Computational Fluid Mechanics (CFM)
Hamid Reza Nazif
Abstract
Hydrodynamic of a turbulent impinging jet on a flat plate has been studied experimentally and numerically. Experiments were conducted for the Reynolds number range of 72000 to 102000 and a fixed jet-to-plate dimensionless distance of H/d=3.5. Based on the experimental setup, a multi-phase numerical model ...
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Hydrodynamic of a turbulent impinging jet on a flat plate has been studied experimentally and numerically. Experiments were conducted for the Reynolds number range of 72000 to 102000 and a fixed jet-to-plate dimensionless distance of H/d=3.5. Based on the experimental setup, a multi-phase numerical model was simulated to predict flow properties of impinging jets using two turbulent models. Mesh-independency of the numerical model was studied to ensure the preciseness of the results. Numerical and experimental forces on the target plate were compared to examine the performance of turbulent models and wall functions. As a result, the force obtained by the Reynolds stress turbulent model alongside with non-equilibrium wall function was in good agreement with the experiment. The correlation equations were obtained for predicting the water thickness over the target plate and impingement force versus Reynolds number. It was also indicated that the maximum shear stress on the target plate was located at radial dimensionless distance of r/d=0.75.
Energy Science and Technology
Saeed Ahmadipour; Mohammad Hossein Aghkhani; Javad Zareei
Abstract
Start of fuel injection and fuel type are two important factors affecting engine performance and exhaust emissions in internal combustion engines. In the present study, a one-dimensional computational fluid dynamics solution with GT-Power software is used to simulate a six-cylinder diesel engine to study ...
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Start of fuel injection and fuel type are two important factors affecting engine performance and exhaust emissions in internal combustion engines. In the present study, a one-dimensional computational fluid dynamics solution with GT-Power software is used to simulate a six-cylinder diesel engine to study the performance and exhaust emissions with different injection timing and alternative fuels. Starting the fuel injection was from 10 °CA BTDC to the TDC with an interval between two units and from alternative fuel bases (diesel), including methanol, ethanol, diesel, and ethanol compounds, biodiesel and decane was used. To validate the model, a comparison is made between simulation data and experimental data (including torque and power) showing the validation error is less than 6.12% and indicating the software model validation. Also, the modeling results show that decane fuel has higher brake power and brake torque of more than 6.10 % while fuel is injected at 10 °CA BTDC compared to the base fuel, and illustrates a reduction of 5.75 % in specific fuel consumption due to producing higher power. In addition, with the advance of injection timing compared to baseline, the amount of CO and HC in biodiesel fuel reduces to 83.88% and 64.87%, respectively, and the lowest NOX emission with the retardation of starting injection, to decane fuel is awarded. In general, the results show that decane fuel could be a good alternative to diesel fuel in diesel engines when it starts fuel injection at 10 °CA BTDC.
Fluid Mechanics
Vijay Kumar Dwivedi; Pooja Pathak
Abstract
There are many industrial applications of axially grooved journal bearing, especially in turbo- machinery. Stability is a very big issue for researchers, in high speed rotating machines. The axial groove journal bearing has a capacity to reduce the vibration and the ability to resolve the heating problems ...
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There are many industrial applications of axially grooved journal bearing, especially in turbo- machinery. Stability is a very big issue for researchers, in high speed rotating machines. The axial groove journal bearing has a capacity to reduce the vibration and the ability to resolve the heating problems as well as stability at a higher speed. Dynamic performance parameters and stability of axial grooved hybrid journal bearings depend on the dimensions and orientations of the groove to a great extent at higher speeds. In this work, a FORTRAN program is used to solve Reynolds governing equation. The bearing performance characteristics are simulated for the various dimensions and orientation of the groove. Non-linear journal center trajectories are drawn for different Reynolds numbers for stability analysis. It is found that the smaller groove length results in lower bearing capacity, whereas smaller groove width yields higher bearing capacity, and the turbulence decreases the stability. The groove location also strongly affects most performance parameters. The optimum location of the groove axis is obtained between 60° to 90° to the load line.
Mechanics of Materials
Bathini Sidda Reddy; Ch. Ravikiran; K. Vijaya Kumar Reddy
Abstract
The present paper considers the devise and development of a novel theory to examine the flexure analysis of exponentially graded plates exposed to thermal and mechanical loads. The properties such as elastic modulus and thermal modulus are assumed to vary exponentially along the thickness by keeping ...
