Abstract

Results of a comparison between in-situ experiment and numerical modelling for flow around permeable pile groins were presented. The groin sets consisted of porous-fence piles with a diameter of 1.0 m and were conducted in the Laonong River, Southern Taiwan. A numerical model that solved depth-averaged RANS (Reynolds-averaged Navier-Stokes equations) and the continuity equation was developed to simulate the flow around the permeable pile groins. The turbulent effects were determined by the standard  turbulence model. Drag forces exerted by the flow on the permeable pile groins wereconsidered by adding source terms into momentum equations. The numerical predictions showed good agreement with the experimental results. The present model captured important flow features that were critical for characterizing the engineering design. Furthermore, the influence of different discharges on the hydrodynamic characteristics ofpermeable pile groins was investigated by using the present model. When the flow passed through the permeable pile groins, flow velocity reduced downstream of the groins and the water depth dropped significantly in the stream wise direction. It was observed that the levels of the flow velocity and water depth reduction decreased as the flow discharge increased. This was attributed to extra momentum transfer between the jet flows passing through the gaps between the permeable pile groins and the flow just behind the permeable pile groins.

Key words: Groins, shallow water, turbulent flow, numerical simulation.