Hydraulic Efficiency of Grate and Curb-Opening Inlets Under Clogging Effect

Abstract

The goal of this project is to investigate the hydraulic efficiencies of Type 13 (bar inlets), Type 16 (vane inlets), and Type R (curb-opening inlets) for street and roadway drainage. Although these inlets have been widely used in many metropolitan areas, the design empirical formulas and coefficients have not been verified. In this study, a flume was constructed in the laboratory to simulate street gutter flows ranging from 6 to 18 inch of flow depths. Type 13, 16, and curb-opening inlet models were built using a 1/3 scale to investigate the depth-flow relations under both on-grade and in-sump conditions. It was found that the flow interception capacity for a sump inlet is determined by either weir or orifice hydraulics, whichever is less for the given flow depth. Two new splash-velocity curves were developed to model the street gutter flow around a Type 13 or 16 inlet on a grade. In this study, a decay-based clogging factor was developed and recommended for the design of a series of inlets. The clogging effect shall be applied to the effective wetted length for an inlet that operates like a weir, or to the effective opening area for an inlet that operates like an orifice in a sump. In order to implement the results of this research, a new chapter of Inlet and Sewer Designs was introduced to the CDOT Hydraulic Design Manual. This design procedure has been coded into the design tool: UDINLET (MS Spread Sheet Model). Visit WWW.UDFCD.org to download.