How to measure flow in an open channel?
Open channel flow meters can be used in relatively harsh environments. They can measure flow in urban water supply diversion channels, sewage treatment inflow and outflow channels, and industrial wastewater discharge.
Now, here are specific methods for open channel flow measurement.
Open channel flow meters use two measurement methods: the water level method and the velocity-area method.
The water level method measures the water level upstream (or both upstream and downstream) of a water-metering structure and converts it into flow using empirical formulas or experimental curves. Water level flow meters require a water-metering structure and are not very accurate.
The velocity-area method is a simple flow measurement method in open channels. It calculates the flow rate by measuring the cross-sectional area of the water flow and the cross-sectional flow velocity. The velocity-area method offers high accuracy and is unaffected by downstream headwater. Radar flow meters, electromagnetic flow meters, or Doppler flow meters can be used.
What is ultrasonic open channel flow measurement?
The core design of an ultrasonic open channel flow meter is based on the physical properties of sound waves. It uses the propagation features of ultrasonic pulses in flowing water to measure water velocity and water level. Typically installed above or alongside an open channel, the device contains one or more sensor probes that transmit and receive ultrasonic signals.
When an ultrasonic pulse is emitted from a probe, it travels through the air or water medium, interacts with the water flow, and then returns to the probe. By calculating the difference in ultrasonic pulse propagation time, the ultrasonic flow meter can infer water velocity. Combined with the data from the water level meter, a PLC system or computer can accurately calculate the flow rate.
