Seungsoo Lee

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.

Hyper-resolution 1D-2D urban flood modelling using LiDAR data and hybrid parallelization

Abstract Coupled 1D-2D modelling is a widely used approach to predict water movement in complicated surface and subsurface drainage systems in urban or peri-urban areas. In this study, a hybrid parallel code, H12, is developed for 1D-2D coupled urban flood modelling. Hybrid-1D-2D, or H12, enables street-resolving hyper-resolution simulation over a large area by combining Open Multi-Processing (OpenMP) and Message Passing Interface (MPI) parallelization. Variable grid sizing is adopted for detailed geometric representation of urban surfaces as well as efficient computation. To assess the capability of H12, simulation experiments were carried for the Johnson Creek Catchment (∼40u202fkm2) in Arlington, Texas. The LiDAR-derived digital elevation model (DEM) and detailed land cover map at 1-m resolution are used to represent the terrain and urban features in flood modelling. Hybrid parallelization achieves up to a 79-fold reduction in simulation time compared to the serial run and is more efficient than either OpenMP or MPI alone especially in hyper-resolution simulations.

Integrated 1D/2D Urban Inundation Modelling with Refined Grid and OpenMP Parallelization

Urban area consists of artificial structures such as buildings, roads, walls, parking lots etc. Therefore, the generation of fine meshes is a crucial component in depicting the complex urban features. However it accompanies huge amount of computational load with impractical calculation time. In this study, computational load reduction methods are tested using integrated 1D/2D urban inundation model based on refined grid with OpenMP parallelization technique. Refined grid (10 m with 5 m resolution) was able to reduce surface grid 2.47 times compared with regular grid (10 m resolution) and OpenMP parallelization shows 3.67 times running time reduction compared with serial code.