Similarity in longitudinal decays of free jump and submerged hydraulic jump

Both free jump and submerged jump are of importance in practical engineering. The free jump is known to dissipate the kinetic energy most efficiently. The submerged jump, which is an alternative of the free jump, dissipates the kinetic energy over an elongated length of the roller with less pressure fluctuations on the bed. This study presents numerical simulations of hydraulic jumps of flows over an embankment-type weir to investigate the similarity of decaying flow structures for the free jump and submerged jump. The URANS equations are solved with the k-. SST turbulence model with the VOF method for computing the multiphase flow of air-water mixtures. The numerical model is validated against laboratory experiments, showing moderate agreement. Simulation results reveal that the mean velocity, turbulence intensity, and Reynolds stress for the free jump decay fast in the longitudinal direction compared with the submerged jump.