What Are Venturi Tunnels In F1? (Venturi Effect Explained)

One of the terms you’ll hear a lot in the era of ground effect F1 cars is the Venturi effect and Venturi tunnels. It might sound complicated and confusing, but once you understand the concept, you’ll see why Venturi tunnels are so important to the 2022 Formula 1 cars.

Venturi tunnels on F1 cars are cutouts under the car that generate downforce by accelerating air underneath them, creating an area of low pressure, due to the Venturi effect. The effect is almost like the cars are being sucked towards the ground, while generating minimal dirty air behind them.

The Venturi effect is important to understand as it is one of the primary ways that F1 cars produce downforce from 2022 onward. Below, we go through what Venturi tunnels are in basic terms, while doing our best to make it as easy to understand as possible.

What Is The Venturi Effect In F1?

In order to understand the Venturi effect in Formula 1 we need to look at how it is applied in a practical sense. The Venturi effect is used in other elements in the real world as well, and while it has existed in F1 in various forms for many years, it has now been brought back in a big way to make the ground effect more effective (more on that later).

Understanding the Venturi effect in full is complicated, and it’s taught at universities the world over as a key component of science and engineering degrees. However, to put it simply, the Venturi effect is perceived as the increase in speed of a fluid (like air) as it goes through a constricted area, which also results in a decrease in pressure.

An Example With A Pipe

If we use a pipe as an example, we can clearly see how the Venturi effect is at play. In order to create the Venturi effect, there needs to be a constriction in the pipe, creating a sideways hourglass shape. As the liquid or gas (both called a fluid here) flows through this bottleneck, the speed of the flow increases, and the pressure drops.

The reason the air speeds up is to do with Bernoulli’s principle and the continuity equation, which we won’t go into too much detail on here. Essentially, what goes in one end of the pipe has to come out the other, and the only way that can happen when the pipe is narrowed is if the fluid speeds up through the constriction.

But there’s also the law of conservation of energy at play, which means the energy (not just the mass) that goes in one side has to equal that which comes out at the other side. The faster moving air has more kinetic energy, and so to balance this, the pressure decreases.

The Venturi effect was discovered by Italian physicist Giovanni Battista Venturi in the 18th century. To truly understand the Venturi effect involves words and equations that we don’t need to consider for this simple explanation, and instead we just need to consider the implications of the Venturi effect on an F1 car.

The Example Of A Wing

If we forget the pipe example and this time consider the front wing of an F1 car, we can imagine the air coming towards the wing before being “split” in two. Some of the air goes over the top of the wing, and some of the air goes underneath it. Much like in our pipe example, the front wing of an F1 car creates an area of constriction, which leads to downforce.

However, it does this in a slightly different way to the pipe. The constriction in the case of a front wing is very much instantaneous. Right when the air interacts with the front part of the wing, it is squeezed underneath it. It then accelerates, reducing the pressure under the wing. The higher pressure air above the wing pushes down on the lower pressure area below it, creating downforce.

Essentially, the air going over the top of the wing moves at a slower speed as it runs into resistance as a result of the wing’s upwardly sloping shape. This slow moving air can be thought of as “bunching up” and therefore creating an area of denser air, which creates an area of high pressure pushing down on the wing.

Underneath the wing, the air is accelerated, and this leads to a less dense section of air under the wing, creating an area of low pressure. The net result is that the area of high pressure above the wing pushes down on the area of low pressure under the wing, resulting in what we call downforce.

We’ll discuss how the Venturi effect contributes to the ground effect in a later section, but for now the essentials to remember are:

• Air moves faster when it is constricted
• Faster moving air creates an area of low pressure
• There’s an area of higher pressure air above a wing
• There’s an area of lower pressure air below (and behind) a wing
• The high-low pressure difference results in downforce being generated

How Has The Venturi Effect Been Used In Formula 1?

