This work describes a lumped parameter mathematical model for the prediction of transients in an aerodynamic circuit of a transonic wind tunnel. Control actions to properly handle those perturbations are also assessed. The tunnel circuit technology is up to date and incorporates a novel feature: high-enthalpy air injection to extend the tunnels Reynolds number capability. The model solves the equations of continuity, energy and momentum and defines density, internal energy and mass flow as the basic parameters in the aerodynamic study as well as Mach number, stagnation pressure and stagnation temperature, all referred to test section conditions, as the main control variables. The tunnel circuit response to control actions and the stability of the flow are numerically investigated. Initially, for validation purposes, the code was applied to the AWT ("Altitude Wind Tunnel" of NASA-Lewis). In the sequel, the Brazilian transonic wind tunnel was investigated, with all the main control systems modeled, including injection
The main objective of the present work is to study the mass extraction in a transonic wind tunnel. The strategy consists in the analysis of the flow in the test section, with special attention devoted to the slots. To this end the results of tests of a NACA 0012 airfoil are presented. Besides, the influence of the returning flaps and forced evacuation compressors upon the results were also assessed. The experimental investigation used both the classical staticpressure taps as well as the ''Pressure Sensitive Paint'' (PSP) techniques. The PSP complete pack includes the devices to apply the special ink, dedicated computer codes, and the electronic equipments necessary in the usage of the technique. This technique permits the measurement of the static pressure along all the surface of the body, and further allowed for the observation of shock waves. To complete the study, the flow inside the test section is also numerically simulated. In overall terms the tunnel stream, the pressure distribution on the airfoil and the flow through the slots are investigated. Values of pressure on the surface of the foil were compared including here the present experimental and numerical results, plus data from the literature what guarantees the proper accuracy of all the investigation performed.
Injectors are to be installed in a transonic wind tunnel with the ultimate objective of expanding the Reynolds number envelope. The aim of this research effort is to numerically simulate the steady mixing process involving the supersonic jets and the tunnel subsonic main stream. A three-dimensional, Reynolds-averaged Navier–Stokes numerical code was developed following the main lines of the finite-difference diagonal algorithm, and turbulence effects are accounted for through the use of the Spalart and Allmaras one-equation scheme. This paper focuses on the “design point” of the tunnel, which establishes (among other specifications) that the static pressures of both streams at the entrance of the injection chamber are equal. Three points are worth noting. The first is related to the numerical strategy that was introduced in order to mimic the real physical process in the entire circuit of the tunnel. The second corresponds to the solution per se of the three-dimensional mixing between several supersonic streams and the subsonic main flow. The third is the calculation of the “engineering” parameters, that is, the injection loss factor, gain, and efficiency. Many interesting physical aspects are discussed, and among them, the formation of three-dimensional shocks’ and expansions’ “domes”
The present study has the purpose of presenting a numerical and experimental analysis of the flow patterns on the fore-body section of a sounding rocket model in the transonic regime. The measurements were carried out in the Pilot Transonic Wind Tunnel, known as TTP, at the Instituto de Aeronáutica e Espaço (IAE), in São José dos Campos, Brazil, for Mach numbers ranging from 0.6 to 1.06 and zero angle of attack. The experimental techniques of pressure taps, pressure-sensitive paint (PSP) and schlieren visualization method were performed on a 1:34 scaled model of a sounding rocket. Complex phenomena as shock waves, boundary layer detachment, and expansion waves were clearly identified from the PSP pressure field and from the schlieren images. Good agreements between the PSP, pressure taps and numerical simulation results were observed, except around the tip of the model because of the curvature and also in details that were not captured by the camera.
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