Laboratory experiments and SPH modelling of hydraulic jumps

The formation of a hydraulic jump in a channel downstream of a spillway with developed upstream flow was investigated and reproduced using the SPH numerical model. The hydraulic jump is an important type of energy dissipation structure in hydraulic engineering. Such structures are subjected to considerable pressure fluctuations due to the dynamics of turbulence inside the hydraulic jump. The literature on the macroscopic features of the hydraulic jump is very extensive, but many characteristics of the internal flow phenomena remain unanswered. The hydraulic jump is a fascinating turbulent flow motion that remains poorly understood. The implemented numerical code was first tested using physical experiments on subcritical flow motion by Ben Meftah et al. (2007; 2008). In particular, it is applied to the modelling of an undular jump generated in a very large channel of the Coastal Engineering Laboratory of the Water Engineering and Chemistry Department of the Technical University of Bari (Italy). The undular jump is formed by low supercritical inflow Froude numbers, and is characterized by undulations of the water surface without a surface roller. The flow velocity and the free surface elevation measurements were taken using a two-dimensional Acoustic Doppler Velocimeter (ADV) and an ultrasonic profiler, respectively. SPH simulations were obtained by a pseudo-compressible XSPH scheme with pressure smoothing; eddy viscosity is evaluated through a mixing-length model depending on the distance from the channel bottom and from the free surface. The study made particular reference to the velocity and free surface profile with the aim of analysing the hydraulic jump development. The agreement between the numerical results and laboratory measurements was satisfactory.