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Nasiri d., ,
Adami m., ,
Taei, H. ,
Parhizkar h., Publication Date: 2025
Journal Of Applied Fluid Mechanics (17353645) 18(8)pp. 2085-2094
This research presents a numerical simulation of a two-stage launch vehicle's hot stage separation process. Important parameters, such as the separation altitude, flight Mach number, and the angle of attack during separation, were investigated. The effects of these factors and the motor thrust parameter on the distance between the two stages post-separation were evaluated using the Taguchi method. Numerical analysis was performed using ANSYS Fluent, solving the three-dimensional flow field under the six degrees of freedom (6DOF) assumption. The SST k-ω turbulence model was employed for turbulence modeling, with a tetrahedral unstructured mesh used for the computational domain. The simulation results showed that increasing the separation altitude from 10 km to 20 km increased the distance between the two stages by 5.75%, primarily due to reduced air density and drag forces. Raising the flight Mach number from 2 to 3.2 increased the separation distance of two stages by 2.2%. Additionally, a higher angle of attack increased the deviation of the stages from their original trajectory, necessitating stage control after separation. Among the parameters studied, the motor thrust has the most significant effect on increasing the distance between the stages and preventing collisions. In contrast, the angle of attack has the most minor influence. © (2025), (Isfahan University of Technology). All rights reserved.
Mohammadi, M.M. ,
Taei, H. ,
Moosazadeh, H. ,
Sadeghi, M. Publication Date: 2024
Journal of Engineering Mathematics (15732703) 146(1)
An exact three-dimensional hydrodynamic analysis based on the linear potential theory is presented to study the transient liquid sloshing in a prolate spheroidal container which is filled to an arbitrary depth with an inviscid incompressible fluid. Based on this, using the potential fluid theory in the elliptical coordinate system and applying appropriate boundary conditions on the free surface and tank walls, the governing differential equations of the problem were derived. Then, with the proper expansion of orthogonal functions in spheroidal coordinates, the governing partial equations were transformed into a system of ordinary time differential equations. These equations were solved using the Laplace transform and Durbin’s numerical inversion under different external excitations. the natural frequencies and the physical parameters such as the height of the free surface, pressure, force, and overturning moment in the spheroidal containers under external excitation were evaluated and compared with cylindrical and spherical tanks of the same volume. The results of the study show that by increasing the semi-axis ratio in prolate spheroidal and cylindrical tanks, due to the increase in the free surface of the fluid, the natural frequencies decrease in all modes, while in the spherical tank, it increases homogeneously and therefore the natural frequencies remain constant. In addition, the transient pressure, force, and overturning moment response of the prolate spheroidal containers are lower than the cylindrical and spherical tanks with same volume. Consequently, a prolate spheroidal tank, in addition to having a more suitable placement space in the body of the space launcher than the spherical tank, conducts lower destructive sloshing effects compared to both cylindrical and spherical tanks. To validate the results, limiting cases are considered and the validity of results is established in comparison with the data in the existing literature and finite element results using commercial software. © The Author(s), under exclusive licence to Springer Nature B.V. 2024.
Mohammadi, M.M. ,
Taei, H. ,
Moosazadeh, H. ,
Sadeghi, M. Publication Date: 2023
Advances in Aircraft and Spacecraft Science (2287528X) 10(5)pp. 439-455
Free surface fluid oscillation in prolate spheroidal tanks has been investigated analytically in this study. This paper aims is to investigate the sloshing frequencies in spheroidal prolate tanks and compare them with conventional cylindrical and spherical containers to select the best tank geometry for use in space launch vehicles in which the volume of fuel is very high. Based on this, the analytical method (Fourier series expansion) and potential fluid theory in the spheroidal coordinate system are used to extract and analyze the governing differential equations of motion. Then, according to different aspect ratios and other parameters such as filling levels, the fluid sloshing frequencies in the spheroidal prolate tank are determined and evaluated based on various parameters. The natural frequencies obtained for a particular tank are compared with other literature and show a good agreement with these results. In addition, spheroidal prolate tank frequencies have been compared with sloshing frequencies in cylindrical and spherical containers in different modes. Results show that when the prolate spheroidal tank is nearly full and in the worst case when the tank is half full and the free fluid surface is the highest, the prolate spheroidal natural frequencies are higher than of spherical and cylindrical tanks. Therefore, the use of spheroidal tanks in heavy space launch vehicles, in addition to the optimal use of placement space, significantly reduces the destructive effects of sloshing. Copyright © 2023 Techno-Press, Ltd.
