On the effects of a negative step in pressure fluctuations at the bottom of a hydraulic jump

Experimental evidence of the statistical structures of turbulence pressure fluctuations at the bottom of hydraulic jumps over a negative step is brought out in this paper. Special attention is paid to the definition of the extreme Values and of the spatial correlation structures of the anisotropic field of fluctuating pressures in view of their relevance in the structural design of the lining in spillway stilling basins. The analysis is performed in the case of B-jump and Wave-jump considering two different heights of the drop for Froude numbers ranging between 6 and 9.5. Moreover, the effect of the shape of the drop on the hydraulic jump has been investigated using the abrupt step as well as the rounded one. The experimental results herein reported may be helpful in the design of a stilling basin with a negative step, with particular reference to the thickness of the concrete slabs required to ensure the stability of the linings.