Aeronautical and Space-Rocket Engineering
Аuthors
1*, 2**, 1***1. Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia
2. Moscow Institute of Physics and Technology (State University) (MIPT), 16, Gagarin St., Zhukovsky,140180, Russia
*e-mail: m_brut@mail.ru
**e-mail: yetun53@gmail.com
***e-mail: olga.v.pavlenko@yandex.ru
Abstract
Thermodynamic state of the atmosphere is being defined by the spatial distributions of such parameters as temperature, pressure, density, humidity, air turbulence etc. As a rule, the aircraft aerodynamic characteristics computing conditions are being set in accordance with the standard atmosphere, in which data for the dry air is presented. In reality, atmospheric air consists typically of dry air and water vapor mixture. The humid air parameters frequently differ from the standard values, which should be accounted for when the aerodynamic force acting on an aircraft computing, since this fact may under certain conditions affect drastically the final result and, as a consequence, the flight safety.
It is quite clear that in real conditions weather conditions affect the aircraft flow-around. Flight safety has enhanced, and the number of aviation accidents associated with the adverse weather conditions has reduced due to the aviation technology development, as well as airfield, aircraft and meteorological equipment improvement. Nevertheless, not all meteorological issues of the aircraft flight safety ensuring have been completely resolved. As of today, a real possibility of studying the environmental properties effect on the aircraft aerodynamic characteristics become real with the CFD methods development.
The article presents the results of parametric numerical studies of the water vapor percentage composition in the air impact on the aerodynamic characteristics and a wing mechanized profile flow-around specifics in both cruising and takeoff and landing configurations.
Computations were performed in dry and wet air, which represents the mixture of dry air with water vapor. With the volume content of water vapor increase, the air mixture density, its viscosity, and the Reynolds number of air mixture decrease.
Computations demonstrated the lift force increase, the drag reduction and aerodynamic quality enhancing at the humidity increase. It was found that the basic humidity impact on the takeoff-and-landing characteristics was associated with the development of flow-separation phenomenon on the flap.
The article demonstrates that the larger the separation zone, the stronger the relative effect of the air humidity on the aerodynamic characteristics of the mechanized wing profile. The presence of the water vapor in the air affects the separation zone so that when humidity in the air increases, the separation point position of the boundary layer on the flap shifts to its trailing edge. This phenomenon is explained by the fact that with the air humidity increase, the tangential stress on the flap surface increases as well. Consequently, the separation zone size decreases and, as a result, the lift force increases.
It should be noted herewith that the percentage composition of water vapor in the air affects most significantly on the drag.
The air humidity increase affects the separation zone and reduces its size. The larger the size of the separated backflow area, the stronger the relative effect of the humidity.
Keywords:
mechanized wing profile, aerodynamic characteristics, air humidity, CFD methodsReferences
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