Performance of turbulence closure models for 3D RANS simulation of urban flooding with exchanges between flooded streets and building openings

Urban flooding poses significant risks to densely populated areas, necessitating
accurate predictive models for effective risk management. While 3D computational fluid
dynamics (CFD) models are increasingly used to simulate flood dynamics, the
selection of an appropriate turbulence closure model remains critical yet underexplored
in the context of urban flooding. This study evaluates the performance of three widely
used Reynolds-Averaged Navier-Stokes (RANS) turbulence models: standard k-ε, k-ω,
and k-ω SST, in simulating urban flooding in an idealized urban district model with flow
intrusion into buildings. Based on laboratory experiments reported in the literature, we
conducted three-dimensional simulations using OpenFOAM. Nine urban configurations
were considered, each with different opening layouts that allow flow intrusion into
buildings. The discharge distribution, surface flow patterns, and velocity fields at
selected cross-sections were analyzed. Results show that the simulated discharge
partitions match the measured values closely and lie within the ±1.5% uncertainty of
the experimental data with all three tested turbulence closures, demonstrating the
reliability of the numerical approach. In terms of surface flow and velocity
characteristics, the k-ε and k-ω SST models showed better agreement with
experimental observations than the k-ω model, particularly in capturing complex
surface structures, internal recirculation zones, and along-stream velocity
variations. This study provides insights into turbulence model selection for urban flood
simulations, particularly those involving flow intrusion into buildings. It constitutes a
useful reference for future urban flood modeling.