PURPOSE: To obtain a low-noise secondary air stream with a compact apparatus by providing a first nozzle for blowing a main air stream, providing a second nozzle for blowing the secondary air stream around the first nozzle, and providing hole parts for the secondary stream in a wind tunnel duct at the upstream side.
CONSTITUTION: Double nozzle 10 for a wind tunnel comprise a first nozzle 12 for blowing a main air stream M and a slit shaped second nozzle 14 which is provided around the first nozzle 12. Opening parts 18 for taking air for a secondary air streams S are provided at the wind tunnel duct 16 on the upstream side of the nozzle 12. The opening parts are communicated to the nozzle 14 through a flow path 20. A pressure P16 at the inside of the duct 16 at the upstream side of the nozzle 12 is higher than a pressure P12 at the blowing-out part. Therefore, the air for the secondary air stream can be readily taken. Thus, it is not necessary to provide a blower and the like separately. The sound of the air for the secondary stream S is already silenced in the duct 16. Therefore, it is not necessary to otherwise provide a muffler device. Thus, the low-noise secondary air stream can be obtained with the compact apparatus.
TAKEI KUNIMITSU
IKEDA MAKOTO
