The application research of aerodynamics in racing design has only emerged in recent 20 years. In the 1960s, F 1 team realized that installing spoiler components such as wing plates in different parts of the car body could effectively improve the speed of the car in corners. However, due to the lack of theoretical guidance at that time, the team did not have a forming concept about where these wings should be installed, how big the wing area should be and how the angle should be. Everyone is constantly exploring and trying. In addition, the processing technology was not mature at that time, and there were many examples of casualties caused by wing plate falling off during the competition. Therefore, it was once forbidden to install aerodynamic components on racing cars. However, with the development of aerodynamic theory system and the rise of computer technology, it is possible for the team to deeply study the influence of aerodynamics on racing.
Several kinds of resistance affecting the speed of racing car
Aerodynamics seems to be a very nerve-racking name: can air also generate electricity? The aerodynamic force mentioned here is actually not to turn air into the driving force of the racing car, but to turn the air pressure generated by the high-speed air flow when the racing car is driving at high speed into a force beneficial to the racing car. First of all, let's analyze what forces constitute the resistance to the car during the movement of the car.
First of all, all liquids and gases are made up of slidable particles. When a liquid or gas passes through a surface, the particle layer closest to the surface will adhere to the surface. Because the particle layer on the surface of the object is relatively static, the movement speed of particles above this layer slows down. Similarly, the movement of particles above this layer will also be affected, resulting in a slower sliding speed, but the reduction is reduced. The farther away from the surface of the object, the less the particle layer is affected until they move as free particles. The layer that slows down the particle sliding speed is called the critical layer. It appears on the surface of the object, forming surface friction. Readers who have studied physics in middle school and have a preliminary understanding of molecular mechanics should understand this easily.
Force needs to change the direction of molecular motion, so a second force is formed, called shape stress. In aerodynamics, size is also a factor. The smaller the front nose of a car (when you see the front part of the car), the smaller the area where molecules change direction, and the easier it is to pass. A small part of the engine's power is absorbed by the flowing air, and most of it is converted into the power to fly on the track. With the designated engine, the car can run faster.
However, things are not that simple-the shape of an object is also very important, which determines the difficulty of molecular movement. Air is used to adhering to the surface of objects, so it is much more difficult to pull a plate with a smooth surface in the airflow than to pull an arc bowl similar to the front nose. The airflow will turn over on the bowl surface, but it will stick to the glossy surface of the plate. Aerodynamic research shows that teardrop-shaped objects are the easiest to pass through airflow. Most people may find it strange that the round head is in front and the tip is in the back.
When the airflow moves along a curve (or changes direction), as long as it is thin, its motion will not change. But when the curve has a certain shape, or the direction changes suddenly (just like meeting a sharp object), the airflow will split in two on the surface of the object, and there is not enough energy to pass through the surface. This situation needs to be avoided, because the critical layer is very thick, and the airflow in front will slow down, blocking the airflow behind like a solid surface. Therefore, sharp objects can only produce greater resistance through airflow.
So is a round object ideal in air movement? No! When a ball is in air movement, the airflow will initially change with the arc of the ball. But when it passes through the maximum radius of the ball, the airflow will still chase the arc of the ball, but at this time the spherical surface has been sharply reduced. This is the most difficult movement of airflow, so when the airflow passes through the radius point, it no longer adheres to the surface of the sphere and becomes messy. The dispersed airflow will rotate in disorder, resulting in less pressure than the freely moving airflow, so it will produce gravity to hinder the movement of the sphere and slow down its movement speed. As for the teardrop-shaped object mentioned above, when the airflow passes through an arc similar to a sphere and reaches the critical failure point, the teardrop-shaped object will have an inclined surface to support the movement of the airflow. Objects can pass through the airflow cleanly with minimal resistance. For a simple example, a free-falling suspended droplet must be teardrop-shaped, because such air resistance is the smallest, and if it is just a simple sphere, it will only cause greater resistance.
The last kind of stress is induced stress, which is the inevitable product of downward pressure in the form of air vortex, which can be clearly seen in the water vapor flowing through the tail of racing car in rainy days.
Design inspiration of key pneumatic components such as wing plate: obtaining downforce from flowing air.
Many people will ask: since there is shape stress, why is the shape of F 1 car not made into a complete teardrop shape? Isn't this the least resistance? Yes, but not all right. The designer of F 1 racing car body should first consider the problem of getting enough downforce to make the tire have enough grip, and then the resistance. This is because: first, racing cars often need to accelerate and decelerate quickly, and at this time, sufficient ground grip must be ensured; Second, when the car changes direction during driving, it is easily affected by centrifugal force. At this time, it is difficult to maintain the grip of automobile tires on the ground only by the weight of the car body, and it is easy to get out of control. The higher the grip, the faster the car will turn the corner. Thirdly, the engine of F 1 racing car can output enough horsepower, so that the racing car can still achieve high speed under considerable resistance. Under the joint action of these three factors, grasping power has become the first element. So, how to get the downforce from the flowing air?
The answer is actually very simple, just look at the wings of the plane. In aerodynamics, the role of wings is to generate lift when air flows. The principle is this: when the air flows through the wing, some of it flows above the wing plate, some of it flows below, and finally these two parts of air reunite behind the wing plate. The wing design of an aircraft makes the upper surface of the wing longer than the lower surface, so that the air speed above the wing is faster than that below the wing. A wise man named Bernoulli found that the faster the air speed, the less its density and the less its air pressure. In this way, the air pressure above the wing of the aircraft is smaller than that below, thus generating lift.
What about racing? -As long as we turn the shape of the wing upside down, we can generate downward pressure, as shown in the figure (note the cross-sectional shape of key pneumatic components such as wing plate-teardrop shape).
This seems to be a simple principle, but it was not until the late 1970s that anyone thought of it. This person is the current chief designer of McLaren-adrian newey. This is the topic of his graduation thesis when he graduated from Southampton University. At that time, he was still a fledgling teenager, but this groundbreaking idea made him the originator of the combination of F 1 racing design and aerodynamics.
When the car is so close to the ground, similar principles can be brought into full play as it gets closer to the ground. In the early 1980s, Lotus racing car had this kind of chassis, which was then called "ground effect" chassis and achieved remarkable results. Later, due to the prohibition of the competition, it did not develop further.
Exploration of racing car body designers
Body designers must clearly analyze various factors that affect aerodynamic performance. Fortunately, according to years of experience, the aerodynamic performance of racing cars is affected by the following factors: air density, air speed, cross-sectional area of stress surface and lift coefficient (or drag coefficient).
Among them, the biggest influence is speed, because force is directly proportional to the square of speed, that is to say, if the speed is tripled, the force will be increased to nine times! Air density is related to temperature, humidity and altitude, which is why the aerodynamic adjustment of the car should refer to the temperature, air humidity and altitude of the track at that time.
The lift coefficient reflects the ability of the stressed surface to generate lift (resistance), which is usually determined by the smoothness and shape of the material. A few seemingly simple numbers, but the meaning they represent is by no means simple. The search for perfect aerodynamic settings (maximum downforce and minimum drag) has never stopped. Sometimes even a master like Newey may not find the best solution that suits the car and the track situation at that time.