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

Abstract

Numerical models concerning inlet systems are run to assess the hydraulic performance of existing or new systems and estimate the flow interchanges between the surface overland and sewer flows. In most programs, these interactions are modelled using the orifice equation, with estimated discharge coefficients around 0.6. In this paper, discharge values and energy loss coefficients for several pressurized grated inlets were obtained by experimental and numerical approaches and compared. To achieve these goals, a numerical model replicating several experimental tests carried out at the hydraulic laboratory of Universitat Politècnica de Catalunya (UPC) was produced using a CFD model (Flow 3D). This numerical model was found to be highly sensitive to the mesh size used; however, it was able to accurately simulate the experimental processes. The comparison considered different combinations of pressurized flow though the grate, between 10 to 50 l/s, and different longitudinal gradients. The experimental discharge coefficient was found to increase with surcharging flowrate (ranging from 0.14 and 0.41), whereas the longitudinal gradient was found to have no effect. The discharge coefficients obtained in this study show that the standard 0.6 value commonly used by practitioners should be revised to a range between 0.14 to 0.41, depending on circulating flow and inlet type. In addition, the loss coefficient values range from 0.25 to 3.41.

Flood Risk in Urban Areas: Modelling, Management and Adaptation to Climate Change. A Review

“…In addition, even in cases where the sewer network is known in detail, comprehensive data on inlet locations are often missing or incomplete [145]. For this reason, many studies have focused on the numerical and experimental hydraulic characterization of drain inlets [150][151][152][153][154][155][156][157][158][159], as well as on the sensitivity of model results to the physical characteristics and location of inlets [97,145]. Inlet clogging due to a lack of maintenance and clearance has also been recognized as a major problem, indeed, one that can cause more flooding incidents than storm-sewer overloading does, especially in flat urban areas, leading to local flooding before the designed hydraulic capacity of the sewer network is reached [102,144,160].…”

Hydrodynamic Simulation of Urban Waterlogging Based on an Improved Vertical Flow Exchange Method

“…The determination of discharge coefficients for flow exchange equations over a range of hydraulic conditions and inlet types has a significant impact on the simulation results. Recent studies related to water exchange through manholes or inlets using the weir and orifice-type equations have been implemented using physical model experiments [22][23][24] and numerical simulations [25]. The values of the discharge coefficients are influenced by the inlet geometry and the approaching flow characteristics (flow depth and Froude number).…”

Study on the Head Loss of the Inlet Gradient Section of the Aqueduct

“…Cheng Yong et al [14] studied the three-dimensional flow at the open channel bifurcation by numerical simulation using FLOW-3D software, analyzed the hydraulic characteristics of the recirculation zone and flow structure near the open-channel bifurcation, and obtained the equations for the inflow width of the surface and bottom layers in a trapezoidal channel. Tellez-Alvarez, J et al [15] studied the energy loss coefficients of three types of grate. The energy losses recorded at flow rates between 20 L/s and 50 L/s ranged between 0.15 and 3.41, showing a negative correlation.…”