The invention relates to closed-circuit tunnels used for aerodynamic researches, sportsmen-parachutists training and other purposes. The inventive closed-circuit tunnel comprises a confuser, a working area, a diffuser, one or several return channels, a blower unit and turning bends having different flow deflection angle, wherein the bend having the smaller flow deflection angle is placed in a high-speed flow cross-section, whereas the bend having the greater flow deflection angle is arranged in a low flow speed cross-section. In a preferred embodiment, the tunnel comprises a first turning bend containing one turning gut for turning the airflow at 60 degrees, a second turning bend containing two turning guts for turning the airflow at 120 degrees, and a third turning bend containing three turning guts for turning the airflow at 180 degrees. The invention makes it possible to reduce air pressure losses, the drive power and a specific amount of metal per structure.
1. A return-flow wind tunnel comprising
a confuser,
a test section,
at least one diffuser,
at least one return channel,
a blower unit, and
at least two turning bends including a first turning bend and a second turning bend,
wherein said confuser, test section, at least one diffuser, at least one return channel, blower unit, and at least two turning bends being interconnected in a closed loop, and at least the first turning bend and the second turning bend having different airflow turning angles and arranged so that the turning bend with a minor airflow turning angle is installed in the section with larger airflow velocity, and the turning bend with a larger airflow turning angle is installed in the section with lesser airflow velocity.
2. The wind tunnel according to claim 1 , wherein
said at least two turning bends including a third turning bend,
each of the turning bends comprising
at least one turning gut, designed so that the first turning bend containing one turning gut for turning the airflow at 60 degrees, the second turning bend containing two turning guts for turning the airflow at 120 degrees, and the third turning bend containing three turning guts for turning the airflow at 180 degrees.