This article was taken from the
October 2012 Issue of Wired magazine. Be the first to read Wired's
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Ever wondered how your car would
hold up in a hurricane? In physics labs, scientists can test the
force of air in giant wind tunnels on everything from Formula One
cars to oil rigs. Life-sized tunnels are hard to build in your
garage, but "the principles are the same for all wind tunnels --
it's just scale," says Clive Evans, founder of Scale Engineering, a
company that makes models for testing.
1. Aim for a top
The main component is the fan. To be able to make any valid
measurements of air force, you need an air speed of at least 30m/s,
according to Durham University wind-tunnel scientist David
Sims-Williams. "Find a fan with a performance datasheet."
2. Build from
At one end you need a broad, conical nozzle, which
you can make from plywood. This funnels air into a Perspex tube.
The section then broadens out until it meets a diffuser, behind
which is the fan. Stick the components together with masking
3. Become an instant
Low-speed Wind Tunnel Testing by Barlow, Rae and Pope is
"the wind-tunnel bible", according to Sims-Williams. It will help
you determine the ratio of lengths and area that can improve your
wind tunnel's shape for greater efficiency.
4. Scale it down
There's no point trying to test a real car in your wind tunnel.
Realistically, says Sims-Williams, a 300mm by 300mm model is the
largest that would fit. "A six-per-cent scale model, such as a
toy car, would work well for your experiment."