Dayu Electronics Ultrasonic Doppler Flowmeter Culvert Detection

         Ultrasonic Doppler flowmeter is commonly used for water level, velocity, and flow monitoring in urban rivers, main canals of agricultural irrigation districts, urban sewage pipe networks, and urban stormwater pipe networks. Below, we will analyze a special case: culvert discharge flow monitoring.

          Environmental description: The culvert outlet is a circular pipe with a diameter of 600 mm, and the water pool depth is approximately 6.35 m. Wastewater flows out of the culvert at a slow velocity; the pool at the culvert outlet is about 1 meter wide and quite deep, with a water level of approximately 3.6 m during measurement.

　　In the culvert flow measurement (Figure 1), is the installation position of the ultrasonic Doppler velocity meter correct? In the above figure, the installation position is more than 1 meter outside the culvert outlet, with the probe close to the side wall. This installation method results in almost no velocity being measured because the water flows directly into the deeper treatment pool after exiting the culvert, making it nearly impossible to measure the velocity; the velocity meter requires a flow velocity above 0.02 m/s for detection. The water level measurement is not a problem, and the user reported that except for the lack of velocity, all other data are normal.

           From the data readings: the water level remained at 3.59 meters with millimeter-level accuracy; the temperature remained around 22.6 with an accuracy of 0.1°C; due to the improper installation position, the velocity data read 0, with a resolution of 0.001 m/s; the ultrasonic transmitted signal strength was readable, and all data were valid signals. Based on the above data analysis, the water level data essentially match the site conditions, and the velocity data also align with the installation position analysis.

      From the data readings: the water level remained at 3.59 meters with millimeter-level accuracy; the temperature remained around 22.6 with an accuracy of 0.1°C; due to the improper installation position, the velocity data read 0, with a resolution of 0.001 m/s; the ultrasonic transmitted signal strength was readable, and all data were valid signals. Based on the above data analysis, the water level data essentially match the site conditions, and the velocity data also align with the installation position analysis.

　　After communicating with the installation technicians, we provide the following recommendations:

　　1. Move the velocity meter installation point forward to the right, shifting it to the pipe outlet to accurately and reliably measure the flow velocity inside the pipe. (If possible, it is recommended to insert the velocity meter 0.5-1 meter into the pipe.)

　　Move the velocity meter closer to the pipe center, installing it at the center of the pipe outlet.