Jet scour

Abstract

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.

Editorial: Scour in the marine environment

“…The paper by Hoffmans and Verheij (2011) presents an overview of the state of knowledge on jet scour, based around current practice within the Netherlands. Jet scour has received more close attention in recent years due to the development of high-speed vessels and the interaction of their propulsion systems with port structures either during manoeuvring or while moored.…”

Over the dike top: modelling the hydraulic load of overtopping waves including transitions for dike cover erosion

“…Water collection in front of a height transitions with a vertical rise was observed during experiments that can lead to energy dissipation and dampening of the wave forces (Hoffmans and Verheij, 2011;Bakker et al, 2013). This was not (c) observed in the numerical model simulations, since only one overtopping wave is simulated and therefore no water of the previous overtopping wave is present.…”

“…The wall experiences high normal forces and pressures, that could lead to structural failure or erosion. On the other hand, water collects in front of the wall that can lead to energy dissipation and dampening of the wave forces (Hoffmans and Verheij, 2011;Bakker et al, 2013), and thereby reducing the load on the cover.…”

“…to account for the effect of turbulence on the scour erosion. This turbulence parameter is related to the depth-averaged relative turbulence intensity r 0 as (Jorissen and Vrijling, 1989;Hoffmans et al, 2009;Hoffmans and Verheij, 2011)…”

“…The additional load on the cover is often expressed as the energy dissipation of the flow indicated by a friction factor, for example in the case of high-velocity air-water flows over a grass cover or flow over stepped spillways (Felder and Chanson, 2015). The effect of bed friction is included in the GEM in the turbulence parameter, which originates from the local scour parameter that accounts for the effect of local turbulence on scour erosion created by both submerged and plunging jets (Jorissen and Vrijling, 1989;Hoffmans and Verheij, 2011;Hoffmans, 2012). The flow over a cliff at the damage shows similarities with both the flow over stepped spillways and a plunging jet and therefore the additional load by damages is included in the GEM using the turbulence parameter.…”