Computer-Aided Design of Diffusers on Marine Outfall System

Abstract

In this study, computer-aided design of marine discharge diffusers is investigated from aspect of dilution and wave effects due to external flow, internal hydraulic flow analysis and mechanical analysis including thin-thick walled steel-pipe stress analysis and local bucklings and buckling propagations. Waste water discharges must be analyzed by near field, far field and bacterial thinning with cloud heights. Finally, the feasible diffuser geometry due to internal and external flow is determined by assigning the certain diameter required hydraulically for discharge, providing the required specifications for dilution and obtaining the required pipe thicknesses from steel pipe structural analysis. The considered pipe diffuser system is especially laid freely at sea bottom. At the beginning of the study, the main principles of fluid mechanics were guiding. Internal pipe pressures, velocities and reaction forces due to the hydrodynamic external pressures at the end of port diffusers are calculated by basic principles of fluid mechanics considering steady-state flow. External forces generated from waves are also calculated by using the Linear wave theory. Under these external and internal forces, the pipe stability and strength are carried out in terms of jets, plumes and microorganism concentration due to effluent dilution are discharged horizontally and vertically. Finally, the DIffuser Pipe-DESIGN (DIP-DESIGN) software developed in the scope of this study, provides many advantages in designing diffusers with considering the external and internal flow conditions, specifications of dilution and pipe size and geometry requirements and has been run on a illustative example.