DIMPLE GENERATOR OF VORTEX STRUCTURES

The paper presents the results of experimental studies of the space-time characteristics of the velocity and pressure field inside a hemispherical dimple on a flat surface. The features of the formation and development of vortex structures generated inside the dimple, as well as their interaction with the streamlined surface of the dimple and the boundary layer were established. Integral, spectral and correlation characteristics of the field of velocity, dynamic and wall pressure fluctuations were obtained. The velocities and directions of transfer of large-scale vortex structures and small-scale vortices inside the dimple were determined. The frequencies of rotations and ejections of large-scale vortices, the frequencies of oscillations of the vortex flow inside the dimple and self-oscillations of the vortex structures of the shear layer, their subharmonics and harmonics of higher orders were established.

Theoretical foundations of increasing the efficiency of wide-angle diffusers and practical results of new solutions to this problem

It is shown theoretically that the efficiency of wide-angle diffusers mainly depends on the method of supplying the working medium to the diffuser channel and on the nature of the interaction of this medium with the subsequent streamlined surface of the diffuser. The first condition is due to those changes in the acting force factors within the wall (boundary layer), which occur during the transition from the inlet confuser channel to the subsequent diffuser, and the second follows from the need to ensure an uninterrupted flow of the working medium moving against the increasing (in the direction of travel) static pressure. The above computational studies of wide-angle diffusers have shown that, subject to theoretically justified conditions, it is possible to ensure uninterrupted flow in flat and conical diffusers with an increase in the opening angle α of their flow path to 20° and with the same degrees of expansion ration to obtain pressure recovery coefficients commensurate with those in diffusers with an angle α = 7°.

Features of Construction and Analysis of Static Accuracy of the Vortex Air Data System of Subsonic Aircraft

The importance of information is noted and the defects of traditional air data systems are described, implementing aerometric, aerodynamic and directional methods using straddled in the fuselage of the air pressure receiver, temperature braking receivers, sensors aerodynamic angles of attack and slip. The features of construction and advantages of the original vortex air data system with one stationary receiver of primary information and frequency-time primary informative signals based on the original vortex sensor of aerodynamic angle and true air velocity with a hole-receiver of static pressure on its streamlined surface associated with the absolute pressure sensor with frequency output are considered. It is noted that according to the results of calculations, the instrumental static errors of the measuring channels of the vortex air data system are close in magnitude to the instrumental errors of traditional air data systems. The reasons are considered, mathematical models and calculated values of methodical static errors of measuring channels of vortex air data system which testify to prospects of application of system on subsonic aircraft are received.