In the present work, an analytical study is proposed to investigate the flutter behavior of low-aspect-ratio wings in subsonic flow. An equivalent plate model is used for structural modelling of a semi-monocoque main wing, consisting of ribs, skins, and spars. Legendre polynomials are used in the Rayleigh-Ritz method as trial functions, and the first-order shear deformation theory is utilized to formulate the structural deformation. Boundary conditions are enforced by applying proper artificial springs. A doublet point method is used to calculate the unsteady aerodynamic loads. Chordwise pressure coefficient distribution at the tip and root of a rectangular wing oscillating in pitching motion is calculated. Flutter analysis is performed using the k method. Instead of using the computationally expensive finite element method, the proposed approach is intended to achieve purposes of quick modelling and effective analysis in free vibration and flutter analyses of low-aspect-ratio wings for preliminary design applications. The effects of aspect ratio on the flutter behavior of wings in subsonic flow are investigated. The obtained results are validated with the results available in the literature. تفاصيل المقالة

To ensure the correct design and proper operation of turbine engine components, various types of ground tests must be performed, which requires the simulation of the input flow to these components. To test hot components such as nozzles, it is necessary to create a hot flow, which is done by the preheat system of the inlet flow. For the ground test of the nozzle of a turbofan engine that has an afterburner in addition to the combustion chamber, the preheat system must be able to supply air in two modes, dry mode and reheat mode. In this paper a combustion chamber with an afterburner is used to provide hot air to the nozzle. In the first step, using experimental and analytical relations, the combustion chamber is designed. The presented algorithm has the ability to calculate the diameter and reference surface of the combustion chamber, components of the combustion chamber and thermodynamic parameters. Then the obtained results are compared with the data of a similar annular combustion chamber. The comparison indicates the acceptable convergence of the design results with the experimental results. Finally, the output flow of the combustion chamber is considered as the input of the afterburner, and the temperature of the combustion flow is increased by the afterburner to the desired temperature. In addition to the ability to design a V-gutter flame keeper, the afterburner design algorithm also calculates the thermodynamic characteristics of the afterburner output stream, considering the requirements of flame stability. تفاصيل المقالة