Ruth Mossad

CFD study of the hydraulic performance of large-diameter gated fluming

AbstractThe hydraulic performance of large-diameter gated fluming, commonly used in furrow irrigation, was investigated using computational fluid dynamics (CFD). The continuity and the momentum equations governing the fluid in the system were solved numerically for a steady incompressible and turbulent flow using a realizable software model. The CFD results were compared with the laboratory measured results and those obtained using a hydraulic simulation model. The CFD results showed a good correlation with the measured data and those generated using the software. The velocity head in the pipeline had no influence on the magnitude of the outflows possibly due to the unique shape of the outlet. The pressure head recovery across the outlets was greater than the energy loss along the pipe; hence, the pressure and discharge increased towards the downstream end. The CFD approach was found to be an appropriate tool for detailed analysis of the hydraulic characteristics of gated irrigation pipelines.

Numerical prediction of the performance of horizontal sand filters as the pitch of the spiral protrusion changes

The height of vertical sand filters are limited due to their structural cost. A horizontal sand filter may offer a better alternative; however, flow channels to the least resistance zone generated at the top of the filter as the sand gets wet and settles. A horizontal sand filter, internally baffled with spiral protrusion, is numerically modelled to study the effect of these spirals in reducing the channelling and enhancing the filters effectiveness. Three different spiral pitches, 1.0, 0.75, and 0.5 m have been numerically modelled using Ansys FLUENT software. The parameters investigated were the power needed to run a flow rate through the horizontal filter and the residence time. The results show that as the spiral pitch decreases, the channelling reduces while the power increases. The power needed to pump a given flow rate of water in a 10 m long horizontal filter in all three cases investigated was less than the power needed to pump the same flow rate to the top of a 10 m long vertically standing sand filter. Results also showed that the time required for the flow to traverse through the sand filter increases in a nonlinear fashion as the pitch size decreases; however, the effectiveness of the filter increases.