فهرست مطالب

Scientia Iranica
Volume:27 Issue: 5, Sep Oct 2020

  • (Transactions on Mechanical Engineering (B
  • تاریخ انتشار: 1399/07/22
  • تعداد عناوین: 14
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  • Amir Shamloo *, Maryam Alsadat Rad, M.T. Ahmadian, Leyla Amirifar Pages 2343-2352
    Control of interaction between nanostructures and living cells is important for tissue engineering.The topography and hydrophilicity of nanotextured surfaces can provide information on the in vitro interactions between cells and the surrounding environment, which is of great importance in bio-applications. This study proposes a reactive ion etching (RIE) to texture the quartz surfaces with 5 and 10 nm surface roughnesses. The interaction of human cell lines (human breast cancer cells, MCF-7, and human dermal microvascular endothelial cells, HDMVEC) with the nanostructured surfaces exhibited different levels of morphogenesis when the cells adhered on the bare and nanotextured quartz surfaces. The chemical composition of the surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and results showed that cells preferred to grow on hydrophilic surfaces with hydroxyl groups.Moreover, the cellular processes, such as adhesion and spreading, were affected by the combination of physical and chemical properties of the surface, namely, surface topology and hydrophilicity. These results demonstrated the potential applications of quartz nanostructure surfaces with high microscopic image quality in tissue engineering for controlling cell growth via appropriate surface modifications.
    Keywords: quartz, Nanotextured surface, Cell, Basement membrane, Microfluidics, PDMS
  • Mehdi Bidabadi, Mohammadali Harati *, Hesam Moghadasi Pages 2353-2363

    In this work, a comprehensive mathematical method is developed to model the flame propagation through organic particles with air as a two-phase mixture, considering random distribution and particles thermal resistance. For this purpose, the structure of flame contains a preheat-vaporization zone, a reaction zone where vaporization and convection rates of particles are negligible and a post flame zone where diffusive terms are negligible in comparison of other terms zone. In order to enhance the combustion efficiency, the exhausted heat from the post flame zone is recirculated back to the preheat zone. Since this stream consists of high temperature gaseous mixture, it can enhance the temperature of the initial two-phase mixture entering the combustion chamber. The obtained results show great compatibility with the experimental findings. Apart from the randomness distribution of particles and heat recirculation phenomena, the effect of thermal resistance on the combustion properties such as flame temperature and burning velocity is studied through non-zero Biot numbers in this model. Additionally, the variation of several parameters including equivalence ratio, particle diameter and Lewis number are studied in this research.

