PURPOSE:To decrease the noise caused by the jet stream from a nozzle effectively by providing boundary layer controlling mechanisms on the inner wall of a wind tunnel duct at the upstream side of the nozzle. CONSTITUTION:A wind tunnel apparatus includes a nozzle 12 for the wind tunnel and a wind tunnel duct 14 at the upstream side. A plurality of voltex- generator-type boundary-layer controlling mechanisms 18 are arranged on an inner wall surface 16 of the wind tunnel duct 14. The boundary layers in the wind tunnel duct 14 is transformed into the disturbance boundary layer with the voltex-generator-type boundary-layer controlling mechanisms 18 (20, 26 and 32) which are provided on the inner wall surface 16 of the wind tunnel duct 14. The thickness of the boundary layer in the circumferential direction becomes nonuniform. Or the boundary layer becomes thick within the range which does not give large influence on the main stream (an arrow M in the figure 1). The isochrony of each hydrodynamic factor in the boundary layer in the circumferential direction at the inner surface of the nozzle 14 is weakened. Thus, the noise of the jet stream due to shearing stream and the noise of the voltex discharge are decreased.
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