Some E F F E C T S of Suspen D Ed Sedim Ent on Flow Characteristics

Despite the steady advance in our knowledge of the mechanics of sediment transportation in the last two decades, there is still no theory tha t is completely satisfactory for engineering purposes. W ith 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 re­ sistance to flow of a sediment-carrying stream is complicated by the fact that not only does the boundary configuration change with sedi­ ment transportation rate, bu t so does the internal turbulence, mo­ mentum 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 character­ istics, since ultimately transport must be expressed in terms of the flow parameters. Accordingly, the present paper will attem pt to clarify the nature of some of the effects of sediment on the trans­ porting flows. Some unpublished data will be introduced and dis­ cussed along with published results.