Study On The Similarity Law And Characteristics Of Fluctuating Pressures In Supercritical Flow

At present, high-speed flow pressure pulsation effects of hydraulic structures isan issue of common concern engineering, theoretical study of fluctuating pressurecomes across bottleneck, resulting in a lack of theoretical model calculations,prototype observation is limited by space. People pay more attention to the use ofhydraulic model test flow fluctuating pressure, the problem of similarity law offluctuating pressures in supercritical flow is unsolved. The results obtained in themodel cannot be completely applied to the actual project, namely the amplitude ofpressure pulsation can be converted to the prototype use gravity similarity criterion,but the frequency cannot be converted to the prototype,the stable structure analysisbrings disorder, bring problem to structural stability analysis.In this paper, three chute models were used to analyze the similarity law andcharacteristics of fluctuating pressures in supercritical flow. Slove the problem ofsimilarity law of fluctuating pressures in supercritical flow. Analyze the differentbetween supercritical flow in the chute and the flow in the hydraulic jump regionusing two hydraulic models. The main work of this paper can be concluded asfollows:(1) Study on a chute model, carried out series of scale ratio test, the coefficient Kfor estimating maximum positive fluctuations in different conditions was calculated,and the probability distribution of coefficient K was researched. By calculatingdimensionless pressure coefficient β, the similarity law of fluctuating pressures inextent-domain was achieved. The probability distributions of fluctuating pressureswere estimated using kurtosis coefficient CEand skewness coefficient Cs. Thesimilarity law of fluctuating pressures in probability distribution was achieved. Byusing dimensional correlation function, the extent of eddies in different hydraulicjump were compared. By using the Fourier transform, the spectrums of dynamic forceunder different condition were analyzed.(2) Study on two actual spillway projects, carry out series of scale ratio test. Usethe same analysis method with the chute model. The spectrums of dynamic forceunder different condition were analyzed.(3)Study on the chute section and the stilling basin section of a spillway project.This paper analyzed the different between supercritical flow in the chute and the flowin the hydraulic jump region. The study includes dimensionless pressure coefficient β, coefficient K, kurtosis coefficient CEand skewness coefficient Cs, frequencycharacteristic values and correlation.