My PBL Project

Introduction

The main purpose of our project is to try to produce smoke rings. We have to use a fog machine and a vortex cannon, or an "air zooka", to shoot out the smoke rings.

In this PBL project, we will be answering these questions and showing you how an "air zooka" works.

Driving Question

What is a vortex cannon/"air zooka" and how is it built? Why does it shoot out smoke rings?

Materials

• air zooka

  • a plastic trash bin

  • trash bag

  • bungee cords or some kind of rope

  • tape

• smoke/fog machine

Procedure

1. Cut the trash bag to where it's a little big bigger than the top of the trash bin, then secure it with a small bungee cord

2. Secure the trash bag to the trash bin by using the duct tape

3. Fill the trash bin with smoke from the fog machine, then smack the end with the trash bag, and the "air zooka" should shoot out smoke rings.

Safety

The smoke from the fog may be harmful to children, so be cautious when doing this experiment, and always have adult supervision when kids are around.

Action Video

Scientific Principle

When the membrane thrusts a burst of air out of the hole, it displaces the surrounding air out side. The surrounding air swirls around in the shape of a twisting doughnut. The twisting doughnut will carry the original burst of air as far as 50 feet away. The physics of moving air is called fluid dynamics. It may seem strange to call air a fluid but motion of gases and liquids are very similar. When a fluid twists or swirls, we call it a vortex. They twist in the shape of a doughnut and the mathematical name for this is called a toroid. Hence our cannon generates toroidal vortices. Vortices are amazing phenomena because the motion of the air is stable and doesn’t require any outside intervention to keep it going. For instance, try blowing a burst of air with your mouth. This is a unstable burst of air that disperses by the time it reaches an arms length. A toroidal vortex on the other hand, will travel all the way across the room. We believe they are formed when the air is mixed with steam or smoke and is forced out of a small circular or cylindrical opening. Because, there is a narrow drag at the surface of the opening, the air in the center is forced to move faster than the air near the opening, ultimately creating a circular motion. In this way, a doughnut like vortex is formed. The shape of the ring is maintained due to the rotational motion of the air that constantly keeps flowing in the vortex ring. In short, a brief explosion in a confined outlet with just the right velocity allows for that impressive “puffs” eventually expanding into an unbelievable ring. It so reveals how nature’s geometric configuration can actually become so sensible and artistic.

Real Life Connection

One case that I think someone would use a vortex cannon in real life would probably be during a concert, show, or party. You could use it for special effects and dramatic smoke. Another way you could use an "air zooka" would be like if you don't like someone, you could shoot them in the face with it. Other more serious ways toroidal vortices are used in real life are dolphins and volcanoes. Dolphins blow perfect air bubble vortex rings too, mostly for amusement. The dolphin will often then examine its creation visually and with sonar. They will sometimes play with the bubbles, distorting the bubble rings, breaking smaller bubble rings off of the original or splitting the original ring into two separate rings using their beak. Besides dolphins, volcanoes can also create huge toroidal vortices. They create smoke rings about 200 meters in diameter, and can go up to 1000 meters high.

Investigation Questions

1. How does the "air zooka" shoot out a ring of smoke?

-when the membrane thrusts a burst of air out of the hole, the smoke is trying to escape in all directions, so the surrounding air swirls around in the shape of a twisting doughnut.

2. How is the vortex cannon built?

-you have to have a plastic trash can or bin with an open end. You then cut a hole on the opposite side of the open end. After that, you cover up the open end with some kind of thin plastic. Then you fill the container with fog then boom, you have a vortex cannon, or "air zooka".

3. Can you shoot out different shapes?

-I don't think so, because the vortex cannon can only shoot out that specific shape, and other shapes wouldn't work or have the same result.

4. Besides humans, what else can produce toroidal vortices?

-dolphins and volcanoes can also produce toroidal vortices.