Shahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947515320250723Multi-Objective Optimization of the Natural Gas-Air Venturi-Type Mixer for Bi-Fuel EnginesMulti-Objective Optimization of the Natural Gas-Air Venturi-Type Mixer for Bi-Fuel Engines165182361210.22044/jsfm.2025.15858.3944FAMohammadaliSalariM.Sc., Mech. Eng., Arak Univ., Arak, Iran.RafatMohammadiAssoc. Prof., Mech. Eng., Arak Univ., Arak, Iran.Journal Article20250303In the conversion of gasoline engines to natural gas, the mixer plays a crucial role in engine performance. This study presents a three-dimensional numerical simulation and geometric optimization of a natural gas-air Venturi-type mixer for a bi-fuel engine. The parametric study revealed that among the examined geometric parameters, increasing the number of orifices from 2 to 8 had the most significant impact, reducing the air-to-fuel ratio by 71% and increasing the uniformity index by 122.7%. Additionally, increasing the orifice diameter from 1 to 2.5 mm had a greater effect on the air-to-fuel ratio (44% decrease), while increasing the throat diameter from 17 to 20 mm had a greater effect on the uniformity index (17.9% decrease). A multi-objective genetic algorithm was employed to minimize deviations of the air-to-fuel ratio from the stoichiometric value and to maximize the uniformity index. The optimization results showed that in the geometry with the lowest deviation from the stoichiometric air-to-fuel ratio, this deviation and the uniformity index decreased by 99% and 39.7%, respectively, compared to the base-mode. Conversely, in the geometry with the highest uniformity index, this parameter increased by 16%, while the air-to-fuel ratio deviation increased by 32.6% relative to the base-mode.In the conversion of gasoline engines to natural gas, the mixer plays a crucial role in engine performance. This study presents a three-dimensional numerical simulation and geometric optimization of a natural gas-air Venturi-type mixer for a bi-fuel engine. The parametric study revealed that among the examined geometric parameters, increasing the number of orifices from 2 to 8 had the most significant impact, reducing the air-to-fuel ratio by 71% and increasing the uniformity index by 122.7%. Additionally, increasing the orifice diameter from 1 to 2.5 mm had a greater effect on the air-to-fuel ratio (44% decrease), while increasing the throat diameter from 17 to 20 mm had a greater effect on the uniformity index (17.9% decrease). A multi-objective genetic algorithm was employed to minimize deviations of the air-to-fuel ratio from the stoichiometric value and to maximize the uniformity index. The optimization results showed that in the geometry with the lowest deviation from the stoichiometric air-to-fuel ratio, this deviation and the uniformity index decreased by 99% and 39.7%, respectively, compared to the base-mode. Conversely, in the geometry with the highest uniformity index, this parameter increased by 16%, while the air-to-fuel ratio deviation increased by 32.6% relative to the base-mode.https://jsfm.shahroodut.ac.ir/article_3612_e988338be24022e93cb3adc1c80b62d2.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947515320250723Investigation of the buckling behavior of cylindrical unanchored steel storage tank under near field 3-D seismic loadingInvestigation of the buckling behavior of cylindrical unanchored steel storage tank under near field 3-D seismic loading183198361110.22044/jsfm.2025.15901.3957FAMotaharehNiazuniversity of science and cultureAliNikkhooProf., Faculty of Civil Engineering of University of Science and Culture, Tehran, Iran.NaderKhajehahmad AttariBuilding and Housing Research CenterJournal Article20250414Maintaining the health of oil and other fluid storage tanks after an earthquake is one of the most important points for any earthquake-prone country. By examining the dynamic response of storage tanks in past earthquakes, it can be seen that steel storage tanks are more vulnerable than concrete tanks. Therefore, it is more important to investigate the seismic behavior of steel tanks. In this study, tank and the fluid inside it and interaction between fluid and structure in the ABAQUS software is simulated, to investigate the buckling behavior of an unanchored broad cylindrical steel storage tank built in Malayer. some near field earthquakes records are applied to storage tank. and all three components of these records, have been considered. the radial displacement of wall of the tank after the earthquake indicate the diamond-shaped buckling mode due to the significant effects of slashing. It should also be mentioned that the most deformations are observed at a height of 10.5 meters from the ground level on the wall of the tank, which due to the lower thickness of the sheet in the upper courses of the wall it can be strengthened