Iranian Journal of Mechanical Engineering Transactions of the ISME
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Iranian Journal of Mechanical Engineering Transactions of the ISMEendaily1Thu, 01 Sep 2022 00:00:00 +0430Thu, 01 Sep 2022 00:00:00 +0430Experimental Investigation of the Flow Structure around a Pitching Airfoil by Mean and Instantaneous Data
https://jmee.isme.ir/article_253260.html
This paper focuses on a selected set of results from extensive experimental tests to characterize the wake aerodynamics of an SD7062 wind turbine airfoil in steady-state and pitch oscillating motion. Investigating the wake of an airfoil provides outstanding information on physical aspects of the downstream. Wake measurements were accomplished through hot-wire anemometers in the Laboratory of Aerodynamics at the Hakim Sabzevari University. The impact of AoA and Reynolds number were both examined in the steady-state. Regarding the pitching airfoil motion, the effect of reduced frequency, Reynolds number, symmetric, and asymmetric oscillation were also investigated. The results revealed that in both the pitching and the steady-state cases, strength of the vortices is highly related to the airfoil shape, amplitude, and Reynolds number. In respect of pitching state, the TI value is decreased as the Reynolds number increases, while it grows up with increasing the reduced frequency. Besides, TI in asymmetry oscillation is significantly higher than in symmetric oscillation, which is probably due to the formation of larger vortices. For steady-state, the instantaneous TI and velocity are almost the same as their mean values. Hence, statistical data could be used to calculate aerodynamic forces on a static airfoil. It is necessary to meticulously consider the effect of mean and instantaneous forces in the pitching state, as the forces acting on the pitching airfoil could reach several times its average state in some moments during its impact. As a result, the importance of these instantaneous loads is required to be considered enabling us to select the proper material for the airfoil.Ionic Channel Blockage Effect on the Electromechanical Model of Human Gastric Wall Smooth Muscle Cells
https://jmee.isme.ir/article_255131.html
In this paper, a three-dimensional electromechanical model is presented to investigate the effect of calcium and potassium ionic channels on the contractile behavior of human gastric wall smooth muscle cells with the finite element approach. In this model, simultaneous electrical and mechanical interactions of 240-cells and 548-links were considered. Electrophysiological interactions of cells through ion channels with the extrascellular environment and gap junctions with adjacent cells lead to the production and propagation of slow waves in smooth muscle. This wave causes contraction and peristaltic movements in the muscles of the gastric wall. By blocking calcium and potassium ionic channels by pharmacological agents can be improved disorders caused by these movements and contractions and brought them closer to the physiological state.Effect of Selecting the Suitable Design on Production Costs of Pressure Vessels
https://jmee.isme.ir/article_255132.html
In addition to standard design and production, its economics is also vital. Design and production organizations must pay special attention to the design process's cost category, selecting materials and determining production methods continually. Flexibility, access to data and information from multiple materials and the possibility of examining production methods based on the material and dimensions designed are the features of this research's results. Identifying and selecting suitable and accessible materials can be helpful in design dimensions using pressure vessel design formulas. The design and its outputs can significantly affect the weight and price of materials, production method and cost. The actual design, effects of permitted structures on material and production cost and the final total cost of a pressure vessel have been studied. The total cost values were compared and validated with target values compared with past research results. This method can be used as a general cost-based method for selecting suitable designs to identify and produce other products considering strengths, reliability and safety factors. Numerical Study of Flow Field in New Design Cyclones with Different Vortex Finder Shapes
https://jmee.isme.ir/article_696906.html
In this paper, the effect of vortex finder shape on the performance and flow field of the new design cyclones is numerically investigated using CFD techniques. Nine different geometries of vortex finder are studied in three categories each with three geometries. In the first category, the effect of vortex finder flattening is investigated. In the second category, vortex finders with three different cross section geometries circular, square and triangular are investigated. Finally, in the third category, circular vortex finders with three different diameters are modeled. The new design cyclone is based on the idea of improving cyclone collection efficiency and pressure drop by increasing the vortex length. The Eulerian-Lagrangian computational procedure is used to predict particles tracking in the cyclones. The velocity fluctuations are simulated using the Discrete Random Walk (DRW). The results show that in the flat category, vortex finder without flattening (circular cross section) possess the maximum efficiency and the lowest pressure drop and with flattening, the cyclone efficiency dramatically decreases while pressure drop remarkably increases. Among the vortex finder with different cross section, maximum efficiency is associated to the circular vortex finder while the lowest pressure drop is assigned to the triangle one. A New Modified Harmony Search Optimization Algorithm for Evaluating Airfoil Shape Parameterization Methods and Aerodynamic Optimization
https://jmee.isme.ir/article_255119.html
In this work, a modification has been made to increase the efficiency and convergence of the harmony search algorithm. Then, the capability of this amendment was investigated by applying it to the following aerodynamic problems for the first time. First, the methods of airfoil shape parametrization (Bezier curves, Parsec method, and NACA 4-digit airfoil) were investigated using an inverse optimization design by the present modified harmony search optimization algorithm. Then, inverse and direct optimization of an airfoil were carried out by the modified algorithm. Aerodynamic analysis of the problem was obtained using compressible Reynolds-Averaged Navier-Stokes (RANS) equations along with the Spalart-Allmaras turbulence model. Results showed that the Bezier curves and the Parsec method have higher flexibility than the NACA 4-digit airfoil. The Parsec method was introduced as the best approach, because of fewer control parameters. The inverse optimization results showed that the present airfoil shape optimization set can obtain the target shape with high accuracy. The Direct optimization with a maximum lift to drag ratio target function revealed that the shock waves significantly weaken at the optimum airfoil. Generally, the results obtained verify that using the modified harmony search algorithm together with the Parsec method provides a powerful tool for direct and inverse aerodynamic optimization.Stability analysis of an axially moving thin wall conical shells made of shape memory alloy
