Some Effects of Suspended Sediment on Flow Characteristics

Abstract

Despite the steady advance in our knowledge of the mechanics of sediment transportation in the last two decades, there is still no theory that is completely satisfactory for engineering purposes. With present theories it is not possible accurately to predict the load under equilibrium conditions, and problems concerned with non-equilibrium conditions can hardly be treated at all because of their extreme difficulty. For instance, the elementary aspect of resistance to flow of a sediment-carrying stream is complicated by the fact that not only does the boundary configuration change with sediment transportation rate, but so does the internal turbulence, momentum transfer, and hence the shear. Once it is realized how long it has taken to bring the much simpler problem of resistance of clear fluids to the present state of knowledge, it is not surprising that progress on the sediment problem is not more rapid. The writer believes that progress with the transport problem will be made by studying the effects of sediment on the flow characteristics, since ultimately transport must be expressed in terms of the flow parameters. Accordingly, the present paper will attempt to clarify the nature of some of the effects of sediment on the transporting flows. Some unpublished data will be introduced and discussed along with published results.