in order to prevent the leaking of fluid inside the tank.Maintaining the health of oil and other fluid storage tanks after an earthquake is one of the most important points for any earthquake-prone country. By examining the dynamic response of storage tanks in past earthquakes, it can be seen that steel storage tanks are more vulnerable than concrete tanks. Therefore, it is more important to investigate the seismic behavior of steel tanks. In this study, tank and the fluid inside it and interaction between fluid and structure in the ABAQUS software is simulated, to investigate the buckling behavior of an unanchored broad cylindrical steel storage tank built in Malayer. some near field earthquakes records are applied to storage tank. and all three components of these records, have been considered. the radial displacement of wall of the tank after the earthquake indicate the diamond-shaped buckling mode due to the significant effects of slashing. It should also be mentioned that the most deformations are observed at a height of 10.5 meters from the ground level on the wall of the tank, which due to the lower thickness of the sheet in the upper courses of the wall it can be strengthened in order to prevent the leaking of fluid inside the tank.https://jsfm.shahroodut.ac.ir/article_3611_6b5cf67aab8d6466a05e87e36de29e10.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947515320250723Numerical and Experimental study of a vibro- impact bistable piezoelectric cantilever beam energy harvesterNumerical and Experimental study of a vibro- impact bistable piezoelectric cantilever beam energy harvester199213361410.22044/jsfm.2025.14951.3883FAMostafaShahsavarMechanical engineering, Semnan university, Semnan, IranMohammad MahdiKhatibiFaculty of Department of Solid Design and Applied Design, School of Mechanical EngineeringMohammad RezaAshoryAssoc. Prof., Modal Analysis (MA) Research Laboratory, Faculty of Mechanical Engineering, Semnan University, Iran.Journal Article20240816In this paper, in order to increase the frequency bandwidth, a bistable unimorph piezoelectric cantilever beam energy harvester is equipped with a unilateral barrier to limit the oscillation amplitude. This novel design is recognized as a bistable vibro-impact energy harvester. The main objective of this work is to investigate the effects of vibro-impact behavior on the frequency bandwidth of a typical bistable energy harvester. Initially, by employing Euler-Bernoulli beam assumption and energy method, the governing equations of motion were derived. Subsequently, by numerically solving the governing equations, the frequency bandwidth and harvested power of the system in both typical bistable and vibro- impact bistable systems were compared. According to the obtained results, it was clear by exploiting the vibro- impact behavior, the frequency bandwidth of a typical bistable energy harvester could be increased up to 90%. Then, the effects of initial gap between barrier and cantilever beam on the system's frequency bandwidth were investigated. In this study, some experiments were conducted to evaluate the efficiency of the proposed model and to validate the obtained results.In this paper, in order to increase the frequency bandwidth, a bistable unimorph piezoelectric cantilever beam energy harvester is equipped with a unilateral barrier to limit the oscillation amplitude. This novel design is recognized as a bistable vibro-impact energy harvester. The main objective of this work is to investigate the effects of vibro-impact behavior on the frequency bandwidth of a typical bistable energy harvester. Initially, by employing Euler-Bernoulli beam assumption and energy method, the governing equations of motion were derived. Subsequently, by numerically solving the governing equations, the frequency bandwidth and harvested power of the system in both typical bistable and vibro- impact bistable systems were compared. According to the obtained results, it was clear by exploiting the vibro- impact behavior, the frequency bandwidth of a typical bistable energy harvester could be increased up to 90%. Then, the effects of initial gap between barrier and cantilever beam on the system's frequency bandwidth were investigated. In this study, some experiments were conducted to evaluate the efficiency of the proposed model and to validate the obtained results.https://jsfm.shahroodut.ac.ir/article_3614_bc82387763871696cd58792f09e722a9.