The adaptive wall tunnel T’3 was built by ONERA as the pilot facility for the cryogenic, transonic, pressurized tunnel T2 of ONERA located in Toulouse and it has now been relocated at VKI. It has stainless steel walls with a 5 mm thickness of internal cork insulation for cryogenic operation.  The original insulated test section is 100 mm wide, 600 mm long and 117 mm high at inlet with flexible top and bottom walls.  Although originally designed at ONERA for transonic operation (11400 RPM fan speed, 125 kW mechanical power, Mach 0.8, 4 bar pressure, 120 K temperature with liquid nitrogen injection), it is being used at VKI under ambient conditions with a 7.5 kW motor, yielding Mach 0.23 (80 m/s) in the test section.

A new VKI-developed test section is available, with increased length (800 mm) and flexibility (130 mm total deflection) for increased streamlining capability.  A method based on the Cauchy integral technique is available to obtain interference-free test conditions on airfoils up to 200 mm chord length at Reynolds numbers between 2 x 105 and 1 x 106.

Both test sections are equipped with multiple pressure taps on top and bottom walls. Pressure acquisition through scanning valves is performed using specific data reduction and wall adjustment programs.

The von Karman Institute for Fluid Dynamics has converted its Cold Wind Tunnel CWT-1 into an icing wind tunnel. This facility was designed in the past to study the motion of films of anti-icing fluids applied to aircraft wings during a simulated take-off. Built out of wood and epoxy-fiberglass composite, it is internally insulated with a 5 cm layer of polystyrene foam covered by a smooth epoxy lining. It runs in a closed-loop configuration and it has a 1.6 m long test section with a 0.1 m x 0.3 m cross section. In order to provide optical access, both the top, side and bottom walls of the test section are made of double glazing. The large size of the windows in the test section allows several optical devices (e.g. ILIDS, PDA, 2D profile measurements, high speed imaging,…)  to be installed at the same time, but since the windows are interchangeable, a non-transparent insert can be fitted to house samples and or other instruments, e.g., a force balance. The large dimensions of the window in the test section allow installing several optical devices simultaneously. The CWT-1 is driven by a 12kW motor and it can achieve maximum flow velocities of 70 m/s within seconds. A honeycomb is located after the centrifugal fan in order to ensure flow uniformity. The cooling of the facility is achieved by the injection of pressurized liquid nitrogen through six spray nozzles located in the return circuit. When liquid nitrogen is injected at a pressure of 5bar, temperatures as low as -40°C can be reached at full speed. Without the use of nitrogen nozzles, the flow of the wind tunnel can be by-passed through a cooler enabling temperatures ranging from  -5°C at low speed to +5°C at maximum speed. The temperature and the pressure in the wind tunnel are measured by a thermocouple and a pressure probe located at the beginning of the test section. In addition, a hygrometer registers the humidity inside the wind tunnel.

The CWT-1 has several water injection points upstream the test section. The water is injected into the wind tunnel with low pressure by a plain-orifice insulated nozzle and it breaks into droplets by the effect of the air velocity inside the wind tunnel. The diameter of the nozzle orifice can be selected according to the water flow that needs to be injected. Currently, the CWT-1 is able to operate with supercooled liquid droplets and mixed phase conditions. Further modifications aim at operating under glaciated conditions using a spray bar system in the settling chamber.

VKI CWT-1 summary

- Minimum temperature; -40^°C
- Maximum speed: 70m/s
- Maximum run time: 30 minutes
- LWC: 0.001-1g/m³ - MVD: 10um-300um
- 6 component balance
- Particle Image Velocimety
- High speed imaging
- Interferometric Laser Imaging and Droplets and Ice Crystal Sizing
- Global Rainbow Thermometry

Contact

Jeroen van Beeck
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Phone: +32 2 359 96 78

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.

The L-6 facility is a low speed, open circuit wind tunnel for the study of plane mixing layers. The wind tunnel is divided into two parts over its entire length by a splitter plate, which originates at the exit of the duct from the two fans and has sharp trailing edge with a wedge angle of 1.2º at the contraction exit.  The two-dimensional contraction ratio is 6:1. The spanwise length is 0.3 m and the test section where the mixing layer develops has a cross-section of 0.3 m x 0.2 m.  Velocity can range from 1 to 20 m/s.

The wind tunnel has been adapted to the study of turbulence modification induced by particulate laden flow.  To create the two-phase flow, an ultrasonic spray nozzle produces tiny droplets with a very small initial momentum in one of the air streams.  Advanced measurements techniques such as Phase Doppler Anemometry, Particle Image Velocimetry and Particle Tracking Velocimetry and Sizing can be accommodated.

The wind tunnel may also be equipped with several interchangeable rectangular test sections placed at the exit of the left jet.  These test sections allow the investigation of internal two-phase flows, and in particular of particles / vortices interaction, within various geometries, including cavities.