Several new systematic methods for high fidelity and reliability calculation of static and single dynamic derivatives are proposed in this paper. Angle of attack step response is used to obtain static derivative directly; then translation acceleration dynamic derivative and rotary dynamic derivative can be calculated by employing the step response motion of rate of the angle of attack and unsteady motion of pitching angular velocity step response, respectively. Longitudinal stability derivative calculations of SACCON UCAV are taken as test cases for validation. Numerical results of all cases achieve good agreement with reference values or experiments data from wind tunnel, which indicate that the proposed methods can be considered as new tools in the process of design and production of advanced aircrafts for their high efficiency and precision.
An inlet grille typically needs to be installed at the inlet of the air intake of the ventilation-and-cooling system embedded in airborne electronic equipment to improve pneumatic stealth performance. Here, a typical flying wing model is used as a case study, and a computational fluid dynamics (CFD) simulation is performed. The flow resistance characteristics of the air intake of the opening of the ventilation-and-cooling system on a flat fuselage surface with and without an inlet grille are analyzed at different flow rates and Mach 0.25. The effects of the grille opening shape, diversion angle, thickness, aperture size, and hole shape on the flow resistance characteristics are investigated in detail. The grille is found to effectively guide airflow entry: although the flow resistance at the inlet is increased, the flow resistance at the inlet and outlet of the air intake is significantly reduced. The optimal developments of the outflow and flow resistance characteristics are obtained for a quadrilateral opening. The smaller the diversion angle is, the smoother the airflow entry, and the higher the quality of the internal airflow. The rectification, viscous resistance, and weight exhibit opposing trends with increasing thickness and must be comprehensively considered in designing an optimal scheme. A large-aperture grille ensures good flow patency at low flow rates, whereas a small-aperture grille can reduce flow perturbations and separation at high flow rates by smoothly guiding air into the intake. A grille with round holes has a better spanwise and chordwise balancing effect on the airflow and better flow resistance characteristics than a grille with diamond-shaped holes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.