Blockage effect induced by an airfoil model in the low-velocity wind tunnel test section
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DOI: 10.1134/S0869864320030051
Blockage effect induced by an airfoil model in the low-velocity wind tunnel test section * V.I. Kornilov and A.N. Popkov Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia E-mail: [email protected], [email protected] (Received October 30, 2019; revised October 30, 2019; accepted for publication November 6, 2019) The results of computational and experimental studies of the flow around a symmetric airfoil with a relative thickness of 12% in the free stream and in a low-velocity wind tunnel with a closed test section are presented. The experiments are performed for the Reynolds number Rec = 0.7·106–2·107 and angles of attack α = –12°÷ 12°. The problem is
numerically solved in a 2D formulation by using the ANSYS Fluent software package. The mathematical model of the flow includes steady Reynolds equations closed by different turbulence models, including the k-ω SST model, which is a superposition of the k-ε and k-ω models. A significant effect of blockage of the wind tunnel test section with limited dimensions by the airfoil on the flow character and aerodynamic characteristics of the airfoil even if the blockage coefficient is only 5.7% is demonstrated. Keywords: airfoil, blockage, wind tunnel, pressure, aerodynamic characteristics.
Introduction Determination of loads acting on the model and the pressure distribution on the model surface is an important aspect of wind tunnel (WT) tests at the stage of the development of almost all flying vehicles. At the same time, the experience described in [1–3] and many other publications shows that the coefficients of aerodynamic forces and moments, as well as the surface pressure distributions measured in the WT in most cases differ from the corresponding values in the unbounded flow conditions. The problem is not only incomplete simulation of the Reynolds number in WT tests, though the influence of this criterion on the aerodynamic coefficients can be fairly significant [4]; these differences are largely caused by the relationship between the model size and the WT test section dimensions, model configuration, WT structure (open or closed type), and other factors. Moreover, an extremely important problem associated with the transposition of WT test results to real flight conditions is not considered here. Another important aspect at this stage of research is that the flow around a flying *
This work was performed within the framework of the Program of Fundamental Research of the State Academies of Sciences in 2013–2020 (Project Nos. АААА-А17-117030610137-0 and 0323-2018-0005) and was supported by the Collective Use Center “Mechanics.” V.I. Kornilov and A.N. Popkov, 2020
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V.I. Kornilov and A.N. Popkov
vehicle in the WT can differ from the flow around a corresponding geometrically similar body in an unbounded flow even if the Reynolds numbers are identical. In an incompressible flow, this difference is associated with the presence either of the jet boundary (in the WT with an open test section)
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