| During the course of soil erosion on the slope occurred, the development processincludes erosion between rill, rill erosion and ephemeral gully erosion. In those processesthe velocity of slope runoff flow is an important parameter to evaluate soil erosion, andit's also a key factorin the soil erosion forecast. At present the majority of domestic andforeign research facilities still adopt the dye tracer method to survey velocity of sloperunoff flow. The method needs manual operation and has error produced by dye pervasion.Therefore, carrying out the velocity of slope runoff flow measurements real-time, on-lineand dynamic have vital scientific and practical value.Taking the velocity of slope runoff flow measurement methods as research content,the whole methods and its disadvantage are analyzed at present. The research of velocityof slope runoff flow is in majority indoor simulation the slope runoff flow. The runoffflow velocity measurement system using photoelectric sensor and tracing method isdeveloped to measure indoor simulation slope runoff flow. Primary attentions are paid tothe research of runoff flow velocity measurement system based on correlation and virtualinstrument. Those two systems have test on indoor simulation test-bed. The mainconclusion includes:1) The runoff flow velocity measurement system using photoelectric sensor and tracingmethod is developed. This system use foam particle as a tracer to conquer thedisadvantages of dye pervasion and the error of human vision. Photoelectric sensorand virtual instrument technology is used to enhance the precision of time record. Theexperiment completed and the result indicate that using photoelectric sensor andtracing method is feasible, the test-bed can recycle water and soil and the velocityvariable rang satisfies needs. The normalization estimator K is found, in certain scopesthis estimator can consider to be invariable and have no relations with sedimentconcentration.2) The system using photoelectric sensor and tracing method measures runoff flowvelocity accurately at the scope of 0～400 kg/m3 sediment concentration and 0～25°of slope gradient. It is foundthat the greatest relative error of the system is2.29%. This measurement system provides a new, valid method for speedy andaccurate measurement of runoff flow velocity. 3) Developed a runoff flow velocity measurement system based on correlation flowvelocity measurement theory and virtual instrument technology. This system iscomposed of photoelectric sensor, data acquiring mode and measuring and controllingsoftware.4) The photoelectric sensor have developed and used to survey runoff flow random noisesignal. The LED and phototransistor is chosen for photoelectric sensor whoseprocessing circuit is designed. This sensor can acquire noise signal at the scope of 6～13mm.5) FFT fast correlation algorithm is used and the operation time of N point can bereduced from (N2+N (N-1)) to (N+1.5 log2 N). System speed of response enhancesgreatly.6) The system based on correlation and virtual instrument measures runoff flow velocityaccurately at the scope of 0～400 kg/m3 sediment concentration and 0～25°of slopegradient. The greatest error of this system is 4.8%. Error after standardize of thesystem is 2.29%, so the accuracy is high. The precision of this system have no relationwith sediment concentration and slope gradient. Therefore, this system has goodcompatibility.7) The experiment results indicate that runoff flow velocity measurement system basedon correlation and virtual instrument can fast, real-time, on-line survey the sloperunoff flow velocity. |
