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Dutta S.,University of Illinois at Urbana - Champaign | Tokyay T.E.,University of Illinois at Urbana - Champaign | Catano-Lopera Y.A.,CH2M HILL | Serafino S.,Metropolitan Water Reclamation District of Greater Chicago MWRDGC | Garcia M.H.,University of Illinois at Urbana - Champaign
Journal of Hydraulic Research | Year: 2014

The Terrence J. O'Brien Water Reclamation Plant (WRP) serves a population of around 1.3 million people and service area of 368.8 km2 in Chicago, IL. Metropolitan Water Reclamation District of Greater Chicago, the agency responsible for the maintenance and operation of the WRP, observed non-uniform distribution of grit deposition between the six grit tanks. Single- and multiphase flow simulations were used to investigate the non-uniform grit distribution and to evaluate potential solution alternatives to ensure the plant operates at an optimal capacity. The simulations revealed the formation of secondary currents due to a bend in the approach conduit; this explained the preferential sediment conveyance along the left side of the conduit and higher deposition at the southernmost grit tanks. Baffles at the centre of the approach conduit and a constriction wall along the left side were recommended for breaking the secondary currents and uniform distribution of the grits. © 2014 © 2014 International Association for Hydro-Environment Engineering and Research.

Catano-Lopera Y.A.,University of Illinois at Urbana - Champaign | Catano-Lopera Y.A.,Alden Research Laboratory | Tokyay T.E.,University of Illinois at Urbana - Champaign | Martin J.E.,University of Iowa | And 5 more authors.
Journal of Hydraulic Engineering | Year: 2014

Transient flow events can potentially damage infrastructure and threaten public safety in the vicinity of violent flow eruptions that occur where tunnel drop shafts interconnect with the surface-combined sewer system. Transient events have been observed in tunnels and at drop shafts in the tunnel and reservoir plan (TARP) system in Chicago on a number of occasions since operations first began in 1985. For the most part, the phenomenon has been controlled effectively by operating the system in a conservative mode through controlling the rate of filling. Nevertheless, more recently, not only water transients but also geysering events-the intermittent discharge of a combination of water and air from a hydraulic system-have occurred at the terminus of branch tunnels where controlled filling is not effective. The Metropolitan Water Reclamation District of Greater Chicago (MWRDGC), the operating agency for the system, has been prompted to develop engineering solutions to minimize transient flow occurrence and negative effects at the affected drop shaft locations. To this end, numerical modeling was conducted to investigate the cause and potential solutions. Such modeling included one-dimensional (1D) hydraulic transient modeling of a large domain in the system, followed by more detailed three-dimensional (3D) two-phase flow simulations within a smaller domain. The 1D approach revealed the interaction between localized events of interest and other transient flow features that originate far from the drop shaft under consideration. Computational fluid dynamics (CFD) modeling results show the complex interaction of trapped air and water in the tunnels. Even though more field observations are needed to test the accuracy of model predictions, careful interpretation of the results made it possible to pinpoint the problem and propose a solution. The findings also provided insight into the importance of considering both inertial instabilities as well as air-water interactions in geysering mechanics. © 2014 American Society of Civil Engineers.

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