Spillway Stilling Basins Lining Design via Taylor Hypothesis

Abstract

The paper presents the results from detailed experiments of the statistical structure of turbulence pressure fluctuations at the bottom of hydraulic jumps, with special reference to the spillway stilling basins lining design. Here, the whole spatial correlation structure of the fluctuating pressure field is required in order to evaluate slab stability. This is computed via simultaneous acquisition of the point pressure fluctuations on a dense grid in the hydraulic jump region, requiring a severe experimental work. As an alternative, one can evaluate the pressure spatial correlation structure via autocorrelation using one point pressure acquisition and applying the Taylor hypothesis. To adopt the Taylor hypothesis, one must know the pressure propagation celerity in space that can be obtained by comparing the whole spatial pressure correlation with the pivot point pressure autocorrelation. The experiments were performed by simultaneous pressure acquisitions at the bottom of a hydraulic jump for Froude numbers of the incident flow ranging from 4.9 to 10.3. From experiments, a criterion to define the pressure celerity as a function of the incident flow velocity is presented. The results highlight a good agreement between the relevant pressure statistical parameters as measured and the ones computed using the Taylor hypothesis. The comparison between the slab thicknesses, as computed via Taylor hypothesis, with the ones retrievable in literature, as obtained by direct force measurement on instrumented slabs in laboratory conditions, highlights the accuracy of the proposed approach that presents undeniable practical advantages.