Quantification of Energy Loss in Two Grated Inlets under Pressure

Abstract

Grated inlets have the normal function of collecting the surface runoff into sewer networks, but when the flow exceeds the capacity of the sewer pipes and conduits get pressurized, an outflow from the sewer manholes and grates can occur. In this case, the grate produces an energy loss in the outflow from sewer to street that could be hydraulically quantified characterizing this kind of flow. Energy loss analysis in trash racks can be found in technical literature, but no specific studies on sewer grate inlets have been found. For this reason, some experiments in full scale were developed in the hydraulic laboratory of the Technical University of Catalonia (UPC) in order to quantify hydraulic energy losses associated with flow through grated inlets during surcharging conditions. The main goal of this research work was to experimentally quantify the values of the local loss coefficient k for two different surcharged real scale grated inlets existing in Barcelona. For the tested overflows between 20 and 50 L/s, a range from 0.25 to 3.41 was observed for k coefficients under different average velocities of reference and different flow conditions.

Numerical and Experimental Approaches to Estimate Discharge Coefficients and Energy Loss Coefficients in Pressurized Grated Inlets

“…Both grates, along with grate 3, were used for the numerical simulation in Flow 3D. Grates were examined previously in [14,15,52], and grate 2 was tested during the period of internship of Amezaga-Kutija [53].…”

“…Both grates, along with grate 3, were used for the numerical simulation in Flow 201 3D. Grates were examined previously in [14,15,52], and grate 2 was tested during the pe-202 riod of internship of Amezaga-Kutija [53]. with a width of 3 m and a total length of 5.5 m, where a single inlet can be tested (Figure 1).…”

“…Both grates, along with grate 3, were used for the numerical simulation in Flow 3D. Grates were examined previously in [14,15,52], and grate 2 was tested during the period of internship of Amezaga-Kutija [53]. The platform has the potential to be tilted in both the longitudinal direction (0-10%) as well as in the transverse direction (0-4%).…”

“…Within this framework, 1D/2D coupled models are able to simulate at the same time 2D overland flow and 1D sewer flow, with the related links and flow interchanges through manholes and inlets [9][10][11]. In these models it is necessary to characterize the hydraulic performance of inlet systems in terms of hydraulic efficiency and to determine specific coefficients like discharge coefficients or energy losses coefficients in case of free or surcharged sewer flow conditions [12][13][14][15][16].…”

“…Modification of the experimental platform located in the Laboratory of Hydraulics of the Technical University of Catalonia (UPC) allowed us to study the surcharging conditions of the grate inlet [14,15,51].…”