HYPERSONIC WIND TUNNEL

HYPERSONICS AT HOME

This project was intended to be a simplified version of a hypersonic testing facility and allow for high-speed aerodynamics to be tested at the hobbyist level. This setup is designed to use hardware store materials and be safe enough (with the proper PPE) to do in a garage. However, this project still involves compressed gasses, high voltage, and a vacuum chamber so build at your own risk.

for more explanation, see video: https://youtu.be/m0ScVG0Y6t4?si=OIimpATVGbWDaNR0

DESIGN

HOW IT WORKED

This wind tunnel operates the same way as a rocket engine, using a convergent-divergent nozzle with a high expansion ratio to accelerate air to over mach 5. The air is supplied by a standard household air compressor at 150 PSI and is stored in the air chamber before the test. The vacuum pump removes most of the air in the vacuum chamber, increasing the pressure differential and allowing the gasses passing through the nozzle to expand fully. When the button is pressed, the solenoid valve and high voltage source are turned on, causing the high pressure air to get superheated in the arc plasma and accelerated by the nozzle. The air reaches speeds over mach 5 and cools rapidly as it expands, being exhausted into the vacuum chamber. The whole test is over in less than half a second.

HOW DO YOU SEE SHOCKWAVES?

Seeing shockwaves can tell a lot about what's going on at high speed - and is the main mechanism used to visualize a test in this wind tunnel. To do this, I used a technique known as schlieren imaging (technically a shadowgraph if no knife edge is used) where sudden density changes such as shockwaves can be observed as dark lines around a profile. I used a concave telescope mirror and a cell phone to accomplish this, but a high speed camera and external light source would get much higher detail, both chronologically and in resolution.

if you want to build a shockwave visualizer for yourself, see video: https://youtu.be/piGYryly5Bw?si=Y6vRp31ZXRJ03kZh and download 3D model: https://www.thingiverse.com/thing:6915073