Emptying of an initially water-filled horizontal PVC pipeline driven by different upstream compressed air pressures and with different outflow restriction conditions, with motion of an air-water front through the pressurized pipeline, is investigated experimentally. Simple numerical modeling is used to interpret the results, especially the observed additional shortening of the moving full water column due to formation of a stratified water-air “tail.” Measured discharges, water-level changes, and pressure variations along the pipeline during emptying are compared using control volume (CV) model results. The CV model solutions for a nonstratified case are shown to be delayed as compared with the actual measured changes of flow rate, pressure, and water level. But by considering water-column mass loss due to the water-air tail and residual motion, the calibrated CV model yields solutions that are qualitatively in good agreement with the experimental results. A key interpretation is that the long air...

Flood-resilient spatial planning in urban areas involves designing and implementing structural and nonstructural measures. For the latter, urban planners apply a precautionary principle, which is normally not grounded in the actual performance of the urban drainage system (UDS). This approach, however, fails during weather extremes with heavy precipitation. This paper presents a new concept for reducing pluvial flood risks in the urban planning process. The novelty of the developed planning support system named Extreme Weather Layer (EWL) is that it creates dynamic interlinkages between land developments, the performance of UDS, and other factors that contribute to flood risk. The EWL is built on the digital twin of the existing UDS and delivers an easy-to-use concept, where the end user can analyze hydraulic modelling results interlinked with climate scenarios using the GIS platform. This allows planning specialists to consider land use and soil types in the urban environment to simulate the response of the storm water system and the catchments to different rainfall events. This proposed approach was piloted in Haapsalu (Estonia) and Söderhamn (Sweden). The resulting planning support system, which performs as a set of layers within municipalities’ GIS, allows decision makers to understand and predict the impact of various spatial planning decisions on the pluvial flood risk.

Narrow-Band-Internet of Things (NB-IoT) is a promising wireless communication technology for harsh signal propagation conditions, including underground connectivity. The purpose of this study is to evaluate the real-life signal quality of an NB-IoT cellular sensor network for the monitoring and control of urban drainage systems. The implementation of the control systems toward smart infrastructures increase the need for low-cost and low-energy-consumption underground sensing devices. A measurement campaign was conducted in Rakvere, Estonia, to analyze the NB-IoT network's coverage and underground signal quality. The results were used to analyze the flood risk reduction potential in the pilot catchment, considering the quality of NB-IoT cellular network coverage. The signal measurements showed that in the case of plastic manholes, the best cellular transmitter placement is 0.5 m below the manhole cover, and at the ground level NB-RSRP reference signal strength of −104 dBm or better must be ensured to have a link budget with optimal energy consumption for communication. The results of flood risk reduction showed that excluding control locations with insufficient signal strength increased the number of major flooding nodes by 3.9% and mean flooding duration by 4.2% which is a relatively small change and characterizes the flexibility of the developed control system.

Smart urban drainage systems (SUDS) with real-time control are considered to be one of the prominent approaches to tackle the impact of climate change which results in heavy rainfall and floods in urban areas. However, the lack of reliable and efficient communication with sensors buried underground is considered as one of the main deficiencies preventing ubiquitous application of SUDS. With the recent developments of new noise insensitive technologies for ultra-narrow band (UNB) and chirp spread spectrum (CSS) communication, introducing new low-power long-range communication technologies (e.g. NB-IoT, LoRa), implementation of such drainage systems is becoming feasible. This paper presents a comparative study of NB-IoT and LoRa and evaluate the potential of these technologies to be used for SUDS. The study is conducted in different underground scenarios such as dry and damp conditions to highlight the potential benefits offered by LoRa and NB-IoT in terms of coverage, information rate, and energy consumption. It has been shown through the simulation results that NB-IoT offers capillary coverage with a high level of scalability as compared to LoRa. Furthermore, NB-IoT also provide high information rate and low energy consumption and is best suited for underground scenarios.

In many industrial applications the liquid trapped inside long pipelines can cause a number of problems. Intrusion of the pressurized air on top of the water column inside the horizontal pipeline can result in a less or more mixed stratified flow. The dynamics of a moving air–water front during the emptying of a PVC pipeline with the diameter-to-length ratio 1 : 1100 were experimentally and theoretically studied. In the experiments, the water was driven out of the pipeline with an initial upstream air pressure of 2 barg and a 4.5 m high downstream-end siphon, where the water outflow was restricted by a valve that was closed 11%. The measured discharges and water-level variations are analysed together with Control Volume modelling results. During the ‘forced’ (not only gravity-driven) emptying process, both the downstream-end drainage and tail leakage behind the moving air–water front decreased over the full water-column length. The water-column mass loss due to the tail leakage is referred to as holdup. The Zukoski dimensionless number is used to parameterize the relative shortening of the water column associated with the unidirectional movement of the air–water front along the large-scale horizontal test section of the pipeline, where surface-tension effects and minor losses at joints and turns are negligible.