    Keywords: Organic Dust Particle, Thermal resistance, Heat Loss, Random Combustion, Heat Recirculation
  • Hossein Nejat Pishkenari *, Farhad Ebadi Jalal Pages 2364-2371
    To realize objectives such as genome-based medicine, it is required to develop economical and fast methods for DNA sequencing at single-nucleotide resolution. In this paper a novel approach is developed to significantly improve efficiency of DNA sequencing based on physical differences between nucleotides. Here it is claimed that the reason for rather low resolution of sequencing based on physical differences, is the extremely nonlinear and complex dynamics of the DNA; it causes great dependence of DNA translocation with respect to detectors on initial conditions and environmental disturbances. In various sequencing, the position and orientation of nucleotides would thus be different in detection time. By decreasing signal-to-noise ratio, these different dynamics of nucleotides prevent detecting slight differences in physical properties of DNA bases. The correctness of this claim is verified by designing a sequencing nanodevice in which motion of a stretched single-stranded DNA (ssDNA) is constrained in such a way that axis of ssDNA backbone is fixed and in detection time each nucleotide lies in a fixed plane. Also nonlinear effects in ssDNA and detectors interactions are reduced as low as possible. Results indicate that under these constrained conditions, specific and distinct signal for each type of nucleotide will be generated.
    Keywords: DNA sequencing, nanochannel, nanotube, physical properties, molecular dynamics simulation
  • Jovan Pavlović *, Dragoslav Janosevic, Vesna Jovanović Pages 2372-2381
    The paper analyzes functional, structural and tribological parameters of kinematic pairs (joints) of the kinematic chain and manipulator drive mechanisms in hydraulic excavators. On the basis of the conducted analysis the tribological criterion is defined, as one of a number of criteria, for the optimal synthesis of manipulator drive mechanisms in hydraulic excavators. The criterion indicator is determined as a mechanical degree of efficiency of drive mechanisms, to reflect the tribological loss of power of the excavator drive system due to friction between the elements of the joints in manipulator drive mechanisms. As an example, the paper provides experimental results of tribological research and tribological criterion indicators during examination and synthesis of manipulator drive mechanisms in a hydraulic excavator of 17,000 kg in mass.
    Keywords: hydraulic excavators, drive mechanisms, optimization, tribological criterion, multybody dynamics
  • Fardin Nematzadeh *, Hossein Mostaan Pages 2382-2390
    Nowadays, Superelastic NiTi stent is used in Thoracic Aortic Aneurysm (TAA) because of its effects on minimizing such problems as low twistability, unsuitable dynamic behavior, and the shortage of radial mechanical strength. In our simulations, NiTi superelasticity is modeled based on Auricchio theory and Tanaka, Liang and Rogers theory. Auricchio Model show more consistency with the experimental data than Tanaka and Liang and Rogers Models. In the present study, a Finite Element Analysis (FEA) was used to evaluate the impacts of the applied strain on the superelastic behavior of the new geometry designed for Z-shaped TAA NiTi wire stent, for which axial strain (crushing) and radial strain (crimping) force are applied. The results showed that NiTi stent with 50% crimping and 90% crushing displayed the highest mechanical performance owing to suitable Chronic Outward Force(COF), appropriate Radial Resistive Force(RRF), complete mechanical hysteresis loop pertaining to superelastic behavior, and the lower stress and higher strain on the internal curvature of the NiTi stent. Finally, this FEM model can provide a convenient way for evaluating the biomechanical properties of TAA stents given the influences of strain applied.
    Keywords: crimping, crushing, NiTi stent, Thoracic Aortic Aneurysm (TAA), FEM
  • Siros Khorshidi *, Saeed Saber Samandari, Manouchehr Salehi Pages 2391-2408

    This paper presents free vibration of the double-curved shells and panels with piezoelectric layers in a thermal environment. Vibration characteristics of elliptical, spherical, cycloidal, and toro circular shells of revolution are studied in detail. Vibration behavior of carbon nanotubes (CNTs) reinforced composite shells embedded with piezoelectric layers at the upper and lower surfaces is scrutinized. It is supposed that temperature changes linearly through-thickness direction. Reissner- Mindlin and the first order shear deformation (FSDT) theories are implemented to derive the governing equations of the considered structures. The distribution of nanotubes is assumed to be linear along the thickness direction. For solving the equation, the General Differential Quadrature (GDQ) method is used to obtain a numerical analysis for the dynamics of the objective structures. Finally, the effects of boundary conditions, the thickness of piezoelectric layers, functional distribution of CNTs, thermal environment and kinds of the circuit (opened-circuit and closed-circuit) are analyzed. Eigenvalue system is solved to obtain natural frequencies. It is delineated that the obtained fundamental frequency by the closed -circuit is smaller than those obtained by the opened-circuit. Another interesting result is that the natural frequency is decreased by increasing temperature.

    Keywords: Vibration, Piezoelectric layer, CNT, Thermal analysis, Mindlin–Reissner theory
  • Vikas Kannojiya *, Satish Kumar Pages 2409-2418
    Particulate erosion is a major concern in slurry handling unit of a thermal power plant. The pipe bends are the most erosion affected element of a pipeline unit thus, a cost-effective method to reduce pipeline erosion is highly desirable. This work aims to suggest the optimal pipe bend design to minimize the particulate erosion by analyzing the erosion wear in geometrically different pipe bends for bottom ash slurry flow by using Computational Fluid Dynamics code FLUENT. A Three-dimensional simulation study of erosion wear is carried out by implementing Euler-Lagrange modeling along with the standard k-ε turbulence model to solve the complex multi-phase flow. Pipe bends of different bending angle (30°, 45°, 60°, and 90°), diameter (50 to 250 mm) and bending ratio (r/D = 1 to 2.5) are evaluated at different flow condition. The wear location gets shifted to the upper section of the bend and its magnitude is significantly reduced with the increase in pipe diameter and bending angle. The dynamics of multiphase slurry through different bends is analyzed to understand the complex wear phenomenon. The simulation result shows good agreement with the published findings. Finally, a least erosion affected pipe bend profile is suggested for slurry transport unit.
    Keywords: Slurry erosion, Multi-phase Flow, CFD Modeling, Bottom ash
  • Mohammad T. Shervani Tabar *, Amir Soroureddin, Habib Aminfar Pages 2419-2432

