Improving and processing of weak digital pulse signals using a narrow-band noise structure


DOI: 10.34759/trd-2022-127-09

Аuthors

Khafaga A. S.*, Ilyin A. G.**

Kazan National Research Technical University named after A.N. Tupolev, 10, Karl Marks str., Kazan, 420111, Russia

*e-mail: alisalahelect1985@gmail.com
**e-mail: iag29@yandex.ru

Abstract

The article considers the result of the modernization of strain gauges installed in the working part of the supersonic wind tunnel (AT) ST-3, which allows to increase the range of experimental studies on the angle of attack of the model under study from 0 to 20 degrees. Numerical studies of the flow of the model in the working part of the pipe have been carried out in order to verify that the model is located inside the rhombus of an undisturbed flow.

The supersonic AT ST-3 is widely used to create gas flows of specified parameters for the experimental study of the flow around models of aircraft elements in the range of Mach numbers from 1.5 to 4.2. To increase the range of experimental possibilities, the authors proposed to increase the range of angles of attack of the model under study, taking into account its finding inside the rhombus of a uniform part of the flow.

The supersonic AT ST-3 makes it possible to determine the aerodynamic forces acting on the model under study at angles of attack in the range from — 10° to +10°, which limits the field of study. The range of angles of attack is determined by the boundary of the rhombus of the uniform part of the flow in the working part of the pipe.

To ensure the adequacy of the simulation, the conditions of adhesion and isothermicity were used on the surface of the body and the walls of the working part of the pipe. According to the values of pressure (p0=14 kgf /cm2) and temperature (T0=283K) of the gas in the receiver, the flow parameters in the working part of the pipe were calculated (M∞=4.2; p∞=6467 Pa; T∞=61.8 K; a∞=8 m/s), and also determined the arrangement of the rhombus of the uniform part of the flow.

For the calculations, the Navier-Stokes equations were used, which are closed by the turbulence equations k-ω SST. The calculation scheme is shown in Figure 5. A sphere with a radius of R = 20 mm was chosen as the model.

Modeling was carried out using a structured prismatic finite element grid of 1032 thousand elements (26 elements accounted for the thickness of the boundary layer (parameter y+=0.3)).

Modernization of the fastening system of strain gauges located in the path of the supersonic AT ST-3, taking into account the requirements of permissible «cluttering» of the working part of the pipe, will allow experimental studies to determine the aerodynamic forces acting on the model at angles of attack up to 20°, which is of interest when conducting studies of the aerodynamic spectrum.


Keywords:

phase jumps, phase detector, pulse signals, narrow-band noise, signal-to-noise ratios, noise immunity, narrow band signal (NB), On – Off-Keying Modulation (OOK)

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