Scientia Iranica
Volume:29 Issue: 1, Jan-Feb 2022

This study examines the mechanical safety of a gas lift completion string in a certain oil eld, Algeria 438B block, having complex geological characteristics (a high salt and high-pressure sandwich). When an annulus is not supported within uid column after unloading by using conventional single-tube gas lift completion with positive lift oil production, inner pressure is so low that the pressure di erential between the annulus and external casing is very large, which may damage the casing. Hence, a dual tube completion annulus lled with uid that can resist pressure was used to overcome this problem in adjacent blocks using a gas lift production string with positive and reverse lift oil. However, this technology is complex and characterized by poor system reliability, large construction costs, and maintenance diculty. By considering the three aspects of a casing string, squeeze strength, tensile strength, and internal pressure strength, a gas lift completion string with dual concentric tubes and positive lift was preferably selected under conditions that were veri ed to be safe for production and a shut-in state. This gas lift completion string design was shown to be feasible and had no problem of completion string in adjacent blocks.

The present study investigates the design of a very low head axial ow turbine using surrogate-based optimization. The design variables were blade angles between guide vanes and runner blades with the objective function of turbine eciency. A Latin hypercube sampling method was initially used to design the experiment with thirty sampling points, and a large eddy simulation was modeled to analyze the ow for all sampling points. The correlation between the design variables and turbine eciency was then evaluated using surrogate models while the optimal design variables were identi ed. In addition, several optimizers were employed to tackle the proposed problem and evaluate their performance. The optimal design of blade angles.

This paper presents the bending analysis of simply supported Functionally Graded (FG) size-dependent beams based on modi ed strain gradient theory. Shear and normal deformations are considered in displacement eld according to hyperbolic shear deformation theory. Governing equations and corresponding boundary conditions for FG micro beam are derived utilizing principle of minimum total potential energy. Mori- Tanaka homogenization scheme and the classical rule of mixture are used for prediction of material properties through the thickness. E ects of Winkler-Pasternak elastic foundation parameters are studied at di erent side-to-thickness ratios. E ects of di erent aspect ratios, elastic foundation parameters, power law gradient indexes, and di erent loading conditions are investigated. The eciency and accuracy of the presented model is demonstrated against the existing results in particular cases.

Nowadays, researchers are very interested to investigate the dynamic behavior of thin-walled structures during the machining process due to their broad application in aerospace, automotive industries, etc. One of the main problems in the machining of thin- walled structures is unstable chatter vibrations, which causes poor machined surface quality and decreases the system life span. Therefore, the main aim of this paper is to propose a practical method to solve the chatter instability problem during the milling process of thin- walled components. To this end, rst, the e ects of geometrical parameters like workpiece height, thickness, tool overhang, diameter, and their ratios on the chatter stability are inves- tigated. Based on the mentioned parameters, three-dimensional Stability Lobe Diagrams (SLDs) are presented for the rst time in which one can use the diagrams to switch the unstable machining process to a stable one by changing the values of the system parameters. Finally, the results obtained by the experimental test show that the presented three- dimensional diagrams can be utilized to avoid chatter instability in the milling process.

High-Pressure Die Casting (HPDC) is one of the major production processes of the automotive industry, widely used to manufacture geometrically complex nonferrous castings. The mechanical strength and microstructure of HPDC-manufactured products change with variation in several process parameters such as injection pressure, molten temperature, 1st and 2nd stage plunger velocities, cooling temperature, etc. Since these process parameters directly a ect casting quality, their optimum combination is needed to maximize productivity of the process and minimize casting defects such as porosity, pinholes, blowholes, etc. Hence, to tackle this problem, an approach is presented in this paper that minimizes the major casting defect, i.e., porosity, in the HPDC process by optimizing parameters through Design Of Experiments (DOE) in combination with Taguchi Analysis. The obtained results showed that cooling time, injection pressure, and 2nd stage plunger velocity had a major in uence on the response factor (density of the cast part). It was further concluded that by using a 178-bar injection pressure, 665C molten temperature, 5 seconds of cooling time, 210C mold temperature, 0.20 m.s

The aim of this study is to develop a combined approximation technique to nd a numerical solution to the foam drainage equation in various absorption and distillation processes. In this approach, rst, discretization of time is performed with the aid of the Taylor expansion series. Hence, a collocation method based on novel Bessel polynomials is utilized for the space variable. Thus, the solution is found by solving a linear system of algebraic equations in each time step. Numerical simulations are provided to check the accuracy and eciency of the presented algorithm. The numerical results are compared with exact solutions as well as the outcomes of other existing numerical methods.

This study attempts to investigate the e ect of Fused Deposition Modeling (FDM) process parameters on mechanical characteristics with Taguchi optimization method. Three di erent FDM process parameters including lling structures (rectilinear, triangular, and full honeycomb), occupancy rates (10, 30, and 50%), and table orientation (0, 60, and

This paper explores the e ects of thermal radiation, buoyancy force, chemical reaction, and activation energy on magnetohydrodynamic (MHD) nano uid ow past a stretching vertical surface. The non-linear momentum, energy, solute, and nanoparticle concentration boundary layer equations are simpli ed using similarity transformations. The transformed equations are numerically solved using the shooting technique. Corresponding results for dimensionless velocity, temperature, solute, nanoparticle concentration pro les, skin friction, local Nusselt number, local Sherwood number, and local nanoparticle Sherwood number are shown for various related parameters. It is observed that the temperature and concentration pro les of nanoparticles increased with the increase in the parameters of thermal radiation and the temperature di erence. With increasing regular buoyancy parameters, the local Nusselt number decreased by increasing the adaptation rate, the Biot number, and the thermal radiation parameters.

There is a global trend to optimize energy harvesting from all energy resources including renewable energy. This study focuses on the enhancement of the surface of anges in anged shrouded wind turbines so as to obtain more ecient systems. To this end, a Computational Fluid Dynamics (CFD) approach is utilized. All models are identical in terms of entrance diameter, exit diameter, length of the di user, and the height of the ange. However, each model is of di erent ange surface types. Di erent surfaces including a simple surface and some furrowed surfaces are studied. The validation reports show that there is a strong correlation between the outcomes of the present study and previous experimental results. The results demonstrate that the models with furrowed surface ange yield increase in the wind velocity when approaching the wind turbine blades. This leads to about 5{7% more output power. Also, the results indicate that maximum velocity occurs at about 5 cm after the shroud entrance. Consequently, it is suggested that the wind turbine be installed at the mentioned location inside the shroud to obtain the optimum energy harvest.

This study aims to investigate the consistency between the results obtained from the turning operation. To this end, Ti 6Al-4V alloy workpiece was machined using CNC lathe. In addition, surface roughness (Ra), vibration, and energy consumption values were determined through turning. Experimental results were then analyzed statistically. Response Surface Method (RSM) and grey relational analysis were employed for statistical analysis. According to RSM analysis, grey relational analysis, and ANOVA and regression analysis, the feed rate was found the most e ective parameter that negatively a ects surface roughness, energy consumption, and vibration. Finally, the steps involved in conducting grey relational analysis and the process of obtaining the results were examined.