Veranstaltungsprogramm

The SWMM5+ finite-volume hydraulic solver for EPA SWMM was outlined at UDM 2018 and project updates were provided at UDM 2022. The public-domain open-source code for SWMM5+ was released in 2023 with the completion of US EPA funding. The code continues to undergo testing, debugging, and development by the project team. Recent work includes improvement of parallelization, a semi-implicit junction solver, equivalent orifice treatment of short conduits, and computation of air trapping. Foundations of the method, known issues, and plans for future development are discussed in this presentation.

For rapid prediction of urban flood that occurs within a short period of time from the onset of heavy rainfall, the use of GPUs is considered effective. For 1D-2D flood simulation based on the shallow water equations, CPU/GPU hybrid models, in which the sewer (1D) flow is solved by the CPU and the ground surface (2D) flow is done by the GPU, have been used in previous studies. However, a full GPU model that solves both 1D and 2D parts on the GPU has not been examined. In this study, we created the full GPU model and compared the computational speed with the hybrid model under various calculation conditions. In computational domains with varying the numbers of the 1D and the 2D cells, the full GPU model became up to about 7 times faster by increasing the number of the 1D cells and decreasing that of the 2D cells. In calculations for an actual urban drainage area, the full GPU model was able to complete calculations within the 5-minute delivery interval of rainfall forecast data, while the hybrid model took about 15 minutes. In addition, the calculated flood areas generally covered observed ones.

Culverts can become inadequate over time due to increasing flood peaks caused by higher-intensity rainfall events and urban development. Modifying the culvert inlet to increase discharge capacity can negate the need to rebuild the entire structure. Using Cradle CFD scFLOW Hexagon software for numerical modelling, this study found that box culverts with a 15° headwall and 15° wingwall increased the flow capacity by up to 34% at a headwater depth of twice the culvert opening (2D). This solution provides the best balance between hydraulic performance and practical implementation. The largest improvement obtained by rounding the edges of a square box culvert is 30%. A new flow improvement coefficient, C_TG, is proposed to quantify the improvement for each type of inlet, which can be used with existing design equations to calculate the improved discharge capacity for specific inlet modifications. Implementing inlet improvements for new and existing culverts will reduce flood risks and contribute to the climate resilience of road infrastructure.

Stormwater geysers erupting from manholes create hazards to urban infrastructure, public health, and safety during extreme storm events. Such geysers are the consequence of adverse multiphase flow interactions that conventional models, such as SWMM, do not capture. Most prior geyser studies have focused on local multiphase interactions using experiments or multi-dimensional computational fluid mechanics, which are difficult to scale up to large networks. Herein, a new method is developed that bridges the gap between detailed geyser representations and practical modelling constraints. This approach quantifies air entrapment in network segments based on the analysis of conduit geometry and inflow parameters. Air entrapment is a necessary precursor for geysers, so quantifying the entrapment potential provides a means of estimating geyser potential without requiring computation of the geyser physics itself. The method is applicable for a wide range of network configurations and provides a scalable tool for identifying geyser-prone areas, thus advancing large-scale urban stormwater management.

Urban flooding due to climate change-induced abnormal rainfall has caused recurring global damage, including in South Korea. One of the potential casualty causes is the dislodgement of manhole covers occurred by the lift of air-water mixture like geyser. To address this, the government mandated the installation of manhole fall prevention frames; however, it is hard to find standard designs or guidelines for such frames in the literature. This study utilized CFD to conduct four simulations based on flow rates from rainfall, ranging from minimum overflow conditions to extreme rainfall scenarios. Through these simulations, conditions were differentiated between manhole backflow causing the cover to open and a continuously closed state. These assumed conditions were then applied to different types of manhole fall prevention frames, where numerical analysis was performed to evaluate the stability and performance of each design. The results revealed that impact forces significantly increase under high-intensity rainfall, emphasizing the need for robust frame designs. This study recommends setting a minimum strength threshold of 4 kN to ensure the frame's reliability even under extreme conditions, such as an hourly rainfall of 60 mm. These findings provide critical insights for standardizing fall prevention frame designs and mitigating climate changerelated risks.

The discharge of combined sewer overflows (CSO) during rain events and the efficient operation of the sewer system can be a challenge for sewer network operators. Discharges into water bodies will probably have to be reduced even further in future due to new regulations. Long dry weather periods and deposits have a negative impact on the substance of sewer networks and shorten the lifetime of the infrastructure. Activating unused storage volume in the sewer can be an efficient and cost-effective alternative to building new storage volume. One possibility for predictive sewer maintenance can be the use of flushing waves from backed-up wastewater. Basically, sewer network control can utilize a lot of potential and help to overcome future challenges. This report from an application-oriented research project in the city of Jena shows the implementation and modelling of a modified floodgate in SWMM. The Results show the gained storage volume, the reduction of combined sewer discharge and flushing velocities for possible sewer flushing.