A Method and Instrument for Measurement of Sheet Flow Velocity Based on the Heat Transport Processes

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    Based on the heat transfer process in thin water streams, a tracer method was proposed to measure the flow velocity of water streams and a corresponding measurement system was designed. Different test conditions (5°, 10° and 20° slope, 2, 5 and 8 L/min flow rate) were designed on an indoor test slope to investigate the feasibility of the heat tracer measurement of thin water flow velocity and its influencing factors, using the salt tracer method as a control. The results showed that the proposed system measured the transport processes of the thermal tracer accurately and the flow velocities calculated basing on the thermal transport processes had a significant linear relationship with that by the salt tracer. The measured velocities ranged from 0.408 to 1.522 m/s with high accuracy, and the flow velocity by thermal tracer was 1.006 times of the salt tracer with the R2 of 0.993, which indicted the high reliability of the thermal tracing method. As affected by the tracer physical properties, the release mode had a significant effect on the measurement of sheet flow velocities under some hydraulic conditions, and it indicted that the velocities measured by salt and thermal tracer represented velocity of distinct layers of the flow. By using the combined salt-thermal tracer, the average of velocities by thermal and salt tracer can be taken as the velocity of the sheet flow, to improve the representativeness of the measurements under certain hydraulic conditions. The results of the study provided an alternative method for the accurate measurement of sheet flow velocities on slopes with complex underlying surface and high salt content, or under conditions of chemical free. Accurate measurement of thin flow velocities is of great importance for understanding in the field of surface hydrology and soil erosion.

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  • Received:May 26,2023
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  • Online: December 27,2023
  • Published: December 28,2023