Armfield - Advanced Fluid Mechanics - C15 Computer Controlled Subsonic Wind Tunnel

The C15 is a small wind tunnel designed for benchtop operation. Air is drawn through the working section by a variable-speed fan at the discharge end of the tunnel.

A honeycomb flow straightener is incorporated at the inlet, and a 9.4:1 contraction ratio ensures well developed airflow through the working section.

The working section is fabricated from clear acrylic to give good visibility of the models, and appropriate model connection points are included in the side wall and roof of the working section.

A unique feature of the working section is that its entire base is removable to allow the insertion of large or complex models such as the C15-24 Bernoulli Apparatus, C15-25 Boundary Layer Plate or alternative models constructed by the user.

The basic wind tunnel is supplied with a USB interface to enable it to be controlled from a PC (not supplied). An electronic pressure sensor mounted in the wall of the working section measures the static pressure, allowing the air velocity to be calculated and displayed on the computer.

A manometer bank is required for use with the optional models and instruments. Two options are available, a 13-tube water manometer or a 16-channel electronic manometer.

With the electronic manometer the readings and data logging are integrated with the wind tunnel operational software. With the water manometer the readings can still be integrated and recorded, but need to be entered into the computer manually.

The optional models are mounted through a circular hatch (120mm diameter), the models being permanently mounted on a hatch cover to seal the opening (flush with the inside wall of the working section to avoid disturbing the flow). They are secured by quick-release clamps on the side wall of the working section. Where necessary the hatches incorporate an angular scale enabling the model to be manually rotated to known angles.

A plain, clear acrylic cover is supplied for applications where no model is fitted, but this may be adapted by the user to mount alternative models.

A second, smaller hatch behind the model mounting position allows the optional Wake Survey Rake (C15-15) to be installed downstream of the various optional models. A plain hatch cover is installed until this option is fitted.

The working section incorporates a simple technique for flow visualisation around any of the optional models. A lightweight twine follows the flow contour around the model and shows if and where boundary layer separation (breakaway) occurs. A simple adjustment arrangement enables the length of twine and its vertical and horizontal position to be easily varied.

Three tappings in the roof of the working section, each with a blanking plug flush with the inside wall, allow the flow visualisation system or the Pitot static tube (option C15-14) to be inserted. These tappings are located at the start of the working section, upstream and downstream of the model mounting position.