    In this paper, dynamic behavior of a vapor bubble inside a narrow channel filled with a viscous liquid has been studied numerically. The boundary integral equation method (BIEM) and the procedure of viscous correction of viscous potential flow (VCVPF) have been employed for obtaining the vapor bubble profiles during its pulsations inside the narrow channel filled with a viscous liquid. In the present paper a new method has been proposed for considering the effects of viscosity in a viscous liquid flow in the framework of the Green's integral formula together with the modified form of unsteady Bernoulli equation. The reported experimental and numerical results of the problem under investigation have been used for verification of the results of the present work. Numerical results show that, by increasing the viscosity of liquid around the vapor bubble, the bubble lifetime increases. Numerical results also indicate that for Reynolds numbers with the order of , the viscosity effects are extremely reduced. Furthermore, the dynamic behavior of the bubble in water and oil is investigated at different Reynolds numbers and at different so-called dimensionless channel radii.

    Keywords: Bubble dynamics, Boundary element method, viscous pressure correction, narrow channel, viscous potential flow
  • MohammadAmir Moharreri, Foroozan Arkian *, Kamran Lari, GholamReza Salehi Pages 2433-2442

    In this study, we present an evaluation of the (PM10) and carbon monoxide (CO) particulate matter exposure level originated from the four power plants in the area using Air Pollution Dispersion Model. Combined use of AREMOD (The American Meteorological Society/Environmental Protection Agency Regulatory Model), ArcGIS and health risk assessment were applied to estimate the level of pollution in thirteen municipal receptors in the city. The results indicated the long-range transport of the pollutants from the power plants expected to impose significant health impacts on residential receptors. Almost 80000 inhabitants of the city were exposed to PM10 concentration, ranging between 50-75 µg/m3 and 100000 were exposed to CO concentration, ranging between 40-45 µg/m3. Approximately, 1200 hectares of the city were exposed to PM10 concentration, ranging from 40 to 50 µg/m3 and 370 hectares of the city area were exposed to CO concentration between 50-75 µg/m3. Comparison between simulated and observed concentrations of pollutants shows a little overestimation by model.

