Scientia Iranica
Volume:16 Issue: 2, 2009

Abstract. This paper provides an investigation into the in uence of wake and skew on a ship propeller performance, based on the potential Boundary Element Method (BEM). Two types of in ow wake from a ship (i.e. Seiun-Maru and MS689) have been investigated for two propeller types; a Conventional Propeller (CP) and a Highly Skewed Propeller (HSP). The computed results include pressure distribution, open water characteristics and thrust uctuation for one blade and for all blades of the propeller. Calculations of the unsteady pressure distributions, thrust and torque are in good agreement with experimental data. In addition, the e ect of propeller skew angle on the performance of thrust and torque, is investigated. Keywords: Skewed propeller; In ow wake; Hydrodynamic performance.

Abstract. A fully coupled formulation of thermo- uid shape design problems has recently been developed in which the unknown nodal coordinates appear explicitly in the formulation of the problem. This \direct design" approach is, in principle, generally applicable and has been successfully applied in the context of potential and Euler ow models.This paper focuses on the direct design of ducts using the ideal ow model and may be considered as an addendum to the paper entitled \Direct Design of Ducts" [1]. However, a cell-vertex nite volume method is used and a di erent boundary condition implementation technique is applied, as compared to the method presented in the previous paper. The other new feature is that a non-linear algebraic method is used for grid generation. The method is also proved to be capable of designing complex ow passages, such as branched ducts. Keywords: Fully-coupled inverse method; Direct design; Internal ow; Stagnation point.

Abstract. One of the most important phenomena to a ect the motion behaviour of Micro Resonators is their thermal dependency. This has recently received the attention of researchers widely. A thermal phenomenon has two main e ects, the rst is damping, due to internal friction, and the second is softening, due to Young''s modulus-temperature relationship. In this research work, some theoretical and experimental reported results are used to make a proper model, including thermal phenomena. Two Lorentzian functions are used to describe the restoring and damping forces caused by thermal phenomena. In order to emphasize the thermal e ects, a nonlinear model of the MEMS, considering capacitor nonlinearity and mid-plane stretching, has been used. The responses of the system are developed by employing a multiple time scale perturbation method on a non-dimensionalized form of the equations. Frequency response, resonance frequency and peak amplitude are examined by varying the dynamic parameters of the modelled system. Finally, Fuzzy Generalized Cell Mapping (FGCM) is introduced and applied to the Micro Resonator''s dynamical system behaviour. It is then concluded as to how the model uncertainties and di erent initial conditions can a ect the working domain of the system and/or make it pull in instabilities. At the end, it can be seen that FGCM is a useful method for monitoring the working regions of Micro Resonators, while varying system parameters. Keywords: Micro resonator; Thermal e ects; Nonlinear dynamics; Fuzzy generalized cell mapping.

Abstract. In the present investigation, a hot rolling process of AA5083 aluminum alloy is simulated. The approach is based on the thermo-mechanical analysis of the problem using the Finite Element Method (FEM). The temperature distribution in the roll and the slab, the stress, strain and strain rate elds, are extracted throughout a transient analysis of the process. The main hypotheses adopted in the formulation are: The thermo-viscoplastic behavior of the material, expressed by the Perzyna constitutive equation and rolling under plane-deformation conditions. The main variables that characterize the rolling process, such as the geometry of the slab, load, rolling speed, percentage of thickness reduction, initial thickness of the slab and friction coecient, have been expressed in a parametric form, giving good exibility to the model. The congruence of the results has been evaluated using experimental and theoretical data available in the literature. Keywords: Hot rolling process; Plane strain deformation; Sequential coupling; Contact pressure; E ective stress eld; Temperature distribution.

