Low Speed Mini Wind Tunnel L-7 to L-13
The L-7 facility is a low speed, open circuit, miniature wind tunnel, with blowing fan, used for laboratory training in boundary layer and three-dimensional velocity measurements. It is specially designed to be of economical construction, to require minimal floor space, and to be easily transportable. The facility is comprised of a centrifugal fan, driven by a 700 W, variable-speed AC motor, a wide angle diffuser fitted with screens, a settling chamber fitted with a honeycomb and a 9:1 contraction. Several test sections, with 0.16 m x 0.16 m cross section and lengths up to 1 m are available. Maximum flow speed is 20 m/s, with a turbulence level of about 0.3 %.
The L-10, L-11, L-12 and L-13 are four identical facilities, of similar design to the L-7; each having a smaller contraction ratio (5.76:1), a larger test section of 0.2 m x 0.2 m, and a maximum speed of 15 m/s. They are used mainly for laboratory training in several fields, including boundary layers, convective heat transfer, flow in cavities, and the calibration of small instruments.
The L-7+ is a scaled up version using the same design principle, with a 1300 W variable-speed AC motor, a 9:1 contraction, and a 0.36 m x 0.27 m test section with length of 1 m. Maximum speed is 15 m/s, with a turbulence level of about 0.3%. A second test section with the same cross section and a length of 4 m with adjustable side walls to vary the longitudinal pressure gradient is also available. A third test section, with cross section 0.3 m x 0.1 m, length of 2 m, with adjustable top wall and a maximum speed of 20 m/s is also available. This facility is used for laboratory training as well as for studies of turbulent boundary layers over smooth, rough or riblet surfaces with controlled longitudinal pressure gradient.