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Centrifugal pumps performance is highly affected by working fluid viscosity. So, optimization of such pumps for pumping of viscose fluids is very important. In the present paper, multi-objective optimization of the centrifugal pumps is performed to obtain optimum impellers for pumping fluids with various viscosities at different volumetric flow rates. In this way, theoretical head and impeller hydraulic losses are considered as objective functions. Design variables defined in this optimization problem are passage width of impeller and outlet angle of blade. Diagrams of Pareto fronts and Pareto sets are extracted for different viscosities and different volumetric flow rates. Some trade-off optimum design points are selected from all non-dominated points using three different methods namely break point, TOPSIS and near to ideal point. Such methods are defined completely and employed to achieve compromising point successfully. Obtained optimum points contain interesting results which cannot be achieve without using proposed multi-objective optimization approach.

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Heat pipe is an effective device for heat transferring. Using nanofluid as working fluid can significantly increase heat pipe thermal performance. But rate of the performance improvement, is dependent on parameters of the suspended nanoparticles in nanofluid. In this article, for the first time by considering nanoparticle volume fractions and diameters as design variables and the difference between the wall temperature of evaporator and condenser and liquid pressure drop as objective functions, the heat pipe performance has optimized. The used heat pipe is a cylindrical heat pipe with nanofluid as working fluid. Heat pipe thermal performance while using nanofluid has modeled by CFD method and then GEvoM has used to relate between design variables and objective functions. Using the modified NSGAII approach, pareto front has plotted and the values of recommended optimum points has obtained by mapping method. Recommended design points unveil interesting and important optimal design principles that would not have been obtained without the use of a multi-objective optimization approach.

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In this paper, the sound behavior of a double walled composite with an intermediate porous layer has been conducted using the classical laminated plate theory (CLPT). The main objective of the paper is devoted to considering the analytical study of various boundaries on porous layers as well as parameter study on power transmission through the structure. Thus, viscous and inertia coupling in a dynamic equation, as well as stress transfer, thermal and elastic coupling of porous material are considered based on Biot theory. In addition, the equation of wave propagation are extracted according to vibration equation of composite layers. Then, with applying the various boundaries on the structures along with solving these equations simultaneously, the Transmission Loss (TL) is calculated. The analytical results are compared with both numerical ones obtained from Statistical energy Analysis (SEA) as well as empirical results and an excellent agreement is observed. The parametric studies are presented to investigate the effects of boundary conditions on TL. The results indicate that the interface of porous-composite layers as well as stacking sequences of the composite layers would play an important role in reduction of power transmission through the structure.

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In this study, a three-dimensional fluid field of an axial flow type micro hydro named Agnew has been investigated. The turbine installed at the Hydrulic Machines Laboratory (HML) of Iranian Research Organization for Science and Technology has been designed to generate 1 kw output power.All numerical simulations were performed using ANSYS CFX, a Computational Fluid Dynamic code, to investigate the performance parameters, such as efficiency and power, and results are validated against experimental data. Four different grid sizes are studied in accordance with the Grid Convergence Index (GCI) to investigate mesh independency of the solution. Results of several turbulence models were also examined to find out the Shear Stress Transport (SST) model in order to take into account the turbulence in the flow. Several turbulence models were also examined together with wall function in order to take into account the turbulence in the flow. A mixing plane interface plane was used to pass the disturbance of rotary domain to stationary domain. The obtained results show that a high resolution advection scheme, mixing plane to model the rotor-stator interaction together with a turbulence intensity of I=6% at the inlet, best matches with the experimental results. The difference between the efficiencies computed from both numerical approaches and experimental values may be ascribed to a numerical error, a model error or a systematic error.

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In this paper, the static stiffness and strength as well as fatigue life of adhesively bonded single lap joint (SLJ) are numerically studied using the cohesive zone model (CZM). In order to simulation of the SLJ using mixed-mode bi-linear CZM, the failure behavior of adhesive in modes II and III is considered the same. Fatigue damage propagation is simulated through scripting USDFLD Subroutine in ABAQUS/Standard. Static stiffness and strength and fatigue life obtained in this study are consistent with experimental results available in literature. Then, the effect of geometric parameters including overlap length, substrate thickness, and tapered substrates are investigated. The obtained results reveal that the increase of the overlap length would lead to increase the static strength and fatigue life prediction. While increasing substrate thickness results improved fatigue life, there are no a known relation between the static strength and substrate thickness due to the changes of the loading modes. Tapered substrates have also positive effect on the strength and fatigue life because of more compatible rotations. Therefore, to improve the strength and fatigue life of a SLJ, authors suggest greater overlap length and thickness along with tapered substrates.

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Inducers are important devices which are mounted upstream of the inlet to the main impeller of the centrifugal pump to achieve higher suction performance and rotate with the same speed as the impeller. Inducers improve the hydraulic performance and lifespan of the pump through increasing the inlet pressure, but the quantity of the improvement is dependent on the geometrical parameters of the inducer. Therefore, the optimization of these parameters is crucial. In the present study, the performance of an inducer is optimized by considering the inlet tip blade angle, the outlet tip blade angle and the ratio of the outlet hub radius to inlet hub radius as design variables and the head coefficient, the hydraulic efficiency and the required net positive suction head as objective functions. The inducer performance is simulated using 3-D computational fluid dynamics and compared with experimental data which shows the validity of the used method and assumptions. The artificial neural network is used to relate between design variables and objective functions. Then, the Pareto fronts are plotted using the modified non-dominated sorting genetic algorithm II and the proposed optimum points are presented using nearest point to the ideal point method. Using multi objective optimization, the head coefficient, the hydraulic efficiency and the net positive suction head are improved 14.3%, 0.3% and 30.2%, respectively. Recommended design points unveil important optimal design principles that would not have been obtained without the use of a multi objective optimization approach.

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