PHYSICAL MODELLING AND DESIGN ESTIMATION OF INSTANTANEOUS PRESSURES IN STILLING BASINS

摘要

This paper deals on the estimation of peak values of pressure fluctuations in stilling basins,rnby means of systematic experimental data from laboratory tests on free hydraulic jumprnover an horizontal floor. This "design curves" can be applied to a particular spillwayrnstructure, which don't have all the geometric characteristics concerning the laboratoryrndevice.rnFor this comparison the Yacyretá Dam main stilling basin, in the Paraná River, wasrnselected. The spillway has very large specific discharge and relative small chute. In orderrnto evaluate the degree of approximation predicted by the preliminary estimation based onrnpressure fluctuations on a two-dimensional free hydraulic jump on an horizontal floorrnrelated to the Yacyretá Dam stilling basin (which has spillway piers upstream, floor with arncertain slope and an end sill), some statistic parameters were selected.rnThe comparison was made for the r.m.s. amplitude of pressure fluctuations, the peakrnamplitudes for 0.1% and 99.9% of probability to be exceeded by more negative values andrnthe skewness of the probability density function of pressure amplitudes.rnAlthough the differences between the basic research data and the real structure values,rnthe proposed estimation provide useful information for the preliminary design of stillingrnbasins. The structure must be verified by means of a Froudian hydraulic model at arngenerous length scale.