Fazeley h.r., ,
Taei, H. ,
Naseh h., ,
Mirshams m., M. Publication Date: 2016
Structural And Multidisciplinary Optimization (16151488) 53(1)pp. 145-160
Space propulsion systems play an increasingly important role in planning of space missions. The traditional method for design of space propulsion systems includes numerous design loops, which does not guarantee to reach the best optimal solution. Multidisciplinary Design Optimization (MDO) is an approach for the design of complex systems that considers a design environment with multiple disciplines. The aims of this study are to implement and compare Multidisciplinary Feasible and Collaborative Optimization architectures for the multi-Objective optimization of a bi-propellant space propulsion system design. Several disciplines such as thrust chamber, cooling, and structure were exploited in a proper combination. The main optimization objectives in the MDO frameworks were to minimize the total wet mass and maximize the total impulse by considering several constraints. Furthermore, Genetic Algorithm and Sequential Quadratic Programming are employed as the system-level and local-level optimizers. The presented design methodology provides an interesting decision making approach to select the best system parameters of space propulsion systems under conflicting goals. © 2015, Springer-Verlag Berlin Heidelberg.
Mirshams m., M. ,
Taei, H. ,
Ghobadi, M. ,
Haghi, H. Publication Date: 2015
Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering (09544100) 229(8)pp. 1510-1530
This article describes the details of an advanced Spacecraft Attitude Dynamics Simulator (SADS) at the Space Research Laboratory (SRL) at the K. N. Toosi University of Technology. This dumbbell style simulator is based on a spherical air-bearing and employed to develop, improve, and carry out operational tests of sensors, actuators, and attitude control algorithms in experimental framework. The SADS facility includes a variety of components: cold gas propulsion system, complementary inertial measurement unit, on-board processor, semi-automatic mass balancing mechanism, and power supply unit. The overall design of SADS and its components is pretty complicated when considering the mission requirements, operational constraints, and functional limitations imposed by construction procedures. To address this complication, an accurate design and development (or selection) process for each subsystem is presented, which attempts to consider the subsystems interactions and improve cost of operation. The SADS facility is now operated in SRL and the results of its simulated and operational maneuvers are described in detail. © IMechE 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
Mirshams m., M. ,
Naseh h., ,
Taei, H. ,
Fazeley h.r., Publication Date: 2014
Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering (09544100) 228(14)pp. 2587-2603
This paper presents an extension of fuzzy-multi-objective genetic algorithm (MOGA) optimization methodology that could effectively be used to find the overall satisfaction of objective functions (selecting the design variables) in the early stages of design process. The coupling of objective functions due to design variables in an engineering design process will result in difficulties in design optimization problems. The primary application of this methodology is the design of a liquid propellant engine with the maximum specific impulse and the minimum weight. The independent design variables in this model are combustion chamber pressure, exit pressure, oxidizer to fuel mass flow rate. To handle the mentioned problems, a fuzzy-multi-objective genetic algorithm optimization methodology is developed based on Pareto optimal set. Liquid propellant engine, F-1 is modeled to illustrate accuracy and efficiency of proposed methodology. © © IMechE 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
Mirshams m., M. ,
Vahid d., M.A. ,
Taei, H. Publication Date: 2010
5pp. 475-483
Simulation is one of the best methods for education and understanding events and used in many fields of science, for example: space researches. For this reason, creating of a frictionless environment that can simulate the operations of satellites will be very usable and appropriate. Spherical air bearings, that we call them TESTBEDs in this paper, are one of the most common devices used in satellite attitude dynamics simulation, because they provide three degrees of freedom rotational motion. They are employed to develop, improve and carry out operational tests of sensors, actuators and attitude control algorithms in experimental framework. An explanation about system engineering tool for testbed design that used by our team in Space Research Lab will be presented in this paper. This systems engineering tool utilizes a testbed-based approach to efficiently track information regarding the mass, cost, operation and volume of simulator subsystems. This subsystem information is derived through a variety of means, including analytical relationships, iterative solvers, and databases of components appropriate for satellite simulators. Finally, a description of 3-DoF satellite simulator and it's subsystems (manufactured in Space Research Lab) by means of this system engineering tool will be demonstrated as a sample for validating results. © 2010 by ASME.
Mirshams m., M. ,
Taei, H. ,
Novinzadeh, A. ,
Haghi, H. ,
Rezvani, V. ,
Sajjadi, N. ,
Nahvi, A. ,
Haddadi, A. ,
Roshanian, J. ,
Nikkhah, A.A. Publication Date: 2009
9pp. 7233-7239
The dynamics and control of satellite have been widely studied, because of their technological significance. There are many tools to observe or examine spacecraft control laws and one of the most common of them is simulation. Simulation has been used for educating students and users, too. Many solutions exist to the problem of simulating the functional space environment, for example: underwater test tanks, magnetic suspension systems and also air-bearings. Spherical air-bearings have been used for spacecraft attitude determination and control hardware verification and software development for nearly 50 years, because they provide frictionless environment and unrestricted motion. In spherical air bearings, pressurized air passes through holes in the grounded section of bearing (cup) and establishes a thin film that supports the weight of sphere. The purpose of this article is to describe a laboratory-based test-bed that will be used to explore various issues and concepts in spacecraft dynamics and control. The main components of this facility are spherical air-bearing, three-axial sensor, battery, on-board processor and three reaction wheels. All of these subsystems have been designed and manufactured by our team in Space Research Lab., because of some limitations in preparing them from foreign companies.
University of Isfahan
Address: Isfahan, Azadi Square, University of Isfahan
