The Research And Application Of Digital Image Measurment Technique For Surface Flow Field And River-regime In Physical Model

This paper was supported by the National Natural Science Foundation of China. "The research of theory and technique about Surface Flow Field and River Regime in Sediment-laden River (50479068) "There are a lot of ways to measure velocity, but few can measure muili-point in physical model. As a result, This paper have set up a measuring system which can measure velocity field, meanwhile, applied edge detection technique, contour extraction Technique and neural network Technique, to get the data of river-regime. Paper introduced the detail of principle and realization ways about the system. Broadcasting seeding which can follow stream current and useing CCD cameras to record images of flow field, sending the images to computer, then classifying to PIV or PTV treatment by density of seedings in images. In PTV treatment, paper has founded image-reducing law, weighted law and circle fitting law for getting point of particle image, then applied hydrodynamic rule, we can get velocity of flow. In PIV treatment, paper has founded cross-correlation and surface fitting law, applying Hartly transformation in cross-correlation to get prime correlation coefficient, then doing surface fitting of correlation coefficient, we can get the most correlation coefficient derivation, this law can improve precision to subpixel. In river-regime treatment, it is first to compare effect of all edge-operator and choose edge operator with the best effect, then applied three-layer perceptron neural network in contour extracting to get data of river-regime.The software of system was compiled by visual C++6.0, including the capture, processing and save module. Paper has applied the system into physical model, and analyzed the result and error.