SMART BLADE has considerable experience in industrial wind tunnel testing. Industrial or Research Wind Tunnels however are generally extremely expensive, bulky and very complicated. For academic, educational and demonstration purposes a small, robust, reliable and low cost wind tunnel is required. In order to demonstrate some basic principles of wind tunnel testing, the research team of SMART BLADE designed and constructed the "Small Visualisation Wind Tunnel". It is an affordable, low turbulence, low noise, portable wind tunnel, ideal for flow mechanics' lectures as well as for general eye-catching demonstrations.

The visualization wind tunnel was designed based on the established closed-loop wind tunnel principle. The general design was based on analytical state of the art calculations while the final dimensions were decided after several numerical flow simulations with in-house CFD tools. The flow visualisation is generated with water particles (produced with an Ultrasonic Humidifier) and turned into streamlines with the hot-wire technique. The test models are built from laminated, precisely cut, foam blocks and their angle is adjusted through a digital servo system.

The fan used in the SMART BLADE wind tunnel is an axial 100W - 24V (DC) unit. It has an efficient blade design which provides silent and smooth operation. The precise speed variability of the fan (0-2750 min^-1) allow for a very fine flow velocity regulation inside the wind tunnel. At the standard wind tunnel version the velocity at the test section can be regulated between 1 - 12 m/s. The low free stream velocities are required for smooth and clear flow visualization while the higher velocities are necessary for aerodynamic force measurements.

The test section of the wind tunnel comprises a measurement box which has a large opening on one side for easy access and unobstructed view. The measurement box is internally covered with non-reflecting material which provides a good contrast and a suitable background for flow visualization. The opening of the measurement box is covered by a glass, to remove any external flows that might influence the flow visualization results.

SMART BLADE can provide laminated test wings of some basic types of airfoils or CNC machined test wings of any airfoils type or any other desirable shape. The test wings are attached on a rotating mounting system which allows their easy replacement. The mounting system is driven by a digital servo which can vary the Angle of Attack (AoA) of the test wing. The digital servo be controlled manually, can operate is automatic loops or can be externally controlled through a computer (USB port) via the existing servo controller.

The test section is also equipped with a heated lateral grid which generates the necessary streamlines out of the uniform "fog" of water particles. The heating power of the grid can be regulated from the user thus regulating the thickness of the generated streamlines. Another flow fine tunning possibility is provided to the user in the form of a manually adjustable back-pressure flap. This device regulates the cross-section of the tunnel just before the axial fan thus allowing the user to fine-tune the free-stream velocity.

The low turbulence levels of the SMART BLADE wind tunnel in combination with the effective flow visualization concept and the dynamic test wing control provide many interesting possibilities for experimental investigations. The manual precise AoA adjustment permits the demonstration of several flow phenomena such as:

- Upstream & Downstream streamline deflection

- Trailing edge stall

- Boundary layer flow reversal

- Leading edge stall & Vortex bursting

- Laminar separation

- Karman Vorticex Streets

- Wake roll-up

- Magnus effect

- Nozzle & Diffuser flow visualization

- Vehicle profile flow visualization