https://jmee.isme.ir/article_253843.html
The current paper presents the free vibration characteristic of axially moving conical shells made of shape memory alloy based on Donnell&rsquo;s shell theory. The material behavior is simulated based on the Boyd-Lagoudas model. By applying the suitable airy function, the strain compatibility equation, and the Galerkin method, two sets of equations of motion are obtained. The compatibility equation is solved by using the steady-state form of equations and employing the suitable flexural mode shape concerning radial displacement. The effects of moving in the axial direction and using the SMA are investigated with the aid of the frequency responses curves. The phase transformation would decrease the quantity of the critical velocity. The results have been evaluated by means of the available data.Theoretical Study of Effective Parameters in the Friction Reduction by Ultrasonic Vibrations in Solid Surfaces
https://jmee.isme.ir/article_696965.html
Ultrasonic vibrations are used in many fields to reduce friction forces. In this paper, the reasons for reducing friction in solid surfaces are investigated using the friction model of Dahl and the elastic-plastic contact model. Based on the theoretical model, four parameters: relative velocity, contact surface, the distance between surfaces, and Young modulus, are effective in the frictional force reduction. This study is validated using experimental tests. The results showed that the effects of oscillations of the relative velocity and changes of contact surfaces on the friction reduction are 51% and 12%, respectively. The minimum effect, among the factors, was related to the Young modulus with a value of 1%. The reason for the force reduction is the nonlinear behavior of the contact surface, contact stiffness, and the friction force functions. Moreover, fluctuations in their input parameters cause an asymmetric oscillation in the value of those functions. This feature changes these functions&rsquo; average value and reduces the friction forces.Transient response of a functionally graded piezoelectric rectangular plane with multiple cracks under electromechanical impacts
https://jmee.isme.ir/article_700936.html
Analytical method is developed to examine fracture behavior of a functionally graded piezoelectric rectangular plane (FGPRP) with finite geometry under impact loads. The material properties of the FGPRP vary continuously in the transverse direction. Two different types of boundary conditions are examined and discussed in the analyses. The finite Fourier cosine and Laplace transforms are employed to obtain stress and electric displacement fields in the finite plane containing electro-elastic screw dislocation. Based on the distributed dislocation technique, a set of integral equations for the finite plane is weakened by multiple parallel cracks under electromechanical impact loads. By solving numerically, the resulting singular integral equation, the dynamic stress intensity factor (DSIF) is obtained for the electrically impermeable case. The new results are provided to show the applicability of the proposed solution. The effects of the geometric parameters including plate length, width, crack position, crack length, loading parameter, and FG exponent on the dynamic stress intensity factors are shown graphically and discussed.Nonlinear Coupled Thermoelasticity of Functionally Graded Cylindrical Shells Resting on Elastic Foundation
https://jmee.isme.ir/article_707982.html
Kinematically nonlinear coupled thermoelasticity of the FGM cylindrical shell resting on elastic foundations is investigated under heat shock. The energy and equations of motion are solved simultaneously as a system of equations for an FG cylindrical shell. It is assumed that the shell is resting on the nonlinear Winkler elastic foundation. The classical theory of coupled thermoelasticity along with the first order shear deformation shell theory are used to solve the problem. The finite element method is employed to numerically solve the problem in the space domain and the Newmark method in time domain. Temperature distribution across the shell thickness is considered to be linear. The radial displacement distributions for different values of the power law index and the Winkler coefficients are plotted in terms of time.Experimental study of parameters affecting friction reduction in solid-liquid interfaces using ultrasonic vibrations
https://jmee.isme.ir/article_707997.html
The utilization of ultrasonic waves is a method to reduce frictional drag. Available hypotheses state that ultrasonic vibrations reduce frictional drag by creating cavitation, forming a fluid vapor layer surrounding the surface, and reducing its contact surface. This paper examines the hypothesis by performing experimental tests to eliminate the cavitation effect via increasing the pressure and investigates other factors affecting the frictional drag reduction. Experimental tests showed that by applying ultrasonic vibrations, frictional drag is reduced by an average of about 9%. Besides, by eliminating the cavitation effect, the frictional drag reduction is nearly 6%. It reveals that about 3% of frictional drag reduction was related to cavitation. The shear stress relation shows that the effect of variation of shear surface and distance in the presence of ultrasonic vibrations are negligible, and therefore the only factor that affects the drag force reduction is viscosity. It can be hypothesized that ultrasonic vibrations reduce viscosity by mechanisms such as increasing both local temperature and the distance between molecules. The tests showed that the viscosity was reduced by 6% by using ultrasonic waves.Multi-objective optimization of two-layer microbeam used for sensing of viruses
https://jmee.isme.ir/article_707998.html
In this paper, new optimizations of the two-layer microbeams based on the classical and non-classical theory are presented. In the first step, the natural frequency is obtained based on the modified couple stress theories. In the second step, three important functions of the microbeams which are used as microsensors, sensitivity, quality factor, and maximum stress are defined. Then, in the third step, two and three objective optimizations are done by using the genetic algorithm. In the two objective optimization, sensitivity and quality factor are selected as objective functions. In the three objective optimization, the maximum stress adds to the objective functions. The geometric parameters are design variables and there are some constraints and limits for those. The results are presented based on the classical and non-classical theory and optimal points are obtained for each optimization by using MATLAB.