What is Wind Tunnel Testing?
Aircraft manufacturers do something pretty magical – they create flying machines built from the most advanced materials available in which we can travel to any corner of the world. But how do they do it?
To answer this question, we go back in time over 100 years to the dawn of modern aviation at the beginning of the 20th century…
The World's First Modern Aeroplane
The world’s first modern aeroplane was designed and built by the Wright brothers in 1903; it was a glider propelled by two propellers each powered by a lightweight engine.
The Wrights built the glider first and learnt how to control it by flying it as a kite and then as a glider. They then designed and built the propellers and engines.
Critical to their success was their successful wing design and for this they used a wind tunnel which they designed and built themselves.
The Wright Wind Tunnel
The Wrights had over 200 wing designs they wanted to try out quickly without having to build a full scale glider for each design – so they decided to use a wind tunnel.
A wind tunnel works by blowing air past a model of a wing or an aeroplane so that the designers can measure the aerodynamic performance of the model and compare the merits of different designs.
The advantage of a wind tunnel is that you can test a model in complete safety and at much less expense than building a full scale aeroplane.
While modern wind tunnels have become much larger and more powerful, the principle they use is the same. The designers build a model of an aeroplane, install it in a wind tunnel, blow air past it and measure the aerodynamic performance. They can then compare the merits of different designs and answer questions such as which design is more aerodynamic or which is easier to control.
The most important measurements for the Wrights were lift which keeps the aeroplane in the air and drag which is the air resistance the propellers and engines must overcome.
The photograph shows the wind tunnel built by the Wright brothers in 1901; the fan and flow straightening vanes are visible. On top of the tunnel at the far end is a viewing window through which the experiments could be observed.
Computational Aerodynamics
The advent of computers is a comparatively recent technological development which is becoming increasingly important in how aeroplanes are designed.
Computers can now be used as a virtual wind tunnel to simulate the air flowing past an aeroplane. Designers can get much more detailed information about the air flow from a computer model; but even the most powerful of today’s computers can only roughly approximate the full complexity of how air flows around an aeroplane. In addition, a computer simulation can take several hours or even days to run - whereas wind tunnel data for the same case can be acquired in less than a second.
So wind tunnels remain a vital part of the modern aircraft design process because they enable aircraft companies to check their computer generated data and ensure that their designs are safe.
