Description: The main factors that affect the test results quantitatively are the criteria for the perfection of the wind tunnel, namely the level of initial turbulence ε and the coefficient of the field of the working part of the tube μ. Periodic inspection of the wind tun-nel, its parameters and criteria of perfection of the wind tunnel is a necessary condition for Research of aircraft models in wind tunnels. The aim of this work is experemental determination of the values of the criteria for the perfection of low subsonic speeds T-1 wind tunnels of the Ivan Kozhedub Kharkiv National Air Force University in preparation for testing the models of wings with terminal aerodynamic surfaces. The paper presents the results of the experimental determination of the values of the initial level of turbulence ε and the coefficient of the field of the working part of the tube μ of the T-1 wind tunnel at low subsonic speeds T-1 of the Ivan Kozhedub Kharkov National Air Force University. To determine the initial turbulence ε, which quantitatively influ-ences the aerodynamic characteristics of the tested models, the property of the sensitivity of the ball to turbulence was used in the T-1 wind tunnel. As the flow velocity in the wind tunnel increases from the minimum, the laminar boundary layer on the sphere becomes turbulent, with the separation point shifted back and the drag coefficient decreases. We use the assumption that this transition occurs instantaneously at a certain Reкр number, called the critical and corresponding value of the coefficient of drag of the ball CХа=0,3. From the dependence and the relationship between the critical Reynolds number (Reкр=290000) and the level of pulsations, it is established that the initial turbulence of the flow in the working part of the wind tunnel T-1 is ɛ=0,45 %. An important parameter characterizing wind tunnels is the degree of uniformity of the air flow in the working part (the core of the flow) of the pipe. It is known that in the core of the flow the deviation of the velocity head should not exceed ± 2 % of the mean value. The graphs of the change in the field coefficient for the three sections of the working part of the T-1 wind tunnel, which are obtained as a result of the processing of the experimental data, are presented in the work. The coefficient of the field of the working part of the wind tunnel T-1 KhNUPS μ=1,00247, the deviation from the control point is =0,2 %. The conclusion is made that the test conditions in the T-1 wind tunnel correspond to the normal conditions that are established for aerodynamic complexes, which ensures high reliability of the obtained results of aerodynamic studies.
Keywords: wind tunnel, initial turbulence, field coefficient, critical Reynolds number