The maintenance of the performance of sump pumps is important to mitigate flood damage in urban areas and lowlands. However, the air-entraining vortex in the sump leads to undesirable performance degradation. Thus, in this study, the newly designed floating anti-vortex device (F-AVD) was employed in the intake pipe to enhance the efficiency of water intake in the sump by decreasing the surface vortex. The performance of the F-AVD was evaluated from the model experiments, in which the sump model was designed to represent the pump station that operates in Korea. The flow in the sump was measured using the particle image velocimetry (PIV) technique, and the velocity and vorticity distributions were compared both with and without the adoption of the F-AVD. The experimental results indicated that the vortex structures behind the intake pipe were effectively mitigated by installing the F-AVD. The vorticity magnitude behind the intake pipe was reduced in range of 24.8–52.5% after the installation of the F-AVD. However, in the case of a flow rate increase, the efficiency of the F-AVD decreased because of the strong vortex. Thus, an additional anti-vortex device (AVD), which is attached to the backwall or the floor in the sump, is required to prevent the air entrainment in conditions with high flow rates.

Extreme rainfall causes surface runoff to flow towards lowlands and subterranean facilities, such as subway stations and buildings with underground spaces in densely packed urban areas. These facilities and areas are therefore vulnerable to catastrophic submergence. However, flood modeling of underground space has not yet been adequately studied because there are difficulties in reproducing the associated multiple horizontal layers connected with staircases or elevators. This study proposes a convenient approach to simulate underground inundation when two layers are connected. The main facet of this approach is to compute the flow flux passing through staircases in an upper layer and to transfer the equivalent quantity to a lower layer. This is defined as the ‘adaptive transfer method’. This method overcomes the limitations of 2D modeling by introducing layers connecting concepts to prevent large variations in mesh sizes caused by complicated underlying obstacles or local details. Consequently, this study aims to contribute to the numerical analysis of flow in inundated underground spaces with multiple floors.

Accurate flood risk assessment is useful for mitigating the hazards of dam break floods. Flood inundation may cause serious damage to human lives, property, and river environments. In many countries, flood risks are assessed to establish flood mitigation plans against unexpected flood events. Flood risk maps are based on inundation depth and maximum flow velocity obtained from numerical models based on shallow-water equations. Flood intensity, defined as the product of flood depth and velocity, is used to assess risk in vulnerable areas of many European countries. The inundation flow is affected by structures such as buildings and houses. In this study, changes in water depth, velocity, and flood intensity that are associated with arrangements of structures are numerically investigated. A numerical model is formulated using a finite volume approach and is first verified for available test problems. The effects of structures are then tested by measuring flood characteristics in an experimental basin in which various arrangements of model structures are placed. The measured flood characteristics are then compared to the numerical results.

Climate change has increased the damage caused by subtropical rainfall and typhoons in coastal areas. Major flooding factors in coastal areas can be classified as storm surges, river inundation, and inland submergence. Because previous studies usually applied a linear sum of individual inundation components to predict comprehensive flood phenomena, this approach does not consider weighted effects associated with the simultaneous occurrence of complex flooding. In this study, a series of comprehensive flood simulations were performed using two numerical models: HDM-2D and FLUval Modeling ENgine (FLUMEN). The results revealed that an integrated flood analysis considering the effects of inundation flooding, river flooding, and coastal flooding required evaluation of the risk of flooding in coastal cities.

In this study, a CUDA Fortran-based GPU-accelerated Laplace equation model was developed and applied to several cases. The Laplace equation is one of the equations that can physically analyze the groundwater flows, and is an equation that can provide analytical solutions. Such a numerical model requires a large amount of data to physically regenerate the flow with high accuracy, and requires computational time. These numerical models require a large amount of data to physically reproduce the flow with high accuracy and require computational time. As a way to shorten the computation time by applying CUDA technology, large-scale parallel computations were performed on the GPU, and a program was written to reduce the number of data transfers between the CPU and GPU. A GPU consists of many ALUs specialized in graphic processing, and can perform more concurrent computations than a CPU using multiple ALUs. The computation results of the GPU-accelerated model were compared with the analytical solution of the Laplace equation to verify the accuracy. The computation results of the GPU-accelerated Laplace equation model were in good agreement with the analytical solution. As the number of grids increased, the computational time of the GPU-accelerated model gradually reduced compared to the computational time of the CPU-based Laplace equation model. As a result, the computational time of the GPU-accelerated Laplace equation model was reduced by up to about 50 times.

A pump station is a crucial flood control facility for mitigating inundation of urban lowland areas. Securing a site to increase the capacity of a pump station or to maximize the discharge capacity of the pump sump in an urban area is difficult because of various limitations. Moreover, adding a facility to improve the pump capacity of a pump station may affect flow characteristics, e.g., unexpected increases in flow velocity and vorticity, and cause severe problems in pump station operation. To solve those problems, anti-vortex devices (AVDs) have been developed and adopted according to the appropriate design standards. The Korean design criteria for AVDs are based on experience and the standards of other countries because of the lack of adequate data on AVDs. In this study, flow in the sump was numerically simulated at various AVD heights to obtain data for improving the design and efficiency of a pump station. Consequently, the appropriate height for the AVD and changes in the flow pattern and vortex in the pump sump were determined and compared with 12 cases of inflow conditions with respect to the vertical location.