The Venturi effect has always had a place in Formula 1. However, the Venturi effect has largely had its place in the form of front wings that generate downforce, whereas the cars for 2022 and onward make far more use of the Venturi effect underneath the car – which the previous generation did to a lesser extent – which we’ll discuss shortly. However, ground effect cars haven’t been seen since the 1980s.

``Note: The ground effect itself has long been an integral part of downforce production in F1, but ground effect cars - those with notable Venturi tunnels in their floors - were outlawed in the 1980s.``

Dirty Air

In the last few decades of Formula 1, teams have made use of a lot of over body downforce, using large, complex wings and bargeboards, along with other components, to keep them stuck to the track in the corners. But this method of producing downforce has had a massive impact on the ability of cars to follow each other closely.

This is because there is a wake of turbulent air thrown out the back of the car and to the sides through various outwash-generating components, which is detrimental to the ability of a following car to produce downforce. This is called “dirty air” and it has plagued modern F1 cars for decades. Therefore, cars have been losing grip whenever they are close to another one, making overtaking extremely difficult.

The Return Of The Ground Effect

It was decided that in order to promote better racing, the cars need to produce cleaner, and less turbulent air in their wake, which allows the following cars to get much closer and have a better chance at overtaking, as their downforce producing components – wings and underfloor Venturi tunnels – are less hindered. But what are Venturi tunnels on F1 cars?

What Are Venturi Tunnels In F1?

Venturi tunnels on F1 cars are sections carved into the floor of the car, creating a constricted area under the car through which air is accelerated. This accelerated air creates an area of low pressure, and this effectively creates a suction effect under the car, generating downforce.

This means that the “tunnels” in the floor of the car will have a wide opening at the front in order to catch a given volume of air. They will then begin to narrow and constrict, which will increase the speed of the airflow underneath the car, decreasing the pressure underneath it as well.

``Note: It's not about getting as much air as possible under the car, but rather being able to manipulate a given volume of air in specific ways that are conducive to producing the desired aerodynamic effects for a given car's design.``

At the rear of the car, the tunnels have a wide opening once again, where a diffuser gradually allows the high speed air to lose some of its momentum. This gives off far less turbulent air at the back of the car than using over body downforce alone, meaning trailing cars don’t lose as much of their downforce and they can follow closer through the corners.

Diffusers Didn’t Solve The Problem

The diffusers were already there on the cars from 2021, and for many years before that. They are not solely responsible for the decrease in the amount or severity of the dirty air that comes off the back of the current generation of cars. There were many other components that were tweaked or removed to decrease the turbulence that makes it hard for cars to follow each other.

The 2022 rules put a lot of focus on reducing the vortices and outwash produced by the front wing, bargeboards and brake ducts. This is why some parts of the cars now look a lot simpler than they did in 2021, with the absence of various turning vanes and other complex aerodynamic components on the bargeboards and front wings.

So, it’s not that the diffuser and the Venturi effect have reduced the dirty air that comes off the back of the cars, but the rules have forced the teams to rely less on complex over body/vortex-focused aerodynamic devices that were so common in the previous generation of cars (with some components and techniques being outlawed altogether). This meant more of a focus was put on Venturis and diffusers.

How Does This Help Fix The Overtaking Problem?

A lot of the air is now forced underneath the car in order to make use of these Venturi tunnels. However, teams now have the ability to kick the turbulent air higher up by using something called a beam wing. Doing so will create what is known as the mushroom effect, and it will kick most of the turbulent air over the following car, which will create a space of clean air right behind the lead car.

However, this space is not completely clean air, as there will still be some turbulent air coming off the wake of the lead car. The nature of the diffusers and Venturi tunnels mean that there is not only a low pressure area under the car (generating downforce through the ground effect) but also an area of low pressure behind the car.

Getting Out Of The Dirty Air

While not a massive area of low pressure, it’s still going to be noticeable for a car directly behind another one. This means that cars will find more downforce slightly off line to the lead car. In previous generations of cars, this area is where the wake of the lead car was often the worst, leading to a massive loss in downforce when slightly behind and to the side of the lead car.

