Articles
Nasiri d., ,
Adami m., ,
Taei, H.,
Parhizkar h., 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. 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.
