Control Effect of Flow through Perforated Inlet Diffuser in the Rectangular Settling Tanks : I. Theoretical Considerations

Abstract

In this paper, flow behaviour in the controlled inlet chamber of a rectangular settling tank are analysed two-dimensionally considering the lateral outflow through the perforated diffuser wall, and the effect of flow training or regulation by that type of diffuser are discussed in detail. In the case where the direction of the inflow is parallel to the diffuser wall, the distribution characteristics of the rate of discharge at the outer side of the diffuser seem similar to those for flow through a uniformly perforated pipe, a case which was previously analysed by one of the authors, and resulted in a flow with the tendency to turn aside towards the far end of the side wall. When the direction of inflow is perpendicular to the diffuser wall, a circulation of large scale occurs in the inlet zone upstream of the diffuser wall, and the velocity distribution along the diffuser wall shows very delicate changes. These results depend on numerical calculations based on an anylysis in which the viscosity is neglected and some other practical approximations are made.