CFD as a Complementary Tool to Benchmark Physical Testing of PM Separation by Unit Operations

Abstract

Unit operation (UO) systems have proliferated to sequester urban drainage particulate matter (PM) and PM-bound constituents. PM has been a primary focus of testing and certification. A nominal class of UOs, hydrodynamic separator (HS) systems require less area compared with nonproprietary UOs such as basins. Physical UO testing can be costly, with years to certification. Despite protocols, controlled certification tests are subject to variability, errors, and bias and could therefore be nonrepresentative, potentially negating accurate comparisons of results. Study objectives are to develop and then test computational fluid dynamics (CFD) models as a potential complementary tool for physical test–based UO certification programs. To facilitate this objective, publically available controlled physical tests of 21 HS systems and 154 test results based on two common certification programs are synthesized, and the variability examined. PM separation from two physical-validated CFD models are compared with the results synthesized from published certification reports. Synthesized results illustrate large variability across HS systems, up to 36.9%. Additionally, results of identical HS systems are inconsistent between certification programs, with a mean relative percent difference (MPRD) as high as 32.5%. In the CFD simulations of a physically tested full-scale HS system, Eulerian-equilibrium Eulerian (EE) and Eulerian-Lagrangian (EL) models reproduce PM separation with MRPD of 2.5% and 4.4%. In conclusion, simulations of publically reported HS systems illustrate the potential of CFD models as an adjuvant evaluation tool complementing physical testing. CFD models can also provide an efficient, economical, consistent, and revisable platform for UO systems.