Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 55 7 2023 09 23 Aerodynamic Design of a Hypersonic Glide Vehicle Based on the Cone-Derived Wave rider Configuration Method Aerodynamic Design of a Hypersonic Glide Vehicle Based on the Cone-Derived Wave rider Configuration Method 797 818 5214 10.22060/mej.2023.21415.7539 FA Ramin Abolzadeh Ghadr Aerodynamic Research Center, Technical Engineering, Imam Hossein Comprehensive University, Tehran, Iran 0000-0002-1660-7064 Mohammad Ali Jozvaziri Imam Hossein University, Faculty of Engineering, Aerospace Science Group, Tehran, Iran Mohammad Hadi Islamy Faculty of Engineering. Imam Hussein University Amirhossein Hossein Qadr Aerodynamic Research Center, Imam Hossein University, Tehran, Iran 0000-0002-3318-5799 Journal Article 2022 11 10 Hypersonic glide vehicles are a novel type of hypersonic weapons that have received extensive attention. These vehicles can seriously challenge any defense system by traveling long distances of about thousands of kilometers in the atmosphere at very high speeds up to more than 20 Mach. In this research, the aerodynamic design of a hypersonic glide vehicle has been done based on the wave rider theory and conical-derived wave rider Method. In this study, a parametric method with three parameters, including cone shock angle β, dihedral angle φ, and compression ratio S, was introduced and used as a design code. In the design process, the HTV2 hypersonic glide vehicle was used as a reference model. To achieve configurations with operational dimensions, by changing the design parameters, four-wave rider configurations with the same dimensions as the reference model were identified. By analyzing these four configurations using the computational fluid dynamics method, the configuration with the best aerodynamic and volume results was selected as the preferred design configuration. Compared to the reference model, the preferred configuration has 36% more aerodynamic efficiency and 15% less volume, indicating the efficiency of the used method. Hypersonic glide vehicles are a novel type of hypersonic weapons that have received extensive attention. These vehicles can seriously challenge any defense system by traveling long distances of about thousands of kilometers in the atmosphere at very high speeds up to more than 20 Mach. In this research, the aerodynamic design of a hypersonic glide vehicle has been done based on the wave rider theory and conical-derived wave rider Method. In this study, a parametric method with three parameters, including cone shock angle β, dihedral angle φ, and compression ratio S, was introduced and used as a design code. In the design process, the HTV2 hypersonic glide vehicle was used as a reference model. To achieve configurations with operational dimensions, by changing the design parameters, four-wave rider configurations with the same dimensions as the reference model were identified. By analyzing these four configurations using the computational fluid dynamics method, the configuration with the best aerodynamic and volume results was selected as the preferred design configuration. Compared to the reference model, the preferred configuration has 36% more aerodynamic efficiency and 15% less volume, indicating the efficiency of the used method.

https://mej.aut.ac.ir/article_5214_7417744a2bac776fabe5a09b21c707a2.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 55 7 2023 09 23 Numerical investigation of fluid-structure interaction of a detached flexible plate behind a circular cylinder Numerical investigation of fluid-structure interaction of a detached flexible plate behind a circular cylinder 819 836 5234 10.22060/mej.2023.22073.7561 FA Iman Zahed Department of Mechanical Engineering, Persian Gulf University, Bushehr, 75169, Iran Yasser Amini Department of Mechanical Engineering, Persian Gulf University, Bushehr, 75169, Iran Ehsan Izadpanah Department of Mechanical Engineering, Persian Gulf University, Bushehr, 75169, Iran Journal Article 2022 12 29 Fluid-structural interaction is one of the most challenging phenomena observed in the surrounding environment, which can play a major role in increasing heat transfer, reducing drag and lift coefficients, energy dissipation, and reducing pressure drop. By inspiration from similar phenomena in nature, the dynamic behavior of flexible structures that interact with fluid is recognized as a novel application in industrial processes such as marine equipment, heat exchangers, and fluid transports. So, this phenomenon should be considered as a way to increase efficiency, eliminate defects, and prevent possible damage in industrial issues on a smaller scale. In this study, the effect of a detached flexible plate, which is placed at a specific distance from a circular cylinder, on aerodynamic and thermal parameters is investigated. This study is simulated by the finite volume method and the finite element method, simultaneously, and also kw-SST model is considered as the turbulent flow model. The fin is placed at different distances of 0.5D, 1D, and 1.5D in upstream and downstream of the circular cylinder, where D is the diameter of the cylinder. The results show that placing the fin at a distance 1D from cylinder downstream increases the Nusselt up to 5%. Moreover, the maximum reduction of the drag coefficient is obtained in this situation. Fluid-structural interaction is one of the most challenging phenomena observed in the surrounding environment, which can play a major role in increasing heat transfer, reducing drag and lift coefficients, energy dissipation, and reducing pressure drop. By inspiration from similar phenomena in nature, the dynamic behavior of flexible structures that interact with fluid is recognized as a novel application in industrial processes such as marine equipment, heat exchangers, and fluid transports. So, this phenomenon should be considered as a way to increase efficiency, eliminate defects, and prevent possible damage in industrial issues on a smaller scale. In this study, the effect of a detached flexible plate, which is placed at a specific distance from a circular cylinder, on aerodynamic and thermal parameters is investigated. This study is simulated by the finite volume method and the finite element method, simultaneously, and also kw-SST model is considered as the turbulent flow model. The fin is placed at different distances of 0.5D, 1D, and 1.5D in upstream and downstream of the circular cylinder, where D is the diameter of the cylinder. The results show that placing the fin at a distance 1D from cylinder downstream increases the Nusselt up to 5%. Moreover, the maximum reduction of the drag coefficient is obtained in this situation.

