Instantaneous Stepwise-Steady CFD Model of BMP Response to Unsteady PM Loadings

• Published in: Journal of environmental engineering (New York, N.Y.) Vol. 139; no. 11; pp. 1350 - 1360
• Main Authors: Cho, Hwan Chul, Sansalone, John J
• Format: Journal Article
• Language: English
• Published: Reston, VA American Society of Civil Engineers 01.11.2013
• Subjects: Applied sciences; Best Management Practice; Chemical engineering; Computation; Computational fluid dynamics; Exact sciences and technology; Mathematical models; Natural water pollution; Particulate emissions; Pollution; Rainwaters, run off water and others; Steady flow; Technical Papers; Unsteady; Water treatment and pollution; Computational fluid dynamics; Steady flow; Rainfall; Hydrodynamics; Clarification; Runoff water; Modeling; Best Management Practice; Computational fluid dynamics technique; Unit operations; Clarifying; Rain; Loading; Runoff; Particulate matter; Stormwater management; Aerosols; Distribution function; Storm water; Separator
• ISSN: 0733-9372; 1943-7870
• DOI: 10.1061/(ASCE)EE.1943-7870.0000749

AbstractIn the last several years, computational fluid dynamics (CFD) has emerged as a potential tool to accurately predict the response of best management practices (BMPs) to highly unsteady rainfall-runoff (storm water) and particulate matter (PM) loadings. However, such predictive capability for BMPs as unit operation (UO) systems subject to highly unsteady loadings requires much higher computational time than for steady loadings. Therefore, to reduce computational time at a given level of predictive accuracy, an instantaneous response stepwise-steady method was tested to reproduce the unsteady load response of three geometrically different BMP UO systems. The units are baffled and screened hydrodynamic separator systems [(BHS) and (SHS)], respectively, as well as a granular media-based volumetric clarifying filter (VCF) system. The measured PM response was variable, a function of influent unsteadiness and the UO system geometry. Each hydrograph loading of a UO system was represented as a cumulative distribution function (CDF) which was discretized into a number of steady-flow steps using a discretization number (DN) for which an instantaneous response was modeled. DN was the model tuning parameter used to examine the stepwise-steady method. Despite variability in measured load-response for a UO system, a similar number of instantaneous response steady steps (DN of 35–40) were required to achieve a mean relative percent difference (RPD) of less than 10% between measured and modeled load response. For each UO system, the stepwise-steady method reduced computational time by an order of magnitude compared with a fully unsteady method.