Design and hydrodynamic performance testing of a new pressure sand filter diffuser plate using numerical simulation

Abstract

Sand filters are widely used for treating irrigation water. Their technical development maximises their operational efficiency. Using numerical simulation techniques, such as computational fluid dynamics (CFD) can provide a better understanding of the processes associated with fluid flow. This study aimed to design, build and evaluate the hydrodynamic performance of a sand filter diffuser plate using numerical simulations. The objective was to maximise hydrodynamic efficiency during the filtration process and consequently minimising the effects of flow on the sand bed surface. The numerical simulations and laboratory tests were divided into two parts. Firstly, the hydrodynamic flow profile in three different sand filter diffuser plates was established using three commercial filters available in Brazil. Secondly a new model of sand filter diffuser plate was designed and evaluated. The simulations predicted the flow pattern of sand filters for the test conditions. For the three commercial diffuser plates and flow velocities evaluated, a tendency to generate a vortex and a tangential flow on the sand bed surface was observed. This resulted in sand movement inside the equipment with the formation of accumulation points and creation of preferred paths for water and suspended solids. The new model showed reduced internal flow kinetic energy and vortex formation. Consequently there was increased flow uniformity in the sand bed surface with reduced deformation of the bed.