What is the ground effect?

What is ground effect?


The ground effect is one of the bases of motorsport. We show you what it is and how it benefits the performance of the cars.

The aerodynamicists often claim that current competition cars are somehow reverse aircraft. Why? Very briefly, because all the aerodynamic laws applied on a plane, also apply in racing cars. Of course, the aim in both cases is different: in a plane seeks the maximum positive vertical force (upwards) and a car racing the maximum negative vertical force sought (down). In other words: a Boeing 737-800 airflow fail to rise, while Formula 1 is to use it to obtain the maximum grip possible


The operation of ground effect. It is equal to the wing of an airplane In the case of aircraft, the lift and therefore the elevation of the aircraft is achieved based on various laws and principles, among which are the third law Newton (principle of action and reaction), the Coanda effect and Bernoulli’s principle. In the case of cars, provoking aerodynamic laws that extra grip are exactly the same , but applied in reverse.

One particular application of them is known as ” ground effect. ” It was applied for the first time in Formula 1 team Lotus at the age of seventy. The aim was clear:. Achieve the lowest possible pressure between the floor of the car and the track to increase adherence and therefore cornering speed

How achieved this goal the mechanics and engineers Lotus? Very briefly, based their innovations in aircraft wings. For them, the air flow generated by various forces on the wing, as well as various pressure changes, which results in a vertical force. To this end, based on three laws and principles:

  • Bernoulli principle In fluid dynamics, Bernoulli said inviscid a solid whose density is unchanged. the pressure decreases when the speed is higher circulating. Increased pressure to lower speed: the opposite effect also occurs. This is summarized in the famous Bernoulli equation.

 ground effect

  • Newton’s third law. or principle of action-reaction. States that any force exerted on a body corresponds another equal and opposite. Thus, when we hit a wall (we exert a force on it), the wall exerts a similar force and opposite on our hand (why it hurts and does not fall apart easily).

  • Coanda effect. Any fluid flowing around a solid tends to keep a path parallel to the surface. In other words, the streamlines of a fluid tend to approach the curved surface of the solid rather than remain constant

From these three laws, explain the operation. the wing of an airplane is relatively simple:

Imagine drafts as a set of parallel and malleable sheets. When air begins to approach the aircraft wing, this set of sheets is divided into two distinguishable masses, one that goes by the extrados (upper wing) and one who stands firm to the soffit (lower part of the wing). The extrados amounting to travel a higher trajectory with greater speed ; which continue through the soffit, they tour a lower trajectory with less speed. These speed variations affect the pressure.

 ground effect

As we can see in the picture, the “sheets” air running through the wing to the upper area is adapted to the wing contour – effect associated with fluid viscosity and the Coanda effect. This curvature is generated by a centripetal force (perpendicular to the tangent of the curve at any point), caused in turn by a pressure difference between the top sheet to the face and the underside of this sheet. Therefore, under closer we are to the top of the wing of the plane, the lower the pressure.

If we compare the pressure of the air layer closest to the extrados ( known as boundary layer) with the sheet closer to the soffit air, we see how the upper zone pressure is lower than the lower zone. This pressure difference generates a vertical force known as lift, which pushes the plane up and to achieve the balance of forces which tend all inertial systems.

ground effect

As a result, particles from the upper zone are redirected down (with a diagonal path) and apply a force to the rest of lower air particles when they leave the contour of the wing ( downwash ). A force equal and opposite Applying Newton’s third law, then arises, which also contributes to the lift of the aircraft.

Here also influence other parameters such as the angle of attack, thickness of the solid, the radii of curvature thereof, etc. These are modified in order to improve the efficiency of the wing, add new strength in different parts of the wing and achieve eg upside down flight aircraft.; but they are negligible for a basic explanation like this.

How soil of a racing car applies all this into effect? ​​

Now that we know the behavior of the airflow around the wing of a plane-and how these enable the aircraft to stay in the air, knowing the ground effect is really simple. Simply Let’s turn to the wing of the plane et voila! . And it is that by investing the plane’s wing forces are completely opposite, generating negative forces (down).

To understand it better, look at the following image of the Lotus 78, one of the first Formula 1 applying ground effect:

 ground effect

In this picture we see as the air divided again into two, but the extrados and the intrados are reversed. In this way, particles with higher speed and lower pressure to the area are located on the floor of the car, generating a pressure difference with respect top of the car causing a downward force in response.

Likewise, also identify outgoing diagonal drafts , which, by Newton’s third law, generate an extra force that “pushes” the car to the track, thus giving a better grip and therefore a higher cornering speed.

 ground effect

Lotus 78, one of the cars that best managed the ground effect.

The ground effect is partially limited in the major motorsport In the case of Formula 1, the ground effect was limited at the beginning of the decade of the eighty. The reason was none other than the insecurity of it. The cars began to fall excessively in this effect, with the result that the slightest variation in the circulating air flows underneath the car (which could be generated by a bump or a high piano) is translate into a serious accident . In fact, this life of the famous pilot Gilles Villeneuve ended.

Currently, the ground effect continues advantage in racing cars. The difference is that the bottom of it is flat, known as plano background, thus limiting the dependency on it and protecting the pilots in case of driving on an elevation. The magic of engineers, in this case, is to reduce the flow of air circulating under the car without touching the flat bottom (either with the front wings or small “lips” located around pontoons). Thus, the “empty” as possible.


Hypertext

What is the ground effect?
Source: english  
November 8, 2015


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