ENGELUNDS ANALYSIS OF TURBULENT ENERGY AND SUSPENDED-LOAD

We analyze a one-equation model for the turbulent kinetic energy of an open channel flow in the presence of suspension sediment. Engelund's pioneer analysis and his criterion for the threshold conditions for th e initiation of suspension are revisited, and it is concluded that suc h criterion does not represent any physical response of the system und er consideration, but rather appears to be an artifact of the mathemat ical manipulations of the turbulent energy equation. The present analy sis indicates that the effect of the suspended sediment on the turbule nt kinetic energy near the bed is to reduce such energy when the parti cle size is sufficiently small, and that the reduction increases with the sediment concentration and the particle settling velocity to flow shear velocity ratio. On the other hand, suspended particles of larger size can enhance the turbulence of the flow because of the production of turbulent kinetic energy through vortex shedding mechanisms. A cri terion is proposed to estimate the conditions for which turbulent enha ncement due to the presence of suspended sediment occurs.