Overview of the water velocity measurement system.
The purpose of observing water flow is to grasp its characteristics, study its temporal changes and spatial distribution, and find out its activity law through analysis and research. River flow velocity measurement is an important task in river management, which is helpful to ensure the stability of the river level, the safety of embankments, the prevention of flood disasters, the protection of people's lives and property, the maintenance of the water ecological environment, and the realization of sustainable use of water resources.
With its safe, flexible and convenient working mode, combined with the requirements of demand-oriented and innovative services, the UAV flow measurement system can reduce the risk coefficient of manual measurement, improve work efficiency and measurement accuracy under the conditions of faster emergency requirements for hydrological testing and harsh environment.
1) Unmanned aerial vehicle: used to mount radar velocity meter, wireless camera and other equipment. (2) Stabilizing the gimbal: The attitude of the radar velocity meter can be adjusted to meet the installation requirements of the radar velocity meter.
3) Radar velocity meter: use the Doppler effect to measure the flow velocity on the surface of the water body.
4) Radio communication system: used to transmit UAV control instructions and information of related mounted equipment.
5) Ground control system: used to send instructions and receive relevant data from UAVs and other devices.
6) Positioning system: Integrate centimeter-level Qianxun high-precision positioning service.
7) Power supply system: power supply to the whole system.
The radar velocity meter uses the Doppler effect principle to measure the surface velocity of the fluid. In the field of acoustics, when there is a relative motion between the sound source and the receiver (i.e., the probe and the reflector), the frequency of the echo will change, and this change in frequency is called the frequency shift, or Doppler effect. When the radar velocity meter and the water body move at a relative velocity v, the frequency of the electromagnetic waves received by the radar velocity meter is different from the frequency of the electromagnetic waves emitted by the radar itself, and this frequency difference is called the Doppler shift. By calculating the Doppler shift as a function of v, the surface velocity of the fluid is obtained.
The perpendicular line is laid in accordance with the requirements of GB 50179-2015 River Flow Test Specification. As shown in the figure, the red line is the perpendicular line set by the current measurement section, with a total of 10 perpendicular lines, and the section is divided into 11 small sections. The average perpendicular velocity vn vertical on each perpendicular line is the product of the surface velocity vn table and the water surface velocity coefficient k measured by the radar velocity meter at the radar velocity meter at the measurement point, that is, vn vertical = vn table*k, where n represents the corresponding perpendicular serial number. The flow rate of a small cross-section can be calculated according to the formula.
1) Plane microstrip radar non-contact detection, not affected by climate, sediment and floating objects.
2) Fast and accurate measurement, stable data output, and suitable for high flow velocity environment during flood period.
3) The antenna transmission frequency is flexible and adjustable, which can effectively avoid mutual interference of multiple products.
4) A variety of data communication interfaces can be set to facilitate the docking of user systems.
5) The combination of measurement operation and sleep mode can save energy and reduce consumption.
6) Anti-internal condensation, waterproof, lightning protection design, suitable for all kinds of field environments.