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Understanding the

Vortex

Cannon

Foundational Theory & How It Works

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Learning Outcomes

Briefly define fluid dynamics - Air pressure
Apply knowledge of fluid dynamics onto the experiment
Create your own mini vortex cannon!

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Learning Outcomes

Briefly define fluid dynamics - Air pressure
Apply knowledge of fluid dynamics onto the experiment
Create your own mini vortex cannon!

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Table of contents

01

02

03

Vortex Rings

Fluid Dynamics

Vortex Cannon

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Fluid Dynamics

01

The Flow of Fluids

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What is Fluid Dynamics?

Fluid Dynamics are the flow of fluids which can be gases or liquids

This can help us understand why the smoke fired out of the cannon is in the shape of a ring

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Vortex Rings

02

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How are they created

Vortex Rings are created when a fluid is forced through a hole

This forces the fluid to curl back in on itself creating the ring shape called a torus

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Visualisation

Check out this video to see the vortex rings

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Vortex Cannon

03

Applying theory & understanding how it works

---------- Forwarded message ---------

From: Matthew Youssef <38204@kristin.school.nz>

Date: Mon, 2 Oct 2023 at 11:15

Subject: Physics Pathfinders

To: <54454@kristin.school.nz>, <43384@kristin.school.nz>, <46663@kristin.school.nz>

Physics Pathfinders

Where have you guys seen a this shape (vortex) before? (water bottle ) liquids and gases are called fluids and can be made into vortexes. This is the condition for fluid dynamics.

Introduction: Vortices in Nature

• Vortices are spinning flows of fluid found in things like water bottles or swirling air.

• Fluids are substances like liquids (water) and gases (air or smoke).

• They follow the rules of fluid dynamics, which is all about how fluids move.

Basic Concepts: Friction, Volume, and Pressure

• Friction: It's like stickiness or roughness when things rub together, making it hard to slide on some surfaces. (Resistance)

• Volume: It's about how much space something takes up, like how much water a glass can hold.

• Force - A push or a pull

• Pressure: It's the push on an area, like when you press your finger on a balloon. More pressing means more pressure.(force)

Understanding Vortices:

• Vortices are everywhere in nature, like tornadoes, whirlpools, or the swirling air behind an airplane wing.

What is a vortex:A vortex is a spinning flow of fluid, like air, water, or smoke, that creates a rotating column or ring of air with a low-pressure core.

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Vortex Cannon Structure:

• A vortex cannon has a cylinder or cone-shaped chamber with one end open and one closed.

• There's a small hole at the closed end, called the nozzle, where air comes out.

How a Vortex Cannon Works:

• When you hit the open end of the vortex cannon with a burst of air, it makes a shockwave inside. (Increase volumeto draw more air in)

• This shockwave travels through the chamber and out of the small hole. (releaed with speed through the hole)

• It drags some air with it, making a spinning ring of air, like a donut that's spinning.

Smoke in a Vortex Cannon:

• When you release the burst of air in a vortex cannon, it pushes the smoke out through a small opening (the hole) between the bottle and the smoke-filled area inside.

• As the smoke is pushed out, it encounters friction along the edges of this opening. Think of it like trying to squeeze toothpaste out of a tube; there's resistance at the tube's opening, and the smoke experiences a similar effect.

• Beyond the initial friction at the hole, there's additional friction where the smoke meets the surrounding, relatively still air.

• This friction acts like a brake, slowing down the smoke as it moves away from the cannon's opening. It's similar to how you might feel resistance when moving your hand through the air, especially if you move it quickly.

• Due to the friction at the edges and with the surrounding air, the smoke is slowed down as it moves away from the cannon's opening.

• However, at the center of the smoke, there's relatively less friction. This is because there's less contact with surfaces and air resistance.

• As a result, the center of the smoke travels faster than the outer edges, creating a spinning motion. This difference in speed between the center and the edges causes the smoke to form a ring shape, as the center moves ahead while the edges lag behind. These edges lagging behind makes them move in a circular mushroom cloud pattern where they get drawn into the fast moving air in the middle utlimtaley forming the ring shape called a torus.

•

• Spinning Around: When the top spins, it pushes things away from the center because it's spinning so fast. That's like when you twirl around and your arms stick out.

• Center Gets Empty: As the top keeps spinning, the very center, where the spinning is happening, becomes kind of empty. It's like a calm spot in the middle of all the spinning.

• Less Pushing: Because there's not much spinning action in the middle, there's also not much pushing happening there. It's like when you play with a toy car, and you push it really hard on one side; the other side doesn't get pushed much.

• Low-Pressure Core: We call this empty, not-so-pushy spot in the middle the "low-pressure core." It's called "low-pressure" because there's not much force or push happening there compared to the outside.

• Stays in the Middle: The low-pressure core stays in the middle as long as the top keeps spinning. Just like how the calm spot in the center of the top stays there while it spins.

Characteristics of Vortex Rings:

• Vortex rings are stable and can travel far.

• They stay in shape because of something called the conservation of angular momentum.

• Vortex rings can also interact with each other, creating cool patterns.

Applications and Demonstrations:

• Vortex cannons can blow out candles from a distance, knock over lightweight things, and show how air moves.

Key Principles:

• Bernoulli's Principle: When air moves quickly through a small hole, its pressure drops, creating a low-pressure core in the vortex.

• Conservation of Angular Momentum: The spinning motion of the air in the vortex is because it's conserving its spinning speed as it moves.

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Materials

Rubber bands
Plastic cup (with hole cut)
Balloon
Smoke (optional)

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Instructions

Cut & and stretch a balloon over one side of a plastic cup
Secure with a rubber band over the edges
Put smoke in the chamber of air (optional)
Pull on the balloon and release!

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Thanks!

For more information find us at

physicspathfinders.org

physicspathfinders@gmail.com

@physics_pathfinders