How can you estimate the aerodynamic level of a car based on its shape?

Air resistance is the largest and most important force encountered by a car while driving. The air resistance coefficient, also known as the drag coefficient, is an important factor in calculating the air resistance of a car. The drag coefficient can be measured in a wind tunnel.

When the vehicle is tested in the wind tunnel, the wind speed is used to simulate the speed of the car when driving, and then the test instrument is used to measure how much strength the car needs to resist the wind speed, so that the car will not be blown backwards by the wind. After measuring the required force, and then deducting the friction between the wheel and the ground, the rest is the wind resistance, and then the so-called drag coefficient can be calculated using the aerodynamic formula. Let's start with a brief introduction to two-wheel drive:

In the two-wheel drive form, it can be subdivided into front-rear-wheel drive (FR), front-wheel drive (FF), rear-wheel drive (RR), and mid-rear-wheel drive (MR) according to the position of the engine in the vehicle and the position of the drive wheels. At present, two-wheel drive off-road vehicles and sedans are most commonly used in the form of front-wheel drive and rear-wheel drive. <>

Sports cars really have to blow wind tunnels, and they are low-speed smoke wind tunnels. If you want to look at it, it is roughly to look at the size of the differential pressure resistance of the car, which can be interpreted irresponsibly as the maximum cross-sectional area should be as small as possible. Because the main resistance** in this environment of the car is the differential pressure resistance.

Modern cars have smooth surfaces and low speeds, so you don't need to think about viscous resistance. Usually at speed, there is no need to consider shock resistance. Not only racing, but also Volkswagen is also going to blow the air droplets, the disc is low, and the tire protrusion is small.

Dassault, the French aviation giant, said that a good fighter looks good. However, the visual optimization is not necessarily the aerodynamic optimization, and the modern automobile industry deliberately designs it to look good and attract customers for the sake of marketing; As for the aerodynamic level, the drag coefficient of modern ship-bottom cars is not much different, or even different, coupled with the influence of various factors in industrial design, manufacturers with high aerodynamic levels may not pursue the best aerodynamics. The drag coefficient of the car with a square head and square brain will be on the high side.

However, this does not mean that the more streamlined the car, the smaller the drag coefficient. For example, Volkswagen Beetle, the drag coefficient cd = what level is this, look at the general difference between the models, qualitatively look at them, the straight-back car (such as buses, buses, trucks, some SUVs) has the largest drag coefficient. The second is a step-back car (that is, a general three-box car, the more typical Jetta and Santana).

The one with the smallest drag coefficient is the fastback (commonly known as the hatchback, such as the Porsche 911). The drag coefficient of the three types of cars is very close and the aerodynamic performance is at the same level. It's really hard to judge just by the naked eye.

In fact, it is not easy for even a practitioner of automotive aerodynamics to accurately estimate the drag coefficient with CFD software. Therefore, the aerodynamic performance of the car and the drag coefficient need to be determined through wind tunnel tests. <>

What is the aerodynamics of the car, is it necessary to consider the average family car? The aerodynamics of the car is mainly the impact of the wind resistance coefficient on the driving at high speed, generally speaking, how large the ordinary car is streamlined, so as to reduce the wind resistance to a certain extent, reduce fuel consumption and improve the stability of the handling, and relatively speaking, the wind resistance of the off-road vehicle is greater than that of the car, and it is not as stable as the car in the handling.

Cars are paying more and more attention to aerodynamics, whether it's a supercar or a commercial car. Because the weight of the car will become lighter and lighter in the future, it is necessary to use air to "press" the car on the ground when driving at high speed, which is conducive to driving safety. Secondly, the level of air resistance is also closely related to the fuel consumption of the car.

Third, the reasonable use of air resistance can also dissipate heat from the engine and brake system. Therefore, at present, various manufacturers in the world attach great importance to the research of aerodynamics. Family cars also need to be considered, after all, it has something to do with fuel efficiency.

Of course, there is no need to think about it. Because the main function of an ordinary family car is transportation, there is no need to consider such complex factors.

This question is very profound, and it should be related to the height of the car and the angle of the corner, as for the formula, I really don't know.

The more streamlined the appearance of the car, the smaller the wind resistance, many cars are teardrop-shaped is the reason, reduce the wind resistance, and the chassis should be reduced, why the sports car is shorter than the general sedan is this reason, the closer to the ground, the more the airflow can reduce the airflow from the body underground, reduce the pressure of the airflow to lift the body, so that the grip of the car is enhanced.

The shape of the car does have a big impact on air resistance. So now there is a term for automobiles called "streamlined".

The so-called streamlined type is shaped like the shape of a drop of water dripping in the air. Such a shape has minimal air resistance. But it is impossible for a car to be designed in the shape of a drop of water, because the tail is too long and pointed to be practical.

Therefore, the shape of the first half of the water droplet can only be roughly applied to the shape of the car. The results of the experiment you are talking about can be compared to you for example, a car in the shape of a bus is faster than a car in the shape of a small car, and the two cars have the same performance, who is faster?