| The vibration of hydraulic structure caused by high speed discharge becomes a great problem which can not be neglect in engineering construction. For more and more hydraulic structure are being built with a light shape, which will work under high water head. The cavitations and vibrations of hydraulic structure and the scour of river bank have direct relationship with the fluctuating pressures caused by discharge flood. For the turbulent structure having not been revealed fully, the fluctuating pressures are hard to calculate in theory. Estimate of fluctuating pressures is mainly depending on the data from model experiments recently. Similarity law of fluctuating pressures is the conversion rule between model and prototype, so it is quite important for estimating dynamic force.Hydraulic jump is a common kind of hydraulic phenomena. Turbulence appears when water flow transit from low water depth to high water depth, and there would be dynamic force on the slabs. In this paper, hydraulic jump was studied, model of hydraulic jump with different Fr number and different scale were designed, and the data of fluctuating pressures were analyzed, in order to find the similarity law of hydraulic jump. The main work of this paper can be concluded as follows:(1) Designing hydraulic jump model of different scale based on different Fr number, trying to find the relationship between the shape of hydraulic jump and Fr number. Prototype law of average pressure was found through comparison.(2) The coefficient K for estimating maximum positive fluctuations in different conditions was calculated, and the probability distribution of coefficient K was researched. By introducing dimensionless pressure coefficientβ, the similarity law of fluctuating pressures in extent-domain was achieved.(3) The probability distributions of fluctuating pressures were estimated using kurtosis coefficient C Eand skewness coefficientCs . The similarity law of fluctuating pressures in probability distribution was achieved. By using dimensional correlation function, the extent of eddies in different hydraulic jump were compared.(4) By using the Fourier transform, the spectrums of dynamic force under different condition were analyzed. The similarity law of fluctuating pressures in frequency-domain was achieved by comparing the peak spectrums and the whole spectrums. |