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947515320250723A Computational Analysis of the Aerodynamic Behaviors of the Low-Speed Conventional AirfoilsA Computational Analysis of the Aerodynamic Behaviors of the Low-Speed Conventional Airfoils215221360910.22044/jsfm.2025.16052.3958FAHosseinAnsarianAerospace Department, Malek Ashtar University of Technology, Tehran, IranAlirezaDavariDepartment of Mechanical and Aerospace Engineering, SR.C., Islamic Azad University, Tehran, IranJournal Article20250413This paper investigates the aerodynamic characteristics of NACA airfoils 0012, 0015, and 4415 in the low Reynolds number range of 500 to 2000. Simulations have been performed using a high-resolution two-dimensional incompressible flow code, using the immersed boundary method with a sharp interface and the unsteady Navier-Stokes equations. The goal of this study is to provide a database of variations in force coefficients, center of pressure, and Strouhal numbers as functions of Reynolds number, angle of attack (5 to 40 degrees), and airfoil shape. The results reveal that low Reynolds number flows exhibit significant complexity due to phenomena such as Karman vortex shedding and leading-edge vortex (LEV) formation and shedding. These behaviors result in significant fluctuations in aerodynamic coefficients, especially near stall, thus the simulation shoud be performed with adequate temporal accuracy. The effect of airfoil shape is primarily observed in the lift-to-drag ratio and center of pressure, with the NACA 4415 airfoil demonstrating the highest aerodynamic performance. Comparison of simulation results with available experimental data at both low and high Reynolds numbers confirms the validity of the employed numerical model. This database serves as a reference for designing small aircraft, unmanned aerial vehicles, and bio-inspired flight systems. Additionally, the obtained data can aid in improving and validating computational models.This paper investigates the aerodynamic characteristics of NACA airfoils 0012, 0015, and 4415 in the low Reynolds number range of 500 to 2000. Simulations have been performed using a high-resolution two-dimensional incompressible flow code, using the immersed boundary method with a sharp interface and the unsteady Navier-Stokes equations. The goal of this study is to provide a database of variations in force coefficients, center of pressure, and Strouhal numbers as functions of Reynolds number, angle of attack (5 to 40 degrees), and airfoil shape. The results reveal that low Reynolds number flows exhibit significant complexity due to phenomena such as Karman vortex shedding and leading-edge vortex (LEV) formation and shedding. These behaviors result in significant fluctuations in aerodynamic coefficients, especially near stall, thus the simulation shoud be performed with adequate temporal accuracy. The effect of airfoil shape is primarily observed in the lift-to-drag ratio and center of pressure, with the NACA 4415 airfoil demonstrating the highest aerodynamic performance. Comparison of simulation results with available experimental data at both low and high Reynolds numbers confirms the validity of the employed numerical model. This database serves as a reference for designing small aircraft, unmanned aerial vehicles, and bio-inspired flight systems. Additionally, the obtained data can aid in improving and validating computational models.https://jsfm.shahroodut.ac.ir/article_3609_6564c710d2c8ac04b90d0081cef57c02.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947515320250723Estimating the amount of water loss due to evaporation in the Kalpoosh dam of Semnan province and investigating its reduction methodsEstimating the amount of water loss due to evaporation in the Kalpoosh dam of Semnan province and investigating its reduction methods223229361010.22044/jsfm.2025.15984.3956FAHasanShekariMechanical Engineering Department, Shahrood University of TechnologyAhmadNazariAssist. Prof., Mech. Eng., Shahrood Univ., Shahrood, Iran.Journal Article20250416In arid and semi-arid regions, the main cause of water loss can be considered the phenomenon called surface evaporation. It is an inevitable phenomenon and according to the location and weather conditions of the countries, it plays an important role in the loss of water resources in a country. In this research, the rate of evaporation in the Kalpoosh dam located in Semnan province has been estimated, taking into account the climate and weather conditions, etc., the rate of evaporation has been calculated using various methods, experimental formulas, and water balance measurements, and in the following, the most optimal method and The appropriate evaporation coefficient was chosen to estimate evaporation. According to the calculations, Ivanov's experimental method with the least amount of error has the best overlap with the amount of observed evaporation from the pan, and the appropriate coefficient of evaporation was examined from among the coefficients between 0.6 and 0.9, and the coefficient of 0.85 was chosen with the least error. And then in the next rank, the experimental formula of the American Civil Engineering Organization was selected. Other methods cannot be used for the Kalpoosh