Author(s): Seung Oh Lee; Terry W. Sturm; Yong-Sik Cho; Jin-Woo Lee
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Keywords: Hydraulic model; Numerical simulation; Oil- grit separator; Turbulence; Urban stormwater management; Water quality
Abstract: This study presents the results of a comprehensive experimental and computational investigation of the three-dimensional turbulent flow structure in a n oil- grit separator used for urban stormwater treatment. Such structures are designed to trap oil and grit in urban runoff from small impervious areas during a moderate rainfall. Their performance is not well established because of different design configurations of internal baffles used by various manufacturers. Experimental runs in a 1: 2 scale model were conducted in the Hydraulics Laboratory at the Georgia Institute of Technology, Atlanta, GA to assess the performance of an existing oil- grit separator design and to suggest design modifications to improve its performance measured as trap efficiency. An acoustic Doppler velocimeter (ADV) was used to measure the point velocit ies and turbulence characteristics of the flow domain in the oilgrit separator. Computational investigations were implemented through the use of a commercial software package, FLOW-3D, which employs the volume of fluid method (VOF) and the fractional area-volume obstacle representation (FAVOR) method. The VOF method is utilized to track the free surface configuration while the FAVOR method models solid objects within the flow domain. The Reynolds-averaged Navier-Stokes equations were solved e-k using the standard turbulence model and law-o f- the-wall formulation. It was found that the comparison between experimental and numerical results for the three-dimensional velocity vectors showed good agreement in this study. Both experimental and numerical results revealed the fundamental interaction of the turbulent flow structures in the oil- grit separator and established the basis for improving the performance of the oil- grit separator in terms of trap efficiency. This suggests that the numerical flow model can be used to screen various designs before selecting a smaller number of internal baffle-plate configurations to test in physical model studies.
Year: 2007