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1. Experimental Study of Geysering in an Upstream Vertical Shaft

   https://doi.org/10.3390/w15091740  

   Allasia, Daniel G.; Böck, Liriane Élen; Vasconcelos, Jose G.; Pinto, Leandro C.; Tassi, Rutineia; Minetto, Bruna; Persch, Cristiano G.; Pachaly, Robson L. (May 2023, Water)

   Transient flows in stormwater systems can lead to damaging and dangerous operational conditions, as exemplified by geysering events created by the uncontrolled release of entrapped air pockets. Extreme rain and associated rapid inflows may result in air pocket entrapment, which causes significant changes in flow conditions and potentially geysering. Stormwater geysers have been studied in different experimental and numerical modeling studies, as well as from limited data gathered within real systems. However, there is still no complete understanding of geysering events, as stormwater system geometries vary considerably. Most past studies involved releasing air from an intermediate shaft, in which a significant fraction of the entrapped air may bypass the release. This work advances the understanding of geysering by considering uncontrolled air release through an upstream shaft or manhole. In such cases, the entire air pocket is released upon reaching the shaft, worsening the occurrence of geysering. Pressure and water level measurements were performed for various combinations of initial water pressure, trapped air pocket volume, and vertical shaft geometries, indicating the higher severity of these geysering events. The results obtained also corroborate previous studies in that the measured pressure heads were lower than the grade elevation. Future studies should include larger-scale testing and the representation of this geometry using CFD. 

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2. A virtual reality experiment on visual and auditory guidance for egress in road tunnel fires

   https://doi.org/10.1007/s10694-024-01668-9  

   Zhang, Yuxin; Kinateder, Max; Templeton, Anne; Warren, William H (November 2025, Fire Technology)

   Road tunnels are enclosed spaces that most occupants only experience while driving through them. In case of fire, however, occupants potentially need to evacuate on foot from a dangerous and unfamiliar environment. Clear and accurate guidance is important for an efficient and safe evacuation from tunnels. Common cues for evacuation guidance are a signage and audio messages that attract occupants to move on appropriate egress routes and avoid unsafe routes. This paper investigates how different types of visual and auditory signals influence occupants’ exit choices in a simulated tunnel evacuation. Common guidance cues were presented to participants in a mobile Head Mounted Display, and they were asked to choose between two possible exit doors in a simulated road tunnel. Two attracting cues (‘‘EXIT’’ signs, audio instructions), and two detracting cues (‘‘DO NOT ENTER’’ signs; traffic cones placed in front of an exit) were studied in three virtual reality (VR) experiments. In each experiment, the presence and direction of the cues were manipulated, and data from 20 participants were collected. Experiment 1 explored the effects of attracting cues, Experiment 2 detracting cues, and Experiment 3 the combination of attracting and detracting cues. Across all studies, participants tended to follow the guidance provided when there was only one cue. When several competing and even contradictory cues were present, participants were most likely to rely on audio instructions, followed by traffic cones and ‘‘DO NOT ENTER’’ signs, whereas ‘‘EXIT’’ signs were often disregarded. We conclude that participants tend to follow temporary cues that could carry current information, as opposed to permanently installed signage. Some corresponding suggestions are put forward on evacuation system design and strategic planning in a tunnel fire. 

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3. Tunnel structured manganese oxide nanowires as redox active electrodes for hybrid capacitive deionization

   https://doi.org/https://doi.org/10.1016/j.nanoen.2017.12.015  

   Byles, Bryan W.; Cullen, David A.; More, Karren L.; Pomerantseva, Ekaterina (January 2018, Nano energy)