dam due to the calculation of the lack of steam pressure in those formulas and the possibility of calculation errors with the actual value.In arid and semi-arid regions, the main cause of water loss can be considered the phenomenon called surface evaporation. It is an inevitable phenomenon and according to the location and weather conditions of the countries, it plays an important role in the loss of water resources in a country. In this research, the rate of evaporation in the Kalpoosh dam located in Semnan province has been estimated, taking into account the climate and weather conditions, etc., the rate of evaporation has been calculated using various methods, experimental formulas, and water balance measurements, and in the following, the most optimal method and The appropriate evaporation coefficient was chosen to estimate evaporation. According to the calculations, Ivanov's experimental method with the least amount of error has the best overlap with the amount of observed evaporation from the pan, and the appropriate coefficient of evaporation was examined from among the coefficients between 0.6 and 0.9, and the coefficient of 0.85 was chosen with the least error. And then in the next rank, the experimental formula of the American Civil Engineering Organization was selected. Other methods cannot be used for the Kalpoosh dam due to the calculation of the lack of steam pressure in those formulas and the possibility of calculation errors with the actual value.https://jsfm.shahroodut.ac.ir/article_3610_ad7bb8c4e3262b4f0cd0a2f1281b95fd.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-947515320250723Numerical Investigation of Grazing Flow on a Micro Perforated Plate LinerNumerical Investigation of Grazing Flow on a Micro Perforated Plate Liner231239361310.22044/jsfm.2025.15629.3932FAMahdiMoaveni TajoddinPhD student, Ministry of Science, Research & Technology, Aerospace Research Institute, Iran.ImanBahman-JahromiAssist. Prof., Ministry of Science, Research & Technology, Aerospace Research Institute, Iran.HasanNasehAssist. Prof., Ministry of Science, Research & Technology, Aerospace Research Institute, Iran.Journal Article20250123This study investigates the background flow field of a micro-perforated plate (MPP) liner for acoustic analysis under grazing airflow conditions. A segment of the MPP liner is modeled, and the three-dimensional Navier-Stokes equations are numerically solved using a carefully designed computational mesh. A turbulence model is employed to account for flow disturbances, and a fully developed flow boundary condition is applied at the channel entrance to optimize computational cost. The numerical results are validated against experimental data from previous studies. The impact of flow Mach number on two key mechanisms influencing the acoustic behavior of the liner is examined: (1) the vertical velocity component at the hole openings, and (2) vortex generation at and downstream of the holes. As the Mach number at the inlet of the duct increases, the amount of rotation of the vertical component of velocity along the hole also increases, which leads to changes in the acoustic properties of the liner, including its impedance. In other words, the generation of vortices downstream of the hole increases with increasing Mach number. Findings reveal that an increase in Mach number leads to higher acoustic impedance, highlighting the complex interplay between flow dynamics and acoustic performance.This study investigates the background flow field of a micro-perforated plate (MPP) liner for acoustic analysis under grazing airflow conditions. A segment of the MPP liner is modeled, and the three-dimensional Navier-Stokes equations are numerically solved using a carefully designed computational mesh. A turbulence model is employed to account for flow disturbances, and a fully developed flow boundary condition is applied at the channel entrance to optimize computational cost. The numerical results are validated against experimental data from previous studies. The impact of flow Mach number on two key mechanisms influencing the acoustic behavior of the liner is examined: (1) the vertical velocity component at the hole openings, and (2) vortex generation at and downstream of the holes. As the Mach number at the inlet of the duct increases, the amount of rotation of the vertical component of velocity along the hole also increases, which leads to changes in the acoustic properties of the liner, including its impedance. In other words, the generation of vortices downstream of the hole increases with increasing Mach number. Findings reveal that an increase in Mach number leads to higher acoustic impedance, highlighting the complex interplay between flow dynamics and acoustic performance.https://jsfm.shahroodut.ac.ir/article_3613_fbfa65faa3979e923b268c19135457e9.pdf