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Characteristic Depth and Pressure Profiles in Skimming Flow over Stepped Spillways

Author(s): Jorge Matos; Marti Sanchez; Antonio Quintela; Josep Dolz

Linked Author(s): Jorge Matos

Keywords: Characteristic depth; Equivalent clear water depth; Mean pressure; Wavypattern; Recirculating vortices

Abstract: Experimental investigations have been conducted in two steep stepped spillway model chutes assembled at National Laboratory of Civil Engineering (LNEC) -Lisbon and at the Technical University of Catalunya (UPC) –Barcelona, respectively. In LNEC’s facility, the research focussed essentially on air concentration and velocity data along the chute, whereas on UPC, main attention was given to pressure fluctuations on the vertical and horizontal step faces. Some flow visualisation techniques have also been used to analyse the recirculating vortices formed in the step cavities. The experimental results indicate that the characteristic depth profiles (namely, those of the characteristic depth where the local air concentration is 90% , Y90), as well as the mean pressure profiles (the pressure was measured on the centre of the horizontal face of the steps) exhibit a wavy pattern down the stepped chute. They also illustrate that the recirculating vortices are three-dimensional and that their turbulence intensity appears to be maximum near the pseudo-bottom formed by the external edges of the steps, due to the transmission of shear stress from the skimming flow.


Year: 1999

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