An experimental and theoretical investigation of flow in a gross pollutant trap

摘要

Flow through a gross pollutant trap (GPT) with fully blocked screens is investigated experimentallynand theoretically using computational fluid dynamics (CFD). Due to the wide range of possiblenflow regimes, an experimental approach is developed which uses a downstream weirnarrangement to control the nature of the flow and the variation in free surface height. Tondetermine the overall flow structure, measurements are taken at a fixed depth throughout thentrap with an Acoustic Doppler Velocimeter (ADV), including velocity profile data across threencross sections of the GPT suitable for more detailed comparison with simulations. Observations onthe near-wall flow features at the free surface are also taken, due to their likely importance fornunderstanding litter capture and retention in the GPT. Complementary CFD modelling (usingnFluent 6.3) is performed using a two-dimensional k 2 1 turbulence model along with eithernstandard wall law boundary conditions or enhanced near-wall modelling approaches. Comparisonnwith experiments suggest that neither CFD modelling approach could be considered as clearlynsuperior to the other, despite the significant difference in near-wall mesh refinement andnmodelling that is involved. The experimental approach taken here is found useful to control thenflow regime in the GPT and further experiments are recommended to study a greater range ofnflow conditions.