Validation of 2D shock capturing flood models around a surcharging manhole

Abstract

This work offers a detailed validation of finite volume (FV) flood models in the case where horizontal floodplain flow is affected by sewer surcharge flow via a manhole. The FV numerical solution of the 2D shallow water equations is considered based on two approximate Riemann solvers, HLLC and Roe, on both quadrilateral structured and triangular unstructured mesh-types. The models are validated against a high resolution experimental data-set obtained using a physical model of a sewer system linked to a floodplain via a manhole. It was verified that the sensitivity of the models is inversely proportional to the surcharged flow/surface inflow ratio, and therefore requires more calibration from the user especially when concerned with localised modelling of sewer-to-floodplain flow. Our findings provide novel evidence that shock capturing FV-based flood models are applicable to simulate localised sewer-to-floodplain flow interaction.

On the Characteristics of Velocities Fields in the Vicinity of Manhole Inlet Grates During Flood Events

“…The mesh was tailored to each grate and a finer mesh was used where required to improve the accuracy of the model diminishing the small differences between meshes. The maximum edge size for the mesh was based on previous studies (Martins, Kesserwani, et al, ; Rubinato et al, ) being 0.002 m inside the manhole area ( r < 0.12 m), 0.01 m in the outer circle (0.12 m < r < 0.24 m), and 0.025 m in four rectangles going each positive and negative Cartesian direction with length 0.545 m and width 0.24 m (Figure ). Outside of these areas the maximum edge is of 0.2 m and transition between each maximum edge size is made using a growth rate of 0.05 using NETGEN algorithm (Schöberl, ).…”

“…Studies on linkage systems are usually focused on experimental facilities with emphasis on the efficiency (Bock et al, ; Gómez & Russo, ; Gómez & Russo, ; Li, Geyer, et al, ; Li, Sorteberg, et al, ; Li et al, , ; Martins et al, ; Russo et al, ) or the use of fully 3‐D CFD models to study the characteristics of the flow inside the manhole (Djordjevic et al, ; Leandro et al, ; Lopes et al, , ). Studies that verify the applicability of 2‐D models to directly reproduce drainage flows and flow conditions close to the linkage structure on the floodplain during flood events are however scarce (Martins, Kesserwani, et al, ; Rubinato et al, ), and proper validation is usually focused on the bed elevation (Cea et al, ) far from the interface structures.…”

Integrated modelling of overland flows and drainage networks in a urban environment

“…S. Chen et al (2007) propose to calculate the flow interchange between the two models by using weir or orifice equations. This solution has been use by other authors (A. S. Chen et al, 2015;Leandro and Martins, 2016;Martins et al, 2017;Seyoum et al, 2012). Its ability to adequately reproduce actual physical processes has been proven by comparing by physical experiments (Hakiel and Szydłowski, 2017;Rubinato et al, 2017).…”

“…where Q e is the volumetric exchange flow being positive when leaving the drainage, d 2d the water depth in the surface cell, A cell the raster cell area and ∆t 1D the time-step of the drainage model. For further stability, Martins et al (2017) propose an additional flow limiter when the flow exits the drainage model. This flow limiter has an high impact on the calculated flow rate, and is used to mitigate limited observed instabilities.…”

“…This flow limiter has an high impact on the calculated flow rate, and is used to mitigate limited observed instabilities. Therefore, Itzï does not implement that additional flow limiter proposed by Martins et al (2017). However, Itzï is set to use by default the orifice and weirs coefficients obtained from physical experiments by Rubinato et al (2017).…”