Wind tunnels are widely used in science and in the sports world. Yet computer simulations that simulate wind electronically are also becoming more and more common. Are wind tunnels still advancing, or will they be wholly replaced by computer-generated wind in the future? Professor Bert Blocken, who specializes in aerodynamics, casts some light on the current status of the wind tunnel and its future.

We can’t ignore it: Wind tunnels have proven their relevance time and time again. They are used to gain insight into how wind affects tall buildings, racing cars and large groups of cyclists. The wind tunnel in Eindhoven, for example, played a role in breaking the world marathon record set by Kenyan Eliud Kipchoge, who was the first to run a marathon under two hours last October.

The name says as much: In these wind tunnels, all kinds of objects are exposed to air currents just above the earth’s surface. That way, the effects of strong gusts of wind can be recreated. It’s crucial to carry out this research in order to be able to guarantee, for example, the safety of skyscrapers. In the world of sports, the tunnel is used to measure the effect of the wind on materials worn by athletes. Like skaters’ clothing, for instance.

Wind force 12

The four fans in the wind tunnel in Eindhoven are capable of producing a wind speed of up to wind force 12. This means that they can blow at speeds of up to 33 meters per second. The tunnel is built in the shape of a ring, so that the air is given a fresh boost after each cycle. This model makes the tunnel a lot more energy efficient compared to a linear tunnel.

Professor Bert Blocken © TU/Eindhoven

Dutch technical universities make full use of wind tunnels. Eindhoven University of Technology (TU/e) has a 46-meter-long wind tunnel. Blocken was involved in its construction: “There were already plans for a tunnel at TU/e back in the 1970s. But the costs are considerable. You can’t just set it down anywhere.” Nevertheless, a few years ago Blocken was asked to work on the construction of a new tunnel, which was finally built in 2017.

The wind tunnel in Eindhoven is very special. Although there are huge tunnels in use all over the world where even complete trucks and fighter jets are being tested at full scale, the size of the Eindhoven tunnel is quite impressive. The measurement section of the tunnel is 27 meters long, 2 meters high and 3 meters wide. Large enough to accommodate an entire team of cyclists. “There are few tunnels of this type that reach this length,” Blocken says. Additionally, the tunnel specializes in simulating air currents such as those just above the earth’s surface. This enables us to recreate “real life” situations.

Tall buildings

And it is not just in Eindhoven where they are specialized in aerodynamic research. There is plenty of research into wind currents in their own tunnels at Delft University of Technology as well as at the University of Twente (UT). The wind in the UT tunnel can reach speeds of up to 240 kilometers per hour.

According to Blocken, The Netherlands is definitely in the Top 10 when it comes to research in aerodynamics. This high ranking is easy to explain from a historical perspective, in Blocken’s view. Wind blows hard in the Netherlands and we always have to face the consequences of this. “For example, The Netherlands has always had to be protected from the sea and from storm surges”.

That The Netherlands attaches great importance to wind can also be seen in the fact that it is the only country in the world that has set standards to prevent wind threats to tall buildings. In 2006, these standards were included in what is known as the “NEN8100.” This aims to protect architects, municipalities and project developers from wind disruption. “And after 13 years, The Netherlands is still the only country with this kind of standard,” Blocken states.

Wind tunnels versus computer simulations

Besides wind tunnels, computer-based wind simulations are also being used more and more frequently. Software is used to calculate the influence of air resistance on objects. Blocken also works with these wind simulations on a regular basis. “They provide a lot more information in comparison to wind tunnels. Whereas the wind tunnel often only yields one or just a few values, for example the drag of a cyclist, the computer simulations provide a lot more detailed information.”

As a consequence, simulations are very useful in wind research and are being used more and more often. Nevertheless, they also have major limitations. This is even the case with the most advanced computers, according to Blocken. “Suppose five new helmets are tested for cyclists. This only takes 15 minutes when it’s done in a wind tunnel. If that needs to be simulated accurately by a computer, then you’ll be busy with that for about two weeks.”

Apart from that, the development of wind tunnels hasn’t stood still either. Although they may still look the same as they did about 60 years ago, considerable progress has been made. “For example, the measuring equipment has become a lot more accurate and many processes have been automated.” The fans have also improved. ” Whereas they used to be made of magnesium, now they’re made of stainless steel. ” Blocken concedes, “Close to Brussels, there’s still a wind tunnel in operation that’s about 65 years old. ”

Irreplaceable

Despite the fact that wind tunnels have been in use for quite some time now, they are still widely used and are irreplaceable even to this day. In fact, according to Blocken, physical tunnels and computer simulations go hand in hand. Both can add something to wind research. “We carry out wind tunnel measurements and computer simulations independently of each other and compare the results of both methods. You then have more certainty.” Wind tunnels will therefore not fall into neglect in the coming years. “They’re still going to be built one hundred years from now. You simply can’t live without them.”