Wild Winds: Turbulent Flow around Structures

A windy science project from Science Buddies

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Energy-efficient: What sort of breeze makes wind turbines spin best? Learn how engineers pick the best places to generate wind energy in this fun science activity. Hold on to your hat!

Key conceptsWind power

Introduction

Background

The same thing happens in air when wind blows around a tall structure, such as a building or a tree. This is an important factor to consider when placing wind turbines, because they will generate the most power from steady winds that blow in the same direction. Inconsistent, turbulent flow can decrease power output or even damage the turbines. In this project you will use cardboard boxes to represent "buildings" and see how they affect the flow of "wind" blowing from a fan.

Of course, turbulent flow in air is much harder for us to see than a turbulent stream! Sometimes scientists do controlled experiments using colored smoke to observe airflow. In this project you will use a streamer tied to the end of a stick to visualize the airflow.

Materials

• Fan
• Stick or rod, a few feet long
• Streamer, a few inches long
• Cardboard box (The size of the box depends on the size of your fan—the larger the fan, the larger the box. If the box is empty, you might need to put something inside it to weigh it down.)

Preparation

• Set up the cardboard box a few feet from the fan, with the fan pointed at the box.
• Tie the streamer to the end of the stick.

Procedure

• Turn the fan on.
• Standing to the side so your body does not interfere with the airflow, use the stick to hold the streamer "upwind" of the box (on the side of the box facing the fan).
• Now move the streamer to the "downwind" side of the box (on the side of the box facing away from the fan) but hold it fairly close to the box.
• Gradually move the streamer farther and farther away from the box on the downwind side.
• Extra: See how your results change if you change the speed of the fan.
• Extra: Try the same activity with different size boxes.
• Extra: Try the activity with different or irregularly shaped objects, such as furniture or houseplants.
• Extra: Take your stick and streamer outside on a windy day. Determine which way the wind is blowing and find large objects such as buildings or trees to test the airflow.

Observations and results

This is important when placing wind turbines because they should not be too close to large buildings on the "downwind" side. The buildings will create turbulent flow, which will decrease the performance of the wind turbines.

More to exploreWild Winds: Detecting Turbulence around Structures, from Science BuddiesWhitewater Rafting by Rasheed, Kohner, Scotty and JB, from PBS KidsWind Turbines, from Explain That StuffScience Activities for All Ages!, from Science Buddies

Science Buddies

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