In this work, we investigate the temporal evolution of the jet-driven scour depth in a pothole lying on a cohesionless granular bed by using diverse approaches. First, we present new experiments which encompass cases with jet angles ranging from 45° to 90° from the horizontal, several initial water depths, and different particle sizes, supplementing experiments developed recently by the last two authors. In particular, we address relatively large angles, mostly absent in previous analyses. Our results initially confirm the existence of two very different stages in the scour process, essentially overlooked in datasets used to obtain the traditional formulas—developing and developed phases; they then provide unprecedented evidence of the very distinct behavior at 90°, characterized by a step-wise behavior. Second, after revisiting the rationale of a theory for the equilibrium condition developed elsewhere by the first author and a collaborator, we employ the existing and new datasets to determine the multiplicative constants embedded in the equilibrium scour formulas. Third, we present a novel theory for the temporal evolution of the scour depth during the developed phase (but with good prediction capabilities in the developing phase as well). By invoking the conservation of mass of sediment in the pothole, in addition to the energy conservation within the pothole and the phenomenological theory of turbulence, we obtain ordinary differential equations which we solve by numerical means. We validate the theory using our new and other datasets. Finally, we provide interesting interpretations of the scour process by using the results of the theory.

Hydraulic jumps, which frequently occur in hydraulic structures, have been extensively studied over the last century. However, only a few studies have evaluated hydraulic jumps in flows over rough beds and there are no studies that consider the air entrainment effect on conjugate depths. The current paper reports the results of an experimental investigation of hydraulic jump properties in flows over adverse-sloped rough beds, including the effect of air entrainment. Furthermore, a semi-theoretical predictive relationship is proposed to estimate jump characteristics for a wide range of hydraulic and geometric conditions covering both rough and smooth beds.

Block ramps or rock chutes are structures characterized by large bed slopes. They are increasingly used as river bed stabilization measures because of their particular capacity to sustain the river morphology and biological continuity. The scour process downstream of block ramps is an important research topic in engineering practice that must be controlled to ensure their structural stability. The purpose of this study is to analyze the scour downstream of a block ramp, in presence of a rock sill located in the stilling basin. The effect of sills is analyzed for non-uniform bed material. A dimensional analysis resulted in physically based dimensionless groups controlling the profile of the scour hole. The sediment distribution of the non-uniform bed mixtures at the scour equilibrium configuration is studied. The surface sediment redistribution is investigated for different scour typologies and the effect of protection work is also analyzed