The wind can affect tall buildings, which is why these structures are designed in a certain way that makes them safe in the occurrence of strong winds.
When a strong wind blows, buildings tend to sway and create a slight rocking motion as if you were on a boat sailing on smooth waters. This is how wind primarily affects tall buildings.
In turn, do tall buildings have an effect on the wind? Do they make it windier or block wind? You’ll find out in this article!
Here’s How Tall Buildings Affect The Wind:
Tall buildings can either block the wind or make their surrounding area windier. They can either cause the wind to speed up, slow down, or change directions. This all depends on the height, size, shape, and orientation of the building, plus the direction and speed of the wind.
Here are some examples of how tall buildings affect the wind:
1. Tall Buildings Can Cause Wind Tunneling
Also known as wind channeling, wind tunneling is the phenomenon wherein the wind is channeled through the gaps between buildings. This creates strong wind currents and sometimes, turbulent wind.
Wind tunneling is produced when the wind and a tall building interacts.
When the wind blows in the direction of a tall building, it is either forced to go around it, over it, or through any gaps between buildings. And if the gaps are too narrow, the wind can be squeezed and it will accelerate. This, in turn, will create a fast-moving channel of wind.
Wind tunneling is a great example of how tall buildings can make it windier. The shape of the building can largely affect this phenomenon.
Tall buildings with rough exterior walls or irregular shapes tend to create more turbulence, stronger wind currents, and less consistent wind channels compared to buildings with smooth exterior walls.
Wind tunneling can be both good and bad. In some cases, wind tunneling can be used to generate wind energy, such as in wind turbines. This is especially useful in urban areas that harness wind to become more energy-efficient.
However, wind tunneling can also be dangerous, especially if the current is too strong. Wind and sudden changes in its direction and speed can blow large debris and cause accidents on the streets.
2. Tall Buildings Can Cause Vortices
This is another example of how tall buildings can make it windier.
Vortices are swirling currents of wind that are created by the interaction between the wind and a tall building.
When the wind blows in the direction of a tall building, it creates a wake on the sheltered side of the building, where the wind is slowed down and distributed. This creates an area of low pressure causing the air to spin and create vortices.
Tall buildings with irregular shapes or sharp corners are more prone to create vortices and more turbulent wakes. On the other hand, buildings with flat surfaces or rounded corners create less turbulence.
Just like wind tunneling, vortices can be used to generate wind energy.
Vortices can have negative effects too. This wind effect can create hazardous conditions for pedestrians and aircraft.
Vortices creating strong gusts of wind can knock out pedestrians or blow large debris causing accidents. And when an aircraft flies through vortices, they can experience turbulence and sudden changes in altitude, which can be dangerous.
3. Tall Buildings Can Cause Updrafts And Downdrafts
Updrafts are vertical currents of air that move upward, while downdrafts are vertical currents of air that move downward. Both can be caused when wind interacts with a tall building.
When the wind blows in the direction of a tall building, it is forced to either go around, over, or through it. It can create an area of high and low pressure, and depending on the pressure difference, the air may rise or sink. This creates updrafts or downdrafts.
In this example, a tall building may either block the wind or make it windier.
Updrafts occur when air is forced to rise over a tall building. This can happen when the building has a sloping or curved shape that causes the wind to be deflected upward. In this case, the building blocks the wind by forcing it to go upward.
This is beneficial when updrafts can be harnessed to generate wind energy. At the same time, it prevents the surrounding area of the building from becoming windier.
On the other hand, downdrafts occur on the sheltered side of a tall building. The wind is slowed down here and creates an area of low pressure, causing it to sink and create a downdraft. In this case, the building makes it windier in its surrounding area.
This can be dangerous for pedestrians as they can get knocked out by strong gusts of wind caused by downdrafts, especially when the wind changes speed and direction abruptly. The wind can also blow large debris, which can cause accidents on the streets.
If a tall building has a flat surface and rounded corners, then it can help block the wind effectively and create a more consistent wind flow and less turbulence.
4. Tall Buildings Can Create Wind Shear
Wind shear is the phenomenon wherein the wind suddenly changes in direction or speed over a short distance.
This phenomenon is caused when the wind interacts with a tall building. In this example, a tall building can either make it windier or block wind.
The wind is forced to either go around, over, or through the building. When it goes around the building, it creates an area of high and low pressure which causes the wind to change direction or speed.
When a tall building creates a wind shear wherein the wind slows down and suddenly changes directions, it blocks the wind from creating strong gusts in the surrounding area.
This happens, particularly when the building has a smooth surface with a round shape or if it has more rounded corners.
If a building has sharp corners and an irregular shape, it can create a wind shear wherein the wind suddenly changes speed. This can create strong, and sometimes, turbulent winds. This effect makes it windier and it can be dangerous for pedestrians when it causes accidents.
Related: How Do Tall Buildings Affect Wind And Tornados: 7 Important Facts
5. Tall Buildings Can Contribute To The Heat Island Effect
The heat island effect is the phenomenon where urban areas become significantly warmer compared to rural areas. This phenomenon can be caused by tall buildings.
Tall buildings can contribute to the heat island effect because of the materials used to build them.
Many buildings are made from concrete and asphalt, which absorb and store heat from the sun. The heat is then released into the air and this is what makes urban areas extremely hot, especially during summer.
Tall buildings can also create canyons of air that trap heat at street level. This also reduces air circulation, which causes higher temperatures in the building’s surrounding area.
Can You Know Beforehand If Tall Buildings Enforce Or Block Wind?
It may be hard to tell beforehand if tall buildings enforce or block wind because it can depend on several environmental factors such as the speed and direction of wind.
However, how a building is designed can be a good way of knowing how it will affect the wind. The height, shape, size, and orientation of the building have varying effects on the wind.
In general, tall buildings with flat and smooth surfaces and rounded corners can create a more consistent wind flow and less turbulence. They may even cause the wind to go in a different direction, thus blocking them.
Meanwhile, buildings with irregular shapes, rough surfaces, and sharp corners tend to create more turbulence and stronger air currents, thus making the surrounding area windier.
Designing Tall Buildings For Wind
The Science Of Wind Tunnels – Where And Why Those Harsh Winds Strike
Vortex Shedding And Wind Load Analysis Of Tall Buildings