Abstract

Watch out! Eddies and vortexes are powerful regions of air and water flow that you have to watch out for in some surprising places. Try out this science fair project to discover why they can be dangerous, as well as where and how to find them.

Objective

To detect and measure the turbulent airflow around test structures.

Introduction

When you get a new piece of furniture, you have to figure out where to put it. You want your room to look nice, but at the same time, you want to make sure traffic can flow easily in and out of the room, and that the room functions as it was intended. For example, if the room is a play space, there must be enough room to spread out toys and games. If the room is a living space, seating must be arranged so people can easily talk to one another.

Environmental engineers—the people who decide where to place or site a wind generator—have a similar task. They want to avoid blocking views or creating noise pollution with the wind generators, and at the same time, they want the generators to function as well as they possibly can for the given location. They want this machine that changes the free energy found in wind forces into electrical power, to do the best job it can of making power, which requires consideration of factors like:

• Cost
• Aesthetics (beauty)
• Zoning laws
• Noise pollution
• Wind speeds
• Wind turbulence
• Surrounding structures
• Topography
• Installation
• Transportation
• Wind generator type (horizontal-axis or vertical-axis)
• Environmental conditions (extreme cold or heat)
• Access to a power grid, and
• Mechanical stresses.

For a wind generator to work effectively, it needs a location that has average winds of at least 10-13 miles per hour, or better, for over a year. A good location is also free from "bad winds" that can damage the wind generator, such as turbulent or chaotic winds that change quickly in force, speed, and direction.

The power the wind generator is able to produce increases by the cube of the wind speed. Cube means multiplying the wind speed by itself twice. Therefore, a small increase in wind speed results in a large increase in the power that the wind generator can produce. If you raise the wind generator up to as high as is allowed by building rules, you can take advantage of higher wind velocities. The trade-offs, though, are possible obstruction of views, difficulty in installation and transport, and mechanical stresses and fatigue from high winds, which can cause the wind generator to fail.

In this project, you will focus on two of the factors used in siting a wind generator: wind turbulence and surrounding structures. You might have heard the word turbulence before if you've flown on an airplane close to a storm. The pilot might have come on the intercom system and cautioned the passengers to remain seated and buckled because the plane was expected to experience some "rough air" or turbulence.

Turbulence is chaotic, random changes in the flow of a fluid or gas. An example is the behavior of smoke rising from a birthday candle, or the motion of frothy, white waves around the hull of a speedboat. Turbulence creates eddies (in the case of liquids, like water) or vortices (in the case of gases, like air). In eddies or vortices (which is the plural of vortex), the flow of the liquid or gas is reversed. An ideal place to spot an eddy in a river is on the downstream side of a rock or other obstacle in the river.

Just as eddies occur on the downstream side of a rock in a river, vortices occur on the downwind side of a building or obstacle. This is why airplanes cannot take off too close together. Wake turbulence develops behind a plane as it takes off, which churns up the air downwind, making wind conditions too dangerous for the next plane, so air traffic controllers wait 2-3 minutes, depending on the size of the planes, before allowing the next one to take off. This gives time for the turbulence to disappear.

When siting wind generators, environmental engineers try to avoid placing generators downwind of structures or obstacles because of wind turbulence on the downwind side of the structure. Turbulent wind is not an efficient way to generate power and the violent, changing winds can also damage the wind generator. In this science fair project, you'll detect wind turbulence behind a structure by observing the motion of a streamer. You'll also determine how far away you need to be from the structure for the turbulence to die down.

Terms and Concepts

• Environmental engineer
• Site
• Wind generator
• Wind turbulence
• Topography
• Chaos
• Cube
• Velocity
• Random
• Eddy
• Vortex
• Downwind
• Wake turbulence

Questions

• Why is it important to avoid turbulence?
• Where can you find turbulence?
• How can you avoid turbulence?

Materials and Equipment

• Streamer, such as party streamer, a piece of old cassette tape, or a strand of plastic tape from a pom-pom; streamer should be several inches long
• Slender stick or pole, at least 2 feet long
• Fan
• Boxes (3 of equal size), approximately 6.5 inches x 5 inches x 2.5 inches; examples of this size are boxes of pasta or salt. The boxes don't have to be empty, but first ask your parents if it is OK to use the boxes if they are full.
• Rocks, a few handfuls to use as weights if the boxes are empty
• Measuring tape
• Room that is free from drafts
• Lab notebook

Experimental Procedure

Variations

Careers

If you like this project, you might enjoy exploring these related careers:

Related Links

• Science Fair Project Guide
• Other Ideas Like This
• Environmental Engineering Project Ideas
• My Favorites

Cite This Page

General citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.

MLA Style

APA Style