I make the tunnel from a piece of poster laminate sourced from our school library. You could get a piece from anywhere that laminates posters. Get a piece that has been run through the laminator so that it is clear and stronger. I tape the edges together to make a cylinder. Punch a few holes around the top edge and tie on some string. I hang this end from the ceiling.
Next I put an electric fan, face up on the table under the cylinder. I like to put the fan in the non-rotate mode and then inside a basket to stop it wobbling around on the table. You will need to hold the wind tunnel to keep it steady while the fan is turned on. The children quickly get the hang of it.
Turn it on and watch the children scour the room for items that will soar up the wind tunnel. Feathers from our collage trolley are always the first thing they head for. Tissues are also popular. Someone always tries to send a wooden block up the tunnel.
After a day or so of experimenting, someone usually comes up with the idea of making a small parachute. This year for the first time, I have a few children making hot air balloons (made from a balloon and a little cup).
This is a very popular investigation and the excitement of the first few items sailing up the tunnel are always met with little squeals of delight. The excitement is contagious and the learning engagement is fantastic.