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The present paper considers the devise and development of a novel theory to examine the flexure analysis of exponentially graded plates exposed to thermal and mechanical loads. The properties such as elastic modulus and thermal modulus are assumed to vary exponentially along the thickness by keeping the poisson’s ratio constant. This theory fulfills the nullity conditions on the upper and lower sides of the exponentially graded plates for transverse shear stress. Hamilton’s principle is used to derive the equation of motion. The present theory’s numerical results are assessed with three-dimensional elasticity solutions and the results of other authors available in the literature. The influence of thermomechanical loads, thickness ratios, and aspect ratios on the bending response of exponentially graded plates are studied in detail. The analytical formulations and solutions presented herein could provide engineers with the potential for the design and development of exponentially graded plates for advanced engineering applications.
Aerodynamics
Sarallah Abbasi; Ali Joodaki
Abstract
In This paper, a parametric study of compressor performances was performed by streamline curvature method (SLC). Effects of three input parameters in design process, e.g., number of blades, distribution of blade thickness, and blade sweep angels, on the main objective parameters in aerodynamic design, ...
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In This paper, a parametric study of compressor performances was performed by streamline curvature method (SLC). Effects of three input parameters in design process, e.g., number of blades, distribution of blade thickness, and blade sweep angels, on the main objective parameters in aerodynamic design, e.g., velocity distribution, efficiency and pressure ratio, has been investigated in the parametric study. Initially, a certain two stage axial compressor has been designed by SLC. Validation of the results is confirmed by comparing the obtained results with the experimental ones. Regarding various values for aforementioned input parameters, the first stage of the axial compressor is redesigned and the output parameter is established. Therefore, the sensitivity of the design results to each of the aforementioned parameters is recognized. Results show that increasing the blades sweep angle causes to improve the flow behavior such as efficiency and pressure ratio in axial fan and reducing it have a completely contrary result. Also, reducing the rotors blades number leads to an increase in the pressure ratio and efficiency while its increase cause to a contrary result. , it is concluded that reduction in the blades number has the stronger effect on the performance parameters than its increment. The results also show that effect of the thickness in the hub is greater than the thickness of the tip and its increase leads to reduce both efficiency and pressure ratio.
Magnetohydrodynamics (MHD)
Mohammad Hasan Taheri; Morteza Abbasi; Mehran Khaki Jamei
Abstract
In this article, a laminar magnetohydrodynamics (MHD) developing flow of an incompressible electrically conducting fluid subjected to an external magnetic field is considered. The aim of the study is to propose a correlation for computing the development length of the laminar MHD developing flow in a ...
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In this article, a laminar magnetohydrodynamics (MHD) developing flow of an incompressible electrically conducting fluid subjected to an external magnetic field is considered. The aim of the study is to propose a correlation for computing the development length of the laminar MHD developing flow in a pipe. A numerical approach is considered to solve the problem. In the first step, the numerical Finite Volume Method (FVM) is conducted to analyze the problem. Hereafter, the artificial neural network (ANN) is used to develop the datasets and in the last step, the curve fitting is applied to find a correlation for prediction of the development length as a function of the Reynolds and Hartmann numbers. In addition, the effect of the problem parameters on the development length are studied. It is found that the development length declines with the increase of the Hartmann number and grows with the rising of the Reynolds number.
Computational Fluid Dynamics (CFD)
Ali Akbar Rashidi; Ehsan Kianpour
Abstract
Natural convection heat transfer is studied numerically in a triangular enclosure. The enclosure is isosceles right triangle and its bottom wall is hot, the hypotenuse is cold and the other wall is adiabatic. Also, a vertical magnetic field is applied in the enclosure; and there is hybrid nanofluid inside ...
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Natural convection heat transfer is studied numerically in a triangular enclosure. The enclosure is isosceles right triangle and its bottom wall is hot, the hypotenuse is cold and the other wall is adiabatic. Also, a vertical magnetic field is applied in the enclosure; and there is hybrid nanofluid inside the enclosure. This study is conducted for Rayleigh numbers of 103-105, the Hartmann numbers between 0-80, and the volume fraction of nanofluid is between 0-2 percent. Based on the obtained results, as the Hartmann number augments, the temperature of the center of the enclosure decreases due to weakening of the heat transfer flow by increasing the magnetic field forces. In addition, as the Hartmann number augments, the streamlines approach to the walls because the horizontal momentum forces decrease when the Hartmann number increases. Furthermore, by increasing the density of nanoparticles, the heat transfer rate increases, and as a result, heat transfer builds up. Finally, heat transfer improves when the hybrid-nanofluid is employed rather than ordinary nanofluid.
