SCHLIEREN APPARATUS FOR AF302

A monochrome Schlieren apparatus for use with the Continuous Supersonic Wind Tunnel (AF302).

The Schlieren apparatus allows students to see density gradients as variations in intensity of illumination. This allows them to see supersonic air flow patterns around models. It also clearly shows shockwaves and expansions, and students can compare their positions and angles with values predicted by theory.

The focused light from the light source (and condenser lens) passes through the optical slit and is reflected at 90 degrees to the first achromatic lens. The light passes through the working section of the wind tunnel, then through the second achromatic lens. A second mirror reflects the light at 90 degrees towards the Schlieren edge. The Schlieren edge enhances the light refracted image. The small lens focuses this image onto the imaging screen. Achromatic lenses are chosen because of their ability to pass light without colour distortion, that would normally ruin the Schlieren image.

The apparatus includes digital imaging equipment to record the images.

The video monitor is useful to display the images to groups of students. The imaging equipment can capture still images and any real-time changes in the image.