https://mej.aut.ac.ir/article_5234_5d78d182fd5f5510588695863d22ac27.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 55 7 2023 09 23 Experimental Study of Preload and Bolt Arrangement on Composite Joint Performance in Megawatt Wind Turbine's Nacelle Cover and Nose Cone Experimental Study of Preload and Bolt Arrangement on Composite Joint Performance in Megawatt Wind Turbine's Nacelle Cover and Nose Cone 837 856 5236 10.22060/mej.2023.21559.7466 FA Aidin Ghaznavi Renewable Energy Research Department, Niroo Research Institute (NRI), Tehran, Iran 0000-0003-3148-8320 S. Abolfazl Mousaavi Renewable Energy Research Department, Niroo Research Institute (NRI), Tehran, Iran Journal Article 2022 07 05 The nacelle cover and nose cones of most megawatt wind turbines are made of composite sheets. Due to the complex shapes, geometries, and large dimensions of these components, they are composed of several parts that must be assembled using non-permanent mechanical joints, such as bolts. Therefore, it is very important to consider all the effective parameters that affect composite joints. One of the most critical design parameters for bolt connections is the amount of bolt preload or tightening torque. However, increasing the preload without caution is not feasible due to the composite material present on both sides of the joint, as this can potentially damage the composite sheets. As a result, this paper aims to evaluate experimentally the effect of bolt preload or tightening torque on composite joints. To achieve this, identical specimens were fabricated, each with a different bolt tightening torque ranging from 2 Nm to 50 Nm. These specimens were then subjected to a tensile load. After determining the optimal preload force, four different types of arrangements were experimentally tested to find the best bolt arrangement. Finally, by examining various aspects, the best arrangement for connecting different parts of the nacelle cover and nose cone was determined. The nacelle cover and nose cones of most megawatt wind turbines are made of composite sheets. Due to the complex shapes, geometries, and large dimensions of these components, they are composed of several parts that must be assembled using non-permanent mechanical joints, such as bolts. Therefore, it is very important to consider all the effective parameters that affect composite joints. One of the most critical design parameters for bolt connections is the amount of bolt preload or tightening torque. However, increasing the preload without caution is not feasible due to the composite material present on both sides of the joint, as this can potentially damage the composite sheets. As a result, this paper aims to evaluate experimentally the effect of bolt preload or tightening torque on composite joints. To achieve this, identical specimens were fabricated, each with a different bolt tightening torque ranging from 2 Nm to 50 Nm. These specimens were then subjected to a tensile load. After determining the optimal preload force, four different types of arrangements were experimentally tested to find the best bolt arrangement. Finally, by examining various aspects, the best arrangement for connecting different parts of the nacelle cover and nose cone was determined.

