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ADCP (Acoustic Doppler Velocity Profiler) flow measurement is currently one of the most advanced river velocity and flow measurement equipment in the world. It uses the Doppler effect principle to measure flow velocity and helps hydrological departments to obtain river flow velocity and flow information online and in real time. By using ADCP, the departmemt can grasp the operation status and changing laws of rivers, provide reliable data for flood prevention and flood control decision-making, so as to minimize or avoid casualties and property losses caused by flood disasters, and ensure the safety of people’s lives and property.
The Luokou Hydrological Station, located on the south bank of the Yellow River Embankment in Luokou Town, Jinan City, Shandong Province, has been monitoring and reporting water regimes for the National Defense General and the Yellow River General Defense all the year round, providing accurate hydrological data information for flood control and drought relief, water scheduling, engineering construction, and local economic development in the lower reaches of the Yellow River in Shandong. Due to the coming of the flood season, affected by the water and sediment regulation and scouring of the upper reaches of the Yellow River, the river water in the eastern section of the Yellow River has a large sediment concentration, and the flow rate and discharge increase, making the Luokou Hydrological Station always facing the problem of flow measurement in an environment with a large sediment concentration.
In the environment with large sediment concentration, the current meter and ADCP used in the Luokou hydrological station cannot be tested normally. The flow meter test takes a long time, which takes about 1 hour, and the test method is relatively complicated, and has high requirements for the test section. And the current meter is labor-intensive, requiring operators to drive the test boat for testing, and there are certain hidden dangers to personal safety. However, when ADCP faces a large sediment concentration, the transmitted acoustic signal will be quickly absorbed, and effective echoes cannot be obtained, resulting in the inability to measure bottom tracking information, making it difficult to obtain flow rate and flow data.
Due to the harsh conditions of the high sediment concentration in the Yellow River, ADCP has no bottom tracking information and cannot be tested separately. Therefore, Hi-Target provided the solution of iFlow RP600 ADCP equipped with HD-MAX DF dual-frequency echo sounder and K20 high-precision split RTK.
In the scheme, the HD-MAX DF dual-frequency echo sounder is used to measure the water depth information to supplement the water depth parameters in the ADCP bottom tracking information, and the K20 high-precision split RTK is used to measure the speed to supplement the relative ground velocity of the equipment in the ADCP bottom tracking information. The measurement data of each device is output to the iFlow flow measurement software in real time through the matching software of both HD-MAX DF dual-frequency echo sounder and K20 high-precision split RTK, and integrated with the relative flow velocity information measured by iFlow RP600 ADCP, so as to calculate the flow and complete this ADCP flow measurement operation task.
1. Equipment installation
In order to reduce the measurement error caused by the distance between each device during the joint measurement, the iFlow RP600 ADCP is installed on the right front of the steel survey vessel in a sideways installation, the HD-MAX DF dual-frequency echo sounder is installed in front of the iFlow RP600 ADCP for narrowing the distance between the HD-MAX DF dual-frequency echo sounder and the iFlow RP600 ADCP, and the two positioning directional antennas of the K20 high-precision split RTK are installed directly above the fixed bracket of the iFlow RP600 ADCP. Meanwhile, to improve the accuracy and quality of the joint measurement, Hi-Target testers made a deviation correction of -4°between the antenna baseline of the K20 high-precision split RTK and the iFlow RP600 ADCP heading installation angle.
2. Data collection
In this flow measurement, the iFlow RP600 ADCP performed 2 measurement rounds (a total of 4 half measurement rounds). The start time and recorded data files of each test are shown in the table on the right.
3. Data analysis
Based on the iFlow flow measurement software, various information such as the overall flow velocity profile of the test section of the Luokou section can be obtained.
Based on the iFlow flow measurement software, it is possible to obtain the flow, velocity, area, river width and other parameter values obtained from the current measurement of the cross-section and the statistical analysis and calculation of the data.
Based on the iFlow flow measurement software, it is possible to obtain a schematic diagram of the curve of the measured flow of the entire section as a function of the measurement time, thereby clearly obtaining the trend of the flow change with time.
Based on the iFlow flow measurement software, the flow velocity and echo intensity measured by the iFlow RP600 ADCP corresponding to the 4 beams at each measurement time can be obtained.
Based on the iFlow flow measurement software, the GNSS information corresponding to each burst time can be obtained.
Based on the iFlow flow measurement software, the current track trajectory line of the steel measurement vessel and the corresponding flow velocity vector can be obtained.
Based on the iFlow flow measurement software, the flow result table can be automatically generated, and the configuration information of the current measurement, flow parameter measurement results and measurement average results can be automatically recorded.
The maximum relative deviation of the 4 half measurement rounds of the iFlow RP600 ADCP is 2.12%, and the self-deviation (standard deviation) of the cross-section average flow velocity, flow direction, river width and cross-sectional area parameters are all between 0.6% and 2.7%, meeting the measurement specifications accuracy requirements, and achieve high test accuracy. Among them, the relative deviation between the average flow rate measured by the iFlow RP600 ADCP and the flow rate at the Luokou Hydrological Station released by the official forecast of the day is 1.01%. It can be concluded that the data measured by iFlow RP600 ADCP under the condition of relatively large sediment concentration has high precision and accuracy, and this joint test has been a complete success.
The joint test conducted by Luokou hydrological station and Hi-Target shows that the joint use of Hi-Target iFlow RP600 ADCP, HD-MAX DF dual frequency sounder and K20 high precision split RTK can overcome the influence of the harsh conditions of large sand content and complete the measurement task of ADCP, which provides more means and methods to measure the flow in the environment of the Yellow River with large sand content.
The quiz also demonstrated the excellent performance of the iFlow RP600 ADCP in terms of peripheral expansion, installation and commissioning, support software, and flow measurement results.
In terms of peripheral expansion, iFlow RP600 ADCP can be used for ADCP flow calculation by inputting other peripheral parameters reasonably according to demand, and the device has good peripheral compatibility.
For installation and commissioning, the installation and commissioning process of iFlow RP600 type ADCP is convenient and quick, and the connection with HD-MAX DF dual frequency echo sounder and K20 high precision split RTK is reliable and can be used in environments with large sand concentrations.
For the supporting software, the iFlow flow measurement software can present a wealth of measurement information during the testing process and the data analysis process after the measurement is completed, and has a good user experience.
For the flow measurement results, the self-deviation (standard deviation) of the data such as flow, flow velocity, bottom velocity, and cross-sectional area measured by the iFlow RP600 ADCP is within 2.7%, and the measurement accuracy meets the requirements of the ADCP flow inspection specification.
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