   Hybrid capacitive deionization (HCDI), which combines a capacitive carbon electrode and a redox active electrode in a single device, has emerged as a promising method for water desalination, enabling higher ion removal capacity than devices containing two carbon electrodes. However, to date, the desalination performance of few redox active materials has been reported. For the first time, we present the electrochemical behavior of manganese oxide nanowires with four different tunnel crystal structures as faradaic electrodes in HCDI cells. Two of these phases are square tunnel structured manganese oxides, α-MnO2 and todorokite-MnO2. The other two phases have novel structures that cross-sectional scanning transmission electron microscopy analysis revealed to have ordered and disordered combinations of structural tunnels with different dimensions. The ion removal performance of the nanowires was evaluated not only in NaCl solution, which is traditionally used in laboratory experiments, but also in KCl and MgCl2 solutions, providing better understanding of the behavior of these materials for desalination of brackish water that contains multiple cation species. High ion removal capacities (as large as 27.8 mg g−1, 44.4 mg g−1, and 43.1 mg g−1 in NaCl, KCl, and MgCl2 solutions, respectively) and high ion removal rates (as large as 0.112 mg g−1 s−1, 0.165 mg g−1 s−1, and 0.164 mg g−1 s−1 in NaCl, KCl, and MgCl2 solutions, respectively) were achieved. By comparing ion removal capacity to structural tunnel size, it was found that smaller tunnels do not favor the removal of cations with larger hydrated radii, and more efficient removal of larger hydrated cations can be achieved by utilizing manganese oxides with larger structural tunnels. Extended HCDI cycling and ex situ X-ray diffraction analysis revealed the excellent stability of the manganese oxide electrodes in repeated ion removal/ion release cycles, and compositional analysis of the electrodes indicated that ion removal is achieved through both surface redox reactions and intercalation of ions into the structural tunnels. This work contributes to the understanding of the behavior of faradaic materials in electrochemical water desalination and elucidates the relationship between the electrode material crystal structure and the ion removal capacity/ion removal rate in various salt solutions. 

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4. Development of a fs/ps CARS system for temperature measurements in supersonic and hypersonic environments

   https://doi.org/10.2514/6.2024-2497  

   Stevenson, Anna; Dedic, Chloe E; Rodrigues, Neil S; Danehy, Paul M (January 2024, American Institute of Aeronautics and Astronautics)

   A hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) system was developed for quantitative measurements of temperature in a laboratory-scale supersonic jet facility. Measurements were recorded at low pressures and densities relevant for supersonic and hypersonic environments, with special interest in exploring the feasibility of deploying this technique in the 20-inch Mach 6 and 31-inch Mach 10 wind tunnels located at NASA Langley Research Center. Modifications to the existing supersonic jet facility were made to simulate a test section with a width of 31 inches, so that the size of the test section is relevant for either wind tunnel. The CARS system was designed such that a similar beam geometry can be used in the laboratory to acquire point-based fs/ps CARS measurements along two axes of translation. Rotational Raman transitions of O2 and N2 were targeted. 

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5. Solidity effects on the performance of vertical-axis wind turbines

   https://doi.org/10.1017/flo.2021.9  

   Miller, Mark A.; Duvvuri, Subrahmanyam; Hultmark, Marcus (January 2021, Flow)

   Abstract The variety of configurations for vertical-axis wind turbines (VAWTs) make the development of universal scaling relationships for even basic performance parameters difficult. Rotor geometry changes can be characterized using the concept of solidity, defined as the ratio of solid rotor area to the swept area. However, few studies have explored the effect of this parameter at full-scale conditions due to the challenge of matching both the non-dimensional rotational rate (or tip speed ratio) and scale (or Reynolds number) in conventional wind tunnels. In this study, experiments were conducted on a VAWT model using a specialized compressed-air wind tunnel where the density can be increased to over 200 times atmospheric air. The number of blades on the model was altered to explore how solidity affects performance while keeping other geometric parameters, such as the ratio of blade chord to rotor radius, the same. These data were collected at conditions relevant to the field-scale VAWT but in the controlled environment of the lab. For the three highest solidity rotors (using the most blades), performance was found to depend similarly on the Reynolds number, despite changes in rotational effects. This result has direct implications for the modelling and design of high-solidity field-scale VAWTs. 

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