https://mej.aut.ac.ir/article_5236_78289d91e9c4adcf4e97d6b3d4df6ae0.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 55 7 2023 09 23 Experimental investigation of the effect of pH on the stability and thermal conductivity of metal oxide nanofluids Experimental investigation of the effect of pH on the stability and thermal conductivity of metal oxide nanofluids 857 874 5266 10.22060/mej.2023.22193.7578 FA Behrouz Raei Department of Chemical Engineering, Mahshahr Branch, Islamic Azad University, Mahshahr, Iran 0000-0001-6031-4245 Journal Article 2023 02 11 The pH level of nanofluids plays an important role in stability and thermal conductivity. However limited studies have been done in this field. In this research, the effect of pH on the stability and thermal conductivity of ZnO-EG nanofluid at concentrations of 0.05 and 0.75% volumetric fraction and MgO-W at concentrations of 0.05 and 0.5% volumetric fraction were investigated. Experimental measurements of the thermal conductivity were performed by a thermal properties analyzer device at a constant temperature of 25 °C. The results showed that the pH strongly affected the stability of nanofluids so that at the pH of the isoelectric point (IEP), complete aggregation and sedimentation were observed. The thermal conductivity of nanofluids has the lowest value at the pH of the isoelectric point, but as the pH moves away from the isoelectric point, the thermal conductivity increases. The highest enhancement in the thermal conductivity of ZnO-EG nanofluid was 63%, which was obtained at a volume fraction of 0.75% and pH = 12. However, the highest enhancement in the thermal conductivity of MgO-W nanofluid was 49%, which was obtained at a volume fraction of 0.5% and pH = 12. Finally, using the experimental results and with the help of curve fitting, equations with good quality were presented to predict the effective thermal conductivity of metal oxide nanofluids. The pH level of nanofluids plays an important role in stability and thermal conductivity. However limited studies have been done in this field. In this research, the effect of pH on the stability and thermal conductivity of ZnO-EG nanofluid at concentrations of 0.05 and 0.75% volumetric fraction and MgO-W at concentrations of 0.05 and 0.5% volumetric fraction were investigated. Experimental measurements of the thermal conductivity were performed by a thermal properties analyzer device at a constant temperature of 25 °C. The results showed that the pH strongly affected the stability of nanofluids so that at the pH of the isoelectric point (IEP), complete aggregation and sedimentation were observed. The thermal conductivity of nanofluids has the lowest value at the pH of the isoelectric point, but as the pH moves away from the isoelectric point, the thermal conductivity increases. The highest enhancement in the thermal conductivity of ZnO-EG nanofluid was 63%, which was obtained at a volume fraction of 0.75% and pH = 12. However, the highest enhancement in the thermal conductivity of MgO-W nanofluid was 49%, which was obtained at a volume fraction of 0.5% and pH = 12. Finally, using the experimental results and with the help of curve fitting, equations with good quality were presented to predict the effective thermal conductivity of metal oxide nanofluids.

https://mej.aut.ac.ir/article_5266_59b85c256f758c22eae6fa45913205db.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 55 7 2023 09 23 Numerical simulation of two consecutive human sneezing and examining the dispersion of the resulting droplets in the surroundings Numerical simulation of two consecutive human sneezing and examining the dispersion of the resulting droplets in the surroundings 875 894 5274 10.22060/mej.2023.22245.7587 FA Alireza Zandaf Department of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran 0009-0008-5534-0316 Ghassem Heidarinejad Department of Mechanical Engineering, Tarbiat Modares University, Tehran, Iran Journal Article 2023 03 05 In the present study, by simulating the process of two consecutive sneezes using a real model of the upper airway of a 65-year-old non-smoking man, the dispersion pattern of droplets resulting from the process of two consecutive sneezes has been investigated. Using computational fluid dynamics, the velocity of airflow during two consecutive sneezes was checked and the k-ω SST turbulence model was used to check the flow. Assuming realistic flow rate changes in both sneezes, the maximum flow rate during sneezing according to the subject's age and gender is equal to 553 L/min. In the present study, the simulation has been carried out by considering a wide range of droplets with diameters of 1 to 1000 microns, and about 2 million drops have been injected into the surrounding environment during the process of two consecutive sneezes. In this study, the temperature of the air in the surrounding environment and the air jet coming out of the respiratory system are assumed to be 24 and 35 degrees Celsius, and the relative humidity of the surrounding environment and the air jet is assumed to be 65 and 95%. The maximum rate of penetration and spread of droplets resulting from two consecutive sneezes in 5 seconds is 19.9 and 7.5% higher than the rate of penetration and distribution of droplets resulting from a single normal sneeze at the same time. Most of the injected droplets have evaporated in the surrounding environment during the process of two consecutive sneezes, and less than 40,000 drops are left in the environment in 5 seconds. In the present study, by simulating the process of two consecutive sneezes using a real model of the upper airway of a 65-year-old non-smoking man, the dispersion pattern of droplets resulting from the process of two consecutive sneezes has been investigated. Using computational fluid dynamics, the velocity of airflow during two consecutive sneezes was checked and the k-ω SST turbulence model was used to check the flow. Assuming realistic flow rate changes in both sneezes, the maximum flow rate during sneezing according to the subject's age and gender is equal to 553 L/min. In the present study, the simulation has been carried out by considering a wide range of droplets with diameters of 1 to 1000 microns, and about 2 million drops have been injected into the surrounding environment during the process of two consecutive sneezes. In this study, the temperature of the air in the surrounding environment and the air jet coming out of the respiratory system are assumed to be 24 and 35 degrees Celsius, and the relative humidity of the surrounding environment and the air jet is assumed to be 65 and 95%. The maximum rate of penetration and spread of droplets resulting from two consecutive sneezes in 5 seconds is 19.9 and 7.5% higher than the rate of penetration and distribution of droplets resulting from a single normal sneeze at the same time. Most of the injected droplets have evaporated in the surrounding environment during the process of two consecutive sneezes, and less than 40,000 drops are left in the environment in 5 seconds.