Instead, cars now have more downforce and grip in a prime overtaking position, right behind the lead car where they can also benefit from a slipstream effect. However, to really understand why this is important, how it works, and even just why the Venturi tunnels are being used in F1, it’s worth considering the ground effect in more detail.

How Does The Ground Effect Work In F1?

We have previously seen the ground effect being used in Formula 1 in the late 1970s and early 1980s. It was first introduced by Lotus, and the Venturi effect gave them more downforce than their wings did, with the real major advantage being that underfloor tunnels come with a minimal drag penalty.

It wasn’t completely straightforward though, as the Lotus 78 was set up in a way that resulted in a lot of the downforce being generated too far forward. To balance this, the team had to run large, draggy rear wings. This made the Lotus 78 slower on the straights, but the team managed to correct things in the Lotus 79, which was far less draggy but still balanced.

While massive front and rear wings can provide lots of downforce, as we’ve described above, through the high pressure above the wing and low pressure below the wing, they also create a fairly big area of low pressure behind them.

The more aggressively curved a wing is, and in other words the steeper it is shaped, the more downforce it can generate. This is because there is a massive difference in air pressure above and below the wing. This big pressure difference equals massive downforce. However, the steeper the wing the larger the low pressure area behind it, as well as underneath it.

A Visualization Of Drag

A simple way to think of it is by imagining you stick your hand out the window of a moving car (as a passenger, obviously). If you have the palm of your hand facing the ground, you won’t feel too much of the air pushing against it.

However, if you then rotate your hand to have your palm facing the direction in which the car is travelling (i.e. forwards), you’ll feel like your hand is being pushed backwards. This is not a result of the wind as many people think, but it’s actually because your steeply angled hand is slowing down the air molecules that hit it straight on.

As we know from earlier, slow moving air molecules create an area of high pressure. Some of the air goes around your hand, and moves much faster, creating an area of low pressure right behind your hand. This big difference in air pressure causes the high air pressure to “push” against your hand, in the direction of the area of low pressure behind it.

Pulling You Back

This effect is called drag, and it’s why you feel like your hand wants to go flying backwards. The exact same thing happens with wings on F1 cars, only they’re not angled quite so steeply, but they are often traveling at upwards of 150 mph through the corners!

So, while these wings create a lot of downforce, they also create a lot of drag. So, not only is there an area of dirty, turbulent air behind the wake of the cars, but there is also an area of low pressure trying to “pull” the car backwards. This results in a loss of top speed on the straights.

So, while the Venturi tunnels and ground effect minimize the dirty air given off at the back of the car, they also don’t come with as much of a drag penalty as massive front and rear wings do. This allows the cars to make up for some of the downforce lost as a result of regulations reducing the size and complexity of the wings on the cars.

Wings Are Essential

But we can’t simply throw away the idea of front and rear wings entirely on F1 cars. They are still responsible for a lot of the downforce modern F1 cars generate. They are used in tandem with the ground effect rather than just using wings on their own for the reason of minimizing dirty air and making following cars easier.

But they are also necessary as the ground effect on its own cannot be used to generate all of the downforce the cars need for their massive cornering speeds. The reason for this is that the rules limit how effective the ground effect can be, albeit indirectly through various dimension restrictions (the ground effect could definitely be used to generate all the car’s downforce if the rules allowed it).

To understand how and why the rules affect this, we must look to the past. But before we go back to the 1970s, it’s worth noting that the underfloor has always been key in F1.

The Floor Has Always Been Important

While the new cars do look drastically different, both above and below the floors, teams have been making use of the Venturi effect underneath the cars through the floors and diffusers for decades. In the early 2000s teams made up to 40% of their downforce this way, and that jumped to about 65% by 2018. But teams had to get creative to do this.

