminar non-Newtonian nanofluids in an injection micromixer was studied, numerically. The important and new feature of study is using of non-Newtonian base fluid in nanofluid.The Titanium dioxide/0.5%wt Carboxymethyl Cellulose aqueous solution was used as nanofluid. Mixture model was used for simulation of nanofluid flow inside the micromixer. The governing equations were solved by finite volume method using a FORTRAN code. Also, in this paper new modified successive over relaxation method has been introduced to decrease the computation time, considerably. The results indicated that number of injection flows and using of baffles had significant effect on mixing index. It should be noted that the distance between baffles is an important parameter in mixing.

The present paper focuses on the assessment of turbulent effects on the impact force, spray, and secondary impact force of the wedge water entry. For this purpose, a finite element based finite volume method code coupled with volume of fluid has been developed. The k-ε method has also been implemented to model the turbulence effects. The developed code is validated against experimental data with good accordance and is then used to model the water entry of wedges with deadrise angles ranging from 10 to 60 degrees at different velocities of 1 and 2 m/s with laminar and turbulent assumptions. Subsequently, the resulting forces and free surfaces are compared for three critical instances of “Peak”, “Hollow”, and “2nd impact”. It is illustrated that turbulence has negligible effects on the force and free surface in the main water entry process. However, turbulent effects rise up to 14.23% for the secondary impact forces.

In the present work the spray characteristics of bio-ethanol and its blends have been experimentally and theoretically investigated. To have a comprehensive study, the effects of ambient condition and injection pressure on the spray of different blends have been considered. Macroscopic and microscopic characteristics of spray such as tip penetration length, cone angle, projected area, volume, Sauter Mean Diameter (SMD), and Ohnesorge number are investigated precisely. Besides, air entrainment and atomization analysis have been carried out to improve mixture formation process. Using curve fitting and least squares method, theoretical correlations have been suggested in such a way to predict experimental results with the accuracy of 9.9%. To have a good estimation for the calculated parameters, uncertainty analysis has been performed. The results demonstrate enhancing the injection pressure or decreasing the ambient pressure, improve the atomization characteristics of spray. Moreover outcomes of this study indicate, spray tip penetration is enhanced by increasing the injection pressure or bio-ethanol percentage in the blend, while spray cone angle showing opposite behavior.

In this paper, a thermodynamically-consistent constitutive model recently proposed for nanocomposite shape memory polymers (SMPs) is used as a basis for development of SMP beam element in a nite element framework. The beam theory utilized here, is the Euler- Bernoulli beam theory with its basic assumptions. E ects of di erent material as well as the geometric structural parameters e.g., reinforcement (nano/micro-particles) volume fraction, viscosity coecients and external loads are studied on the thermoemchanical responseof the structure in this work. The beam element numerical results are compared to those of 3D nite element modeling, to verify the validity of the beam element formulation andthe assumptions made therein. This beam element provides us a fast and reliable tool in simulation of structures consist of reinforced SMP beams. As an application, the developed nanocomposite SMP beam element could be used for numerical modeling of thermechanical response of the drugs (e.g., theophylline) coated by lms of SMP nanocomposites. It is shown that the numerical results are in correspondence with those of experiments reported for sustained release of SMP-nanocomposite based drugs.

Gas metal arc welding (GMAW) can be considered the most extensively used process in automated welding due to its high productivity. However, to simultaneously achieve several conflicting objectives such as reducing production time, increasing product quality, full penetration, proper joint edge geometry and optimal selection of process parameters a multi criteria optimization procedure must be used. The aim of this research is to develop a multi criteria modeling and optimization procedure for GMAW process. To simultaneously predict weld bead geometry (WBG) characteristics and heat affected zone (HAZ), a back propagation neural network (BPNN) has been proposed. The experimentally derived data sets are used in training and testing of the network. Results demonstrated that the finely tuned BPNN model can closely simulate actual GMAW process with less than 1% error. Next, to simultaneously optimize process characteristics the BPNN model is inserted into a particle swarm optimization (PSO) algorithm. The proposed technique determines a set of parameters values and the work piece groove angle in such a way that a pre specified WBG is achieved while the HAZ of the weld joint is minimized. Optimal results were verified through additional experiments.

Shock Control Bump (SCB) reduces the wave drag in transonic flight. In high Mach transonic flows, the boundary layer separation downstream the bump, induced by the shock wave, results in the poor performance of the SCB. To control the boundary layer separation and to reduce the wave drag for two transonic airfoils, RAE-2822 and NACA-64A010, we investigate the application of two conventional flow control methods, i.e. suction and blowing, to be added to the SCB. An adjoint gradient based optimization algorithm is used to find the optimum shape and location of SCB. The performance of both hybrid suction/SCB (HSS) and hybrid blowing/SCB (HBS) is a function of the sucked or injected mass flow rate, and their position. A parametric study is performed to find the near optimum values of the aerodynamic coefficients and efficiency. A RANS solver is validated and used for this flow analysis. This study shows that both HSS and HBS methods considerably improve the aerodynamic efficiency (L/D), while the HBS method is more effective in control of the shock wave/boundary layer interaction. Using HSS method, the aerodynamic efficiencies of these two airfoils are increased by, respectively, 8.6% and 3.9%, respect to the airfoils with optimized bumps. For HBS configuration, improvements are respectively 13.5% and 9.0%. The best non-dimensional mass flow rate for suction is found to be around 0.003 for both airfoils, and for blowing this is about 0.0025 for RAE-2822 airfoil and about 0.002 for NACA-64A010. The best location for suction and blowing are found to be, respectively, right before and after the SCB.

In the recent years, different mathematical models are suggested for maneuvering of displacement vessels which are capable to estimate the vessel maneuver with acceptable precision. But simulation of planing craft maneuverability through mathematical model is not developed yet. In this paper a mathematical model is developed for planing craft maneuvering by including the rudder forces and moments. Different maneuvers are executed through the mathematical model such as straight-line stability, course keeping and turning circle maneuver. Simulation results were validated with the published experimental results and they are in good agreement. Finally, the influence of rudder angle on maneuverability of planing craft was studied and also the effect of aspect ratio has been investigated. The mathematical model and hydrodynamic coefficients were presented in this paper can be applied for the optimization of planing craft maneuvering and the course control purposes.

Finding the symmetries of the nonlinear fractional differential equations plays an important role in studying of fractional differential equations. In this manuscript firstly, we are interested in finding the Lie point symmetries of the time-fractional Kaup-Kupershmidt equation. After that by using the infinitesimal generators, we determine their corresponding invariant solutions.