    Keywords: Air dispersion model, fossil fuel power plant, PM10, CO, mashhad
  • Hamed Halimi, Farid Vakili *, Ebrahim Safari Pages 2443-2450
    This paper investigates the strength and microstructure of dissimilar weld joints between Hastelloy X, which is a nickel-based superalloy, and austenitic stainless steel 304L. Nd-YAG solid-state pulsed laser is used to perform the welding between these two alloys. Two pieces of Hastelloy X and AISI 304L sheets of 1 mm thickness, are placed edge to edge to form a butt welding configuration with each other and are welded using a pulsed laser beam with a maximum power of 400 watts. The effect of welding speed, laser power and pulse width on the strength of the joint, were investigated by changing mentioned parameters values, while the laser beam frequency and the protective gas flow rate were kept constant. Then, test samples are produced to conduct uniaxial tensile tests at room temperature. Results show that the highest-quality dissimilar joint can be found by optimizing the welding power, beam pulse width, and welding speed.
    Keywords: Hastelloy X, Stainless Steel, Laser Welding, Scan Electron Microscope
  • Tasawar Hayat, F. Masood, Sumaira Qayyum *, Muhammad Ijaz Khan Pages 2451-2464
    Soret and Dufour effects on MHD flow of Williamson fluid between two rotating disks are examined. Impacts of stratification, viscous dissipation and activation energy are also considered. Bejan number and entropy generation for stratified flow is discussed. The governing PDE's are converted into ODE's by using Von Kármán transformations. Convergent solution of complicated ODE's is found by homotopic procedure. The results of physical quantities are discussed through plots and numerical values. It is noted that axial and radial velocities are more for greater Weissenberg number. Temperature and concentration profiles are decreasing functions of thermal and solutal stratification parameters respectively. Entropy and Bejan number show the opposite trends for higher Weissenberg number and Brinkman number.
    Keywords: Williamson fluid, Rotating disks, Activation energy, viscous dissipation, entropy generation, Soret, Dufour effects, stratification
  • Z. Abbas, Jafar Hasnain *, Muhammad Aqeel, Irfan Mustafa, Abuzar Ghaffari Pages 2465-2477
    In this problem, we present a theoretical study for the slip effects on the two-dimensional flow of a nano liquid in a semi-porous channel designed by two long rectangular plates having porous media. One of the channel walls is porous and other is rigid as well as slippery. A magnetic field of homogenous strength is also applied transversely to direction of flow. Magnetic nanoparticles and non-magnetic nanoparticles are considered with ethylene glycol and water as base fluids. Least Square method and Galerkin method are adopted to solve the equations transformed from partial differential equations to ordinary ones by Berman’s similarity transformations. The obtained results from the two analytical methods are compared with the results obtained by fourth order Runge-Kutta numerical method(NM). By comparing the results of GM and LSM it is observed that variation in velocity profiles is minimal however the accuracy of GM is higher than LSM. The contributions of various flow parameters on flow field are presented through graphs. Results show a decrease in the fluid velocity with an increase in the slip parameter and porosity parameter. Flow field is less for the case of magnetic nanoparticles as compared to nonmagnetic particles for different base fluids.
    Keywords: Semi-porous channel, Nanofluid, Porous medium, slip effects, series solution
  • Hadi Fallah Ardeshir *, Biyuk Ehghaghi, Mahdi Nili Ahmadabadi Pages 2478-2488

    In this work, an inverse design algorithm called Ball-Spine (BSA) is developed as a quasi-3D method and applied to the meridional plane of a centrifugal pump impeller in an effort to improve its performance. In this method, numerical analyses of viscous flow field in the passage between two blades are coupled with BSA to modify the corresponding hub and shroud geometries. Here, full 3D Navier-Stokes equations are solved within a thin plane of flow instead of solving inviscid, quasi-3D flow equations in the meridional plane. To demonstrate the validity of the present work, the performance of a centrifugal pump is first numerically investigated, and then compared against available experimental data. Defining a target pressure distribution on the hub and shroud surfaces of the flow passage, a new impeller geometry is then obtained in accordance with the modified pressure distribution. The results indicate a good rate of convergence and desirable stability of BSA in the design of rotating flow passages. Overall, the proposed design method resulted in the following major improvements: an increase in static pressure along the streamline, 5% of increase in the pump total head and delay in the onset of flow cavitation inside the impeller.

    Keywords: Inverse design, Centrifugal Pump, Meridional plane, Quasi-3D, Impeller, Viscous
  • Muhammad Awais * Pages 2489-2497
    The problem of buildup of hydrocarbon deposits on truck engine surfaces may reduce the fuel efficiency, in addition increasing the amount of unburned fuel as exhaust gases can lead to environmental risk. This problematic issue can be resolved by applying anti-stick coatings on engine pistons using PVD technique. In this work, broad range of coating substrate systems (Chrome based (CrN, CrAlTiN), Oxides (TiOx and ZrOx), Carbon based (Graphit-iC™ and Dymon-iC™) and special coating (TiB2), are investigated to determine their ability to act as anti-stick coatings. All the coatings investigated in this study, were applied on polished parts cut from engine piston cylinders. Characterizations were performed after applying droplets of engine oil and heat treating the surfaces up to 400 °C. Based on the evaluation of oil adhesion, surface energy, coating thermal stability, surface morphology, mechanical and crystallographic properties, the anti-stick performance ranking of coatings was suggested for truck engine piston application in order to improve their performance.
    Keywords: PVD coatings, fuel efficiency, anti-stick, Thermal analysis, performance ranking