Wind anemometers in aerospace applications
The "airspeed tube" on an airplane is a typical Pitot tube wind speed sensor and is an extremely important measurement tool on an airplane. It must be installed in the area outside the airplane where the airflow is less affected by the airplane, usually directly in front of the nose, tail or wingtip. When the airplane flies forward, the airflow rushes into the airspeed tube, and the sensor at the end of the tube will feel the impact force of the airflow, i.e. the dynamic pressure. The faster the airplane flies, the greater the dynamic pressure. If you compare the pressure of the air at rest, i.e., the static pressure, with the dynamic pressure, you can see how fast the air is rushing in, i.e., how fast the airplane is flying. The tool used to compare the two pressures is a hollow circular box with a corrugated surface, called a membrane box, made of two very thin pieces of metal at the top and bottom. This box is sealed, but has a tube connected to the airspeed tube. If the airplane is going fast, the dynamic pressure increases, the pressure inside the membrane box increases, and the box bulges. The deformation of the diaphragm box can be measured by a device consisting of a small lever and a gear and displayed by a pointer, which is the simplest aircraft airspeed gauge.
The static pressure measured by the tube can also be used as a calculation parameter for the altimeter. If the membrane box is completely sealed, the pressure inside is always kept equal to the pressure of ground air. So that when the airplane flies into the air, the height increases, the static pressure measured by the air speed tube decreases, the membrane box will bulge, measuring the deformation of the membrane box can be measured by the height of the aircraft. This type of altimeter is called air pressure altimeter.
The speed measured by the airspeed tube is not the real speed of the airplane relative to the ground, but only the speed relative to the atmosphere, so it is called airspeed. If there is wind, the speed of the airplane relative to the ground (called ground speed) should be added to the wind speed (downwind flight) or subtracted from the wind speed (upwind flight).
With the development of modern science and technology, such as lasers and other new wind speed sensors have also begun to be used in wind speed detection. It is believed that in the near future, a variety of new wind speed sensors will be more and more used in construction machinery, railroads, ports, terminals, power plants, meteorology, ropeways, environment, greenhouses, breeding and other fields.
