There is always an antenna-like object at the rear of the roof, which looks like a shark fin exposed from the water, so this antenna is also called "shark fin antenna".
This design was invented by an Australian aircraft engineer, but it is not the first in a strict sense, because it is the same as the vertical tail of an aircraft, but it was first applied to cars from this person. However, the brand that really applies is BMW. Only after acquiring the patent did such an antenna come into being-the key point is that the acquisition cost is quite high. Why does BMW favor this design?
Learning point
The "shark's fin" design is not only used in cars, but also in airplanes. For example, Boeing aircraft has this design, and it is not the traditional vertical tail. The advantage of this design is that it can cut the air vortex at the top of the fuselage.
Aircraft in flight are affected by airflow from different angles, but the airflow formed by frontal collision with the wind can not form regular airflow at the top, and the turbulence formed after collision will affect stability; But through this raised small shark fin, the airflow can be cut off and turned again. Isn't it amazing?
The design of automobile shark fin is basically the same as that of aircraft, and the airflow on the roof is theoretically to form downward pressure; However, turbulence will affect the effect. For the rear gear with large inclination angle, the airflow may form turbulence in the rear gear due to gravity.
Then before this, cut off the shark fin antenna to form two regular airflow sections, which will better improve the pressure under the trunk; At the same time, the downward pressure of the rear wheel increases, and reducing the power loss on the wheel can effectively improve the fuel consumption performance. The wind tunnel test results show that this antenna can reduce the single-digit percentage of fuel consumption, and the degree of reduction will be different for different vehicles.
Note: SUV generally does not need to use this design, because the airflow at the tail will form turbulence after leaving the roof, which is the result of the body structure design; Therefore, adding shark fins only plays an aesthetic role, unless it is a special coupe crossover model.
As for some vehicles, it is meaningless to install shark fin antenna in the front of the roof, because the airflow in the front is regular, and shark fin can only play a counterproductive role; The key point is that there will be more "auto parts wind" in this installation, and the antenna is not used indiscriminately.
Other functions
1: Shark fin antenna exists purely as decoration, but at least it will be "grounded" in amateur design; That is, connect a wire to the antenna to guide the static electricity generated in the dry environment to the top cover and release it.
This is equivalent to a "sky-to-sky electrostatic discharger", which uses the characteristics of cutting-edge electrons to reduce the static electricity of steel plates; This can not only reduce the impact on the driving experience, but also protect the body electronic equipment-the instantaneous voltage of static electricity can be in the range of 1500~35000 volts, and the general household electricity is only 220 V.
The car radio station also relies on this antenna to receive signals. If there is no shark fin design, the best standard is to contact the body steel plate; Because the steel plate can form a grounding grid for the antenna, it is helpful for signal gain.
This is the best choice for radio antenna, which is fixed on the roof with suction cups. Compared with the fixed-side UV or short-wave antenna, the transmitting and receiving effect will be more ideal. It's good to know shark fin antenna. It is not recommended to install it on vehicles without this antenna, because different brands of vehicles will always have different considerations when designing according to aerodynamics, and some vehicles will only be counterproductive after installation.
This article comes from car home, the author of the car manufacturer, and does not represent car home's position.