| oil erosion is now regarded as a global environmental problem, which catches more and more attention worldwide. Serious soil erosion exacerbated the deterioration of ecological environment, which restricts the sustainable development of society and economy. Runoff plot, as a normal but important research method in of soil erosion, is applied all over the world, of which water and sediment measurement play an important role in quantitative analysis of soil erosion. Increasing the measurement accuracy of runoff and sediment in flow-dividing device of plot collection systems, and is the key to precisely obtain the soil erosion data.The simulated flow-dividing experiment was carried out to quality the effects of runoff discharge( 10, 20, 40, 60 L/min), collecting pipe length( 0.1, 0.2, 0.4, 0.6, 0.8m) and the inflow position( 0.2, 0.4, 0.6m) to the process of two flow-dividing devices, which error analysis and correction of flow-dividing device of runoff plot. The main experiments and conclusions are as following:1. When the lengths of flow-dividing pipes are the same, the measurement accuracy of flow-dividing device in cylindrical design was generally higher. The runoff-dividing coefficient and sediment-dividing coefficient of two flow-dividing devices were affected little. When discharge increased, the runoff-dividing coefficient in cubic device decreased slightly, indicating the change of the flow-dividing process of cubic device is greatly influenced by discharge. The coefficient of variation and suspended sediment decreased with an increase of discharge, significantly, in flow discharge range of 10~40 L/min. The runoff sediment concentration decreased with increasing the distance between flow-dividing hole and the drowning point, both showed a good linear relationship.2. The runoff-dividing and sediment-dividing coefficient increase as the length of main collection pipe increases, resulting in a reduction of runoff volume and sediment, by which caused large test error. The maximum error reached a peak value in the largest length of main collection pipe. Sediment concentration in different flow-dividing period process kept relatively stable later for all experiments. The remaining amount of sediment in main collection pipe was affected by both discharge and the pipe length, especially pipe length is greater than 0.4m.3. The relationship between the total head in single flow-dividing hole and discharge can be reflected by power function, and reached a significant level. The differences between theoretical calculations and experiment results decrease obviously, suggesting the influences from loss of resistance along the way decrease gradually. As the key factor, the ratio between flow-dividing pipe length and imported water depth was determined by runoff plot design and discharge.4. Combining experiment results, the cylindrical flow-dividing device is considered to be more reasonable, which obtaining higher measurement accuracy by reducing the effects of discharge on the influence coefficient. In addition, when the center of the cylindrical is the entrance of the runoff, the distances between the entrance and the flow-dividing holes were the same, so it could reduce the differences of sedimentation when flow was moving from the entrance to different flow-dividing holes. Secondly, extending the length of main collection pipe can cause great errors for water and sediment tests,which should be obtained adequate attention. The lengths of all the collecting pipes were the same, which led to a consistency of the hydraulic parameters of the flow-dividing process such as flow pattern and resistance head. Under the principle of no overflow happening, increasing the number of flow-dividing holes or reducing the inside diameter and the length of flow-dividing pipe, could produce high accurate measurement of runoff volume and sediment concentration by increasing the probability of full pipe flow and, then reducing the impact of fluid drag and head loss. |
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