Scientia Iranica
Volume:29 Issue: 6, Nov-Dec 2022

To extracting power from the wind, the high enough velocity of the wind is the key factor. But, winds with high enough velocities are not available in most areas, and therefore, finding a method to enhance the velocity potential of the low-speed winds has been a serious challenge in wind engineering. In this research study, a hollow duct with a specific configuration, we called Multi-Stage Inducing Duct, is presented which is capable to cause a great enhancement in the velocity profile of the low-speed winds, enough to start most of the small horizontal wind turbines. For example, a three-stage inducing duct can increase the wind velocity from 3 m/s to 9.3 m/s on average at the first stage throat of the duct, which equals an increase of 29-times in wind potential power! This configuration of the duct has been introduced, numerically simulated and the effect of its various geometrical parameters investigated. The effects of wind velocity and the number of the stages on the duct performance are investigated, and finally, a study on the relative effectiveness of adding each of the stages is carried out to help us decide where the upper limit for the number of the stages is.

Circular structures are used in a wide variety of engineering mechanisms and devices. In this paper, an effective algorithm on the basis of the complex mappings is proposed to identify defects in circular structures using Cartesian damage detection techniques. The efficacy of the proposed algorithm is demonstrated through damage identification in circular plates using the Cartesian wavelet analysis. The vibration and thermal responses of the structure, as two important structural signals, are imported into the proposed algorithm to evaluate the abilities of the signals in identifying the damage location and severity. Finally, two experimental tests are conducted to explore the efficacy of the proposed algorithm in real applications.

Magnetorheological (MR) fluid devices operate in a variety of modes, including flow, shear, squeeze, and pinch. Among these, the flow mode is the most efficient one and produces large field-induced pressure differences. Although shear mode is the least effective, it is the most commonly utilized in many applications, including prosthetic knee, due to its ease of construction. In this study, two flow mode designs which are twin rod and rotary vane MR dampers are optimally designed for prosthetic knee application. A multi-objective optimization problem with damping force or equivalent torque and mass as the objectives is formulated and the optimal designs are fabricated and experimentally characterized. The twin rod MR damper is found to produce a damping force of 1020 N at 1 A with an optimal mass of 0.71 kg. The rotary vane MR damper is determined to produce a maximum torque of 33 Nm at 1 A with an optimal mass of 1.1 kg. Finally, the designs are compared with many MR fluid based prosthetic knee design configurations. Based on the results, twin rod MR damper is identified as the optimal design configuration for prosthetic knee application.

A study has been executed numerically on buoyancy induced convection current in a porous container of square shape with the existence of a uniform magnetic flux. The vertical wall situated at the left side is heated with two discrete heaters and the constant temperature is maintained in the right side. There is no thermal transfer in the horizontal walls. This study involves Brinkman Forchheimer-Darcy extended model. The non-dimensional leading equations are evaluated by the finite volume method. The consequences are examined for different values of the porosity, direction of the magnetic flux, Hartmann number, Rayleigh number and Darcy number. The results interpret that the Hartmann number and the average thermal energy transport are disproportionate to each other. Also the averaged heat transfer and the Darcy number are proportionate to each other.

The heat and mass transfer mechanism has gained importance in technical, industrial, and engineering processes due to the application of thermal radiation in nanomaterials with improved thermal properties. The nanomaterials with improved thermal characteristics can be utilized in the formulation of energy to expand the industrial growth of countries. The effects of thermal radiation on the rate-type fluid passing through a Riga plate are examined in this article. The influence of thermophoresis and Brownian motion also have significant importance. The mathematical explanation of the problem is elaborated with the help of partial differential equations. The coupled nonlinear form of ordinary differential equations is achieved via the appropriate methodology of similarity variables. Utilizing suitable MATLAB software, we have achieved numerical solutions for simplified nonlinear equations. The physical parameters have exceptional impacts on the behavior of velocity, temperature, and concentration fields which are explained with the help of graphs. From this study, it is concluded that the Deborah number has an increasing effect on the pattern of fluid velocity. The rising values of the Prandtl number decline the temperature profile while the higher values of the radiation parameter escalate the temperature profile.

Globally, aluminium alloys are being used in many industries. Application of aluminium alloys is realized by many manufacturing processes in which joining processes are inevitable. Joining of aluminium alloys is achieved by various welding processes. One of the appropriate welding processes used to join aluminium alloy is Gas Metal Arc Welding (GMAW). This paper investigates the effect of process parameters of the GMAW process while welding AA 6351 aluminium alloy weldment with the help of an integrated Taguchi–Grey–Fuzzy approach. Taguchi L-16 array was designed by using an orthogonal method to conduct the experiments. From the experimental results, Signal-to-Noise Ratios (S/N ratio) were calculated from which Grey Relational Grades (GRG) were computed. These computed Grey Relational Grades were used as input for the fuzzy controller to find the Grey Fuzzy Relational Grades (GFRG), by which optimized process parameters were found and validated. Furthermore, Analysis of Variance (ANOVA) was used to identify the contributions of the GMAW process parameters over the responses. Subsequently, the effects of process parameters on the weldments were also discussed in detail. By identifying the optimized process parameters and contributing process parameters, the quality of weld joints is improved.

In this study, power conversion efficiency and the analysis of exergy of a grid-connected photovoltaic (PV) power plant was done by comparing solar exergy models for 12 months. Statistical analysis was used to evaluate the PV exergy efficiency related to solar exergy models. First, solar exergy models proposed by Petela, Spanner and Parrott and the mean of solar exergy-to-solar radiation energy ratio were calculated, and the PV exergy efficiency was analyzed. The results indicate that the average solar exergy-to-solar radiation energy ratio for the Samsun region was 0.93 which are related to Petela and Spanner's model. The ratio for Parrott's model was calculated as 0.99. The results confirm that the power conversion efficiency is in the range of 6.15-8.87%. While PV exergy efficiency related to Parrott's model is seen to vary between 4.85% and 7.09% during 12 months, but in Petela's and Spanner's model it changes from 5.19% to 7.60%.

The prime motive of this study is to assess the behavior of curvature-dependent channel boundaries on the MHD peristaltic flow of viscous liquid with heat transportation effects via a curved channel. The analysis is reported by considering the Hall currents, Joule and viscous dissipations effects. Further, no-slip momentum and thermal conditions are incorporated. Mathematical model is subjected to the implication of large wavelength and weaker magnetic Reynolds number schemes. Galilean transformation is used to convert the problem from laboratory frame to wave frame. The solution of the system of equations is executed by employing the numerical method ND Solve (Built-in command in Mathematica). The volume and mean flow rates are computed and examined. Graphical illustrations are provided to evaluate the nature of distinct constraints on velocity, temperature, and rate of heat transportation. Results show that the curvature constraint has significant influences on the mechanical and thermal features of the flow. The damping effects of the magnetic field improve the temperature and rate of heat transportation at the boundary. Moreover, a reduction in thermal transportation rate is noticed for the increasing curvature constraint values.