https://mej.aut.ac.ir/article_5274_59ab3ba90ae4b4ab84fe69de7b8e3f5f.pdf

Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 55 7 2023 09 23 Numerical Simulation of a Biogas-fueled Solid Oxide Fuel Cell and the Investigation of the Influence of Operating Conditions Numerical Simulation of a Biogas-fueled Solid Oxide Fuel Cell and the Investigation of the Influence of Operating Conditions 895 916 5304 10.22060/mej.2023.22280.7593 FA Morteza Mehrabian Faculty of Mechanical Engineering, University of Guilan, Rasht, Iran Javad Mahmoudimehr Faculty of Mechanical Engineering, University of Guilan, Rasht, Iran Journal Article 2023 03 26 Using biogas, rather than pure hydrogen, in a solid oxide fuel cell (SOFC) can help the green energy production chain. This research investigates the influence of operating conditions on the performance of a biogas-fueled SOFC. In this regard, a 3D numerical model is developed using a finite volume approach and Fluent software. User Defined Functions are employed to introduce the steam reforming processes inside the SOFC. The second-order upwind scheme and SIMPLE algorithm are used for the discretization of governing equations and the pressure-velocity coupling. The results indicate that the power density first increases and then decreases by increasing the steam-to-fuel (S/C) ratio. Increasing the biogas methane content causes the performance of the SOFC to improve by enhancing the rates of reforming reactions. At a voltage of 0.5V and an operating temperature of 1073K, increasing the biogas methane percentage from 45% to 65%, causes the power to increase by 15%. Also, increasing the operating temperature enhances the SOFC performance by increasing the rates of reforming and electrochemical reactions and the electrolyte ionic conductivity. At a voltage of 0.5V, for a biogas methane percentage of 65%, increasing the operating temperature from 1073K to 1273K leads to a 132% growth of power. It is also found that the optimal S/C ratio decreases with temperature and increases with biogas methane content and lies within the range of 0.3-1.2. Using biogas, rather than pure hydrogen, in a solid oxide fuel cell (SOFC) can help the green energy production chain. This research investigates the influence of operating conditions on the performance of a biogas-fueled SOFC. In this regard, a 3D numerical model is developed using a finite volume approach and Fluent software. User Defined Functions are employed to introduce the steam reforming processes inside the SOFC. The second-order upwind scheme and SIMPLE algorithm are used for the discretization of governing equations and the pressure-velocity coupling. The results indicate that the power density first increases and then decreases by increasing the steam-to-fuel (S/C) ratio. Increasing the biogas methane content causes the performance of the SOFC to improve by enhancing the rates of reforming reactions. At a voltage of 0.5V and an operating temperature of 1073K, increasing the biogas methane percentage from 45% to 65%, causes the power to increase by 15%. Also, increasing the operating temperature enhances the SOFC performance by increasing the rates of reforming and electrochemical reactions and the electrolyte ionic conductivity. At a voltage of 0.5V, for a biogas methane percentage of 65%, increasing the operating temperature from 1073K to 1273K leads to a 132% growth of power. It is also found that the optimal S/C ratio decreases with temperature and increases with biogas methane content and lies within the range of 0.3-1.2.

https://mej.aut.ac.ir/article_5304_ce059ef4192cbdcb40df4422c090f1c3.pdf