Abstract. In this research, the e ective Hamiltonian theory is described and applied to the calculation of current-current (Q1;2) and QCD penguin (Q3;


; 6) decay rates. The channels of charm quark decay in the quark levels are: c! dud, c! dus, c! sud and c! sus where the channel c! sud is dominant. The total decay rates of the hadronic of charm quark in the e ective Hamiltonian theory are calculated. The decay rates of D meson decays according to Spectator Quark Model (SQM) are investigated for the calculation of D meson decays. It is intended to make the transition from decay rates at the quark level to D meson decay rates for two body hadronic decays, D! h1h2. By means of that, the modes of nonleptonic D! PV, D! PP, D! V V decays where V and P are light vector with JP = 0􀀀 and pseudoscalar with JP = 1􀀀 mesons are analyzed, respectively. So, the total decay rates of the hadronic of charm quark in the e ective Hamiltonian theory, according to Colour Favoured (C-F) and Colour Suppressed (C-S) are obtained. Then the amplitude of the Colour Favoured and Colour Suppressed (F-S) processes are added and their decay rates are obtained. Using the spectator model, the branching ratio of some D meson decays are derived as well. Keywords: E ective Hamilton; c quark; D meson; Spectator model; Hadronic; Colour favoured; Colour suppressed.

Abstract. In this article, a v2f model is employed to conduct a series of computations of incompressible ow in a periodic array of square cylinders simulating a porous media. A Galerkin/least-squares nite element formulation employing equal order velocity-pressure elements is used to discretize the governing equations. The Reynolds number is varied from 1000 to 84,000 and di erent values of porosities are considered in the calculations. Results are compared to the available data in the literature. The v2f model exhibits superior accuracy with respect to k􀀀" results and is closer to LES calculations. The macroscopic pressure gradients for all porosities studied showed a good agreement with Forchheimer-extended Darcy''s law in the range of large Reynolds numbers. Keywords: Porous media; Turbulent ow; Volume averaging; v2f model.

Abstract. In this paper, vibration analysis of rotating laminated composite cylindrical shells using a combination of the layerwise theory and wave propagation approach is investigated. This combination enables us to study all the conventional boundary conditions in our analysis. Results obtained have been compared with those available in the literature and a good agreement has been observed. In contrast to the Equivalent Single Layer theories (ESL), the layerwise theory is constructed on the basis of C0- continuity through the laminate thickness. For the surface of the shell, a displacement eld based on the wave propagation approach is proposed. The e ect of Coriolis and centrifugal accelerations on the circumferential and longitudinal modes is investigated. At high rotational speeds, the stationary frequency is smaller than both the forward and backward frequencies and this di erence increases with the increase of rotational speed. The in uence of boundary conditions on the frequencies is more signi cant at lower circumferential modes but at higher modes the e ect of the boundary condition is in nitesimal. Keywords: Rotating laminated cylindrical shells; Layerwise theory; Wave propagation.

Abstract. Urban transportation is one of the main sources of air pollution in mega cities, and urban job related trips can e ectively in uence the state of air quality. Tehran, the capital of Iran, with a population of 7.3 million, was selected for this study. The present model is designed to investigate the e ect on trac of the business working hours of di erent occupations and, as a result, on the status of air pollution. Daily job, non-job and recreational trips using the present vehicle eet is a major factor a ecting air pollution in Tehran. In the context of the present study, the necessary information was utilized to de ne some relations between job trips and pollutant emissions. The result showed that a proper adjustment of opening hours for di erent jobs can result in a reduction of pollutant emissions by as much as 20% during daily trac peak hours. Keywords: Mathematical model; Air pollution; Job trips; Trac control measures.

Abstract. In this research, the Homotopy-Perturbation Method (HPM) has been used for solving sine- Gordon and coupled sine-Gordon equations, which have a wide range of applications in physics. HPM deforms a dicult problem into a simple one which can be easily solved. The results obtained by HPM are then compared with those of the Adomian Decomposition Method (ADM). The method has been shown to e ectively, easily and accurately solve a large class of nonlinear problems with approximations converging rapidly to accurate solutions. Keywords: Sine-Gordon equation; Coupled sine-Gordon equation; Homotopy-perturbation method; Traveling wave solution.