The aim of this article is to propose methods for obtaining the aerodynamic characteristics of a flying object in a turbulent atmosphere. This article presents static aerodynamic characteristics of an unmanned aerial vehicle (UAV), which have been obtained during experimental examinations and during numerical calculations. The results have been compared with each other in order to validate the numerical model and methods. The method for modeling gusts using state-of-the-art CFD software (i.e., ANSYS Fluent Release 16.2) has been proposed and applied to obtain the aerodynamic characteristics of a UAV including during gusts. Two cases have been analyzed. In the first case, a downburst was modeled. In the second case, a single oblique gust was modeled (i.e., changing the angle of attack and the angle of sideslip), that had a complicated time course in regard to its velocity. Although this article is focused on the assessment of the vulnerability of a UAV model to gusts, the practical implications of the proposed methodology are applicable to a wide selection of objects, including wind turbines.

This paper presents a numerical analysis of the stability of the flow parameters along the intake duct of an aircraft jet turbine engine. This problem has been investigated by many research teams and was included in the literature analysis. The unstable operation of a turbojet intake system can be the consequence of many adverse factors, including an intake vortex. The investigated intake system, due to its low location to the plane of the airport, is highly susceptible to the formation of an intake vortex. The phenomenon of an intake vortex can, in the worst-case scenario, result in the surging of the turbojet, and even engine stalling. This paper presents a developed model of the forward section of an aircraft, complete with its intake duct, and the method of its discretization. The intake-system model and numerical analysis were performed in Ansys Fluent. The flow parameters adopted for numerical simulations, under specific boundary conditions, corresponded to the operating conditions of the engine cooperating with the investigated intake system. The numerical calculations were performed assuming an air-pressure rise in the end section of the engine-intake system, reflecting the reduction in the pitch angle of the inlet stator blades of the fan. As a result, the pressure distributions in a significant cross section in the intake system were obtained. The results were analyzed with the quantitative distribution of the pressure fields by applying a dimensionless potential-pressure ratio. The pressure ratio enabled a comparative analysis of the nonuniformity of the total-pressure distribution in selected cross sections of the intake system. The results were revealing in terms of growing unstable flows in the flow duct. A major conclusion drawn from the results, by testing the dimensionless potential-pressure ratio, was that, within certain limits, it was possible to improve the flow uniformity by increasing the throttling pressure.

Impact of the Intake Vortex on the Stability of the Turbine Jet Engine Intake System

The article presents the study of the turbulence model’s influence on aerodynamic characteristics of a cruise missile model obtained during numerical calculations conducted using ANSYS Fluent Release 2023R1 software. Three turbulence models (i.e. Spalart-Allmaras, realizable k-ε and SST k-ω), as well as three computational meshes with a different refinement in a boundary layer region, were investigated. The results were analyzed and compared to characteristics obtained experimentally in the low-speed aerodynamic tunnel at the Military University of Technology (Warsaw, Poland).

This study provides the results of experimental tests of the effect of floats on the aerodynamic characteristics of the “OSA” plane in an asymmetric flow. The tests were carried out in a low-speed wind tunnel owned by Institute of Aviation Technology, Faculty of Mechatronics, Armament and Aerospace (FMAA), Military University of Technology (MUT, Warsaw, Poland).. The model of “OSA” was tested at dynamic pressure q = 500 Pa within the range of slip angles β = -2828. The tests were carried out for the plane model in the so-called “plain” configuration, i.e. at non-deflected control surfaces and wing mechanisation elements. The model was tested in two variants – with floats and without floats. The effect of deflection of the flaps, ailerons and rudder on the aerodynamic characteristics of the test model was also examined. The obtained values of drag coefficient, lateral force coefficient and yawing moment coefficient are presented in the form of tables and graphs. The tests showed that the floats had a significant impact on the curves of the characteristics. They result in a considerable increase of the value of the drag coefficient and in a deterioration of weathercock stability.