In order to seal the air under the car’s floor, which had to be flat (i.e. no complex Venturi tunnels like the current generation of cars), teams would use complex bargeboards and sidepod undercuts to push air away from the floor and to downwash air under the floor for downforce production.

They also created outwash around the front wheel areas, to create and strengthen vortices that helped seal the floor. This all had the effect of making for effective, floor-centric downforce production.

These tactics mimicked the skirts used on the cars in the 1970s and 1980s (see below), but the complex bargeboards (and many other complexities of the previous generation of cars) were banned for the 2022 season, which led to the reintroduction of the Venturi tunnels under the cars. But how are things different this time around when compared with the ground effect cars of the past?

How Is F1’s Ground Effect Different This Time?

In the 1970s and early 1980s the cars used massive side skirts in order to maximize the Venturi effect under the car. All of the cars had these skirts that covered the sides of their cars, and it dramatically increased the Venturi effect underneath the car by not allowing any of the air flow under the car to escape out the sides.

This basically sealed off the underfloor of the car, leading to a massive improvement in downforce levels. To put it simply, it meant teams could create an even bigger pressure difference between the air under the car and the air above and to the sides of the car, which translated into much more downforce.

The Skirt Problem

However, the problem was that these skirts were being damaged throughout the race either through contact with other cars or simply by riding kerbs too aggressively. A broken or damaged side skirt would result in a breaking of the seal, which could effectively destroy the car’s downforce, making the driver instantly lose control.

Formula 1 has learned from its past mistakes, and instead of bringing back the side skirts they only allow teams to create the Venturi effect by using vanes and underfloor tunnels. This reduces the risk of the cars losing their downforce from damage sustained throughout the race.

The turning vanes and their designs can get fairly complex, but their overall purpose is to improve airflow under the car and seal the floor edges, and they do this by creating outwash and vortices. This leads to a similar effect the skirts had, but without the skirts.

But in order to change the aerobalance of the car for optimal performance, front and rear wings remain a necessity in F1. The golden formula is basically to allow the cars to generate lots of downforce with minimal drag and while producing minimal dirty air. However, in practice, there are always ways teams will play with this formula to suit them and hinder those behind them!

How Modern F1 Car Floors Work

Finally, let’s take a closer look at the workings of the floors on modern F1 cars to better understand what’s actually going on when we combine everything we’ve discussed above. The floor on a modern F1 car has many different parts and there are lots of outwash-generating and vortex-creating components, but one of the main mechanisms at play involves the inlet area and the channel area.

Air Flows In

Air flows under the car and into the narrow inlet section, and when it leaves this area, it expands laterally, and this draws in more air, which produces downforce as a result of the air speeding up at the beginning of this area of lateral expansion. The airflow is carefully managed through the design of the car, as more air is not necessarily better here.

The Throat Area

Air then flows towards the ‘throat’ of the Venturi channel, where the tunnel constricts again at the lowest point of the car’s floor. This is where the air experiences the most acceleration and reaches its highest speed, which correlates with the lowest pressure as a result of the Venturi effect (which leads to a lot of downforce being produced in this area).

Entering The Diffuser

Where the throat ends and the diffuser begins is often referred to as the ‘nozzle’ area, as it’s where the air rapidly expands to fill the large diffuser volume, similar to water coming out the nozzle of a hose after being constricted in a pipe. There is a large difference in pressure between the ambient air behind the diffuser and the lower pressure air at the throat.

This sucks more air through the Venturi channels for downforce production, and the diffuser is designed to smoothly bring this air back to the ambient pressure. If it happened in a rapid, uncontrolled manner, there could be flow separation and stalling, which would result in a loss of downforce. This is why there is a lot of focus on the diffuser when designing an F1 car.

Final Thoughts

Venturi tunnels are cutouts in the bottom of F1 cars’ floors that are used to generate downforce. This promotes a concept known as the ground effect. This effectively allows F1 cars to create a vacuum underneath them that pulls the car down into the tarmac, giving them more grip.