Pitot tube wind speed sensor working principle
Pitot tube, also known as "pitot tube", "wind speed tube", is a tubular device that measures the total pressure and static pressure of the airflow to determine the airflow velocity. It was named after the invention of H. Pitot in France.
It is difficult to directly measure the velocity of the airflow experimentally, but the pressure of the airflow can be easily measured with a manometer. It is mainly used to measure the speed of the aircraft, but also has many other functions. Therefore, the pitot tube can be used to measure the pressure, and then apply Bernoulli's theorem to calculate the velocity of the airflow. The pitot tube is composed of a double-layer casing with a round head (see figure). The diameter of the outer casing is D. A total pressure hole connected to the inner casing is opened at the center O of the round head to connect to one end of the pressure gauge. The diameter of the hole is 0.3-0.6D. Open a row of static pressure holes perpendicular to the outer pipe wall evenly along the circumferential direction at C on the side surface of the outer casing at a distance of about 3-8D, connect the other end of the manometer, place the Pitot tube in the steady airflow of the speed to be measured, make the axis of the pipe consistent with the direction of the airflow, and the front edge of the pipe faces the incoming flow. When the airflow is close to point O, its flow velocity gradually decreases until it stagnates to zero at point O. So what is measured at point O is the total pressure P. Secondly, because the pipe is very thin, point C is far enough away from point O, so the velocity and pressure at point C have basically recovered to the same value as the incoming flow velocity V and pressure P, so the static pressure measured at point C is. For low-speed flow (fluid can be considered approximately incompressible), the formula for determining the flow rate by Bernoulli's theorem is:
According to the total pressure and static pressure difference P-P measured by the manometer, and the density ρ of the fluid, the velocity of the airflow can be calculated according to formula (1).
