Jet scour

This paper discusses scour without bed protection, such as propeller scour, two-dimensional horizontal, three-dimensional horizontal scour generated by free jets downstream of gates and outlets, two-dimensional vertical and three-dimensional vertical scour. The flow velocities in two- and three-dimensional propeller and free jets are briefly summarised where special attention is paid to the Dutch and German approaches for calculating the near-bed load caused by propellers. The time scale of propeller scour is approximated by applying the Breusers' time-dependent scour equation. For the maximum scour depth in the equilibrium phase Newton's second law is used