Advances in the characterization of pressures and velocities in the overtopping of arch and gravity dams

When dams overflow, they produce free jets that discharge into plunge pool basins. The pressure and velocity distributions of the flow in the plunge pool must be estimated to evaluate the potential scour that might destabilize the dam. In Protections 2016 event (Fort Collins, Colorado, USA), the first two authors presented results of free falling jets in plunge pool, comparing numerical results against experimental data. Instantaneous pressures, velocities and air entrainment were obtained with piezoresistive transducers, Acoustic Doppler Velocimeter and optical fiber, respectively. To identify the level of reliability of models, numerical simulations were carried out by using the “homogeneous” model of ANSYS CFX, together with different turbulence closures. Castillo et al. (2015) established different equations to calculate the jet energy dissipation in the air and in the water cushion, as a function of the Y/Bj and H/Lb ratios (where Y and H denote the depth of the water cushion at the plunge pool and the total head, respectively, and Lb is the break-up length). This paper includes further measurements that complete the range of flow tested. New adjustments and analysis are presented in the mean, fluctuating and extreme dynamic pressure coefficients. Furthermore, velocity and turbulent kinetic energy profiles have been obtained. The energy dissipation in the air and in the plunge pool has been also analyzed