•Fire scenarios for a congested urban tunnel are examined.•An algorithm for assessing the fire safety level in a urban tunnel is proposed.•Individual histories of evacuees are visualized.•Some ...propositions of increasing the safety level in urban tunnels are provided.
A fire outbreak in a urban tunnel with congested traffic may pose a great danger to all tunnel users. The main threat to human life in an urban tunnel fire is thick toxic smoke quickly filling large parts of the tunnel. It hinders evacuation and may even lead to lethal intoxication. Due to the potentially rapid development of the fire, people trapped will need to evacuate on their own. Thus, tunnel safety systems must support their self-rescue efforts. In this paper, several scenarios of fire accidents in a real urban tunnel are numerically investigated. The scenarios differed in road traffic state, fire power and fire detection time. To make them realistic the entire sequence of events during a tunnel fire was numerically modeled. First, the formation of congestion is examined using VISSIM software, then fire development is simulated by Fire Dynamic Simulator and finally, the evacuation process is modeled by PATHFINDER software. All data needed to build these numerical models correspond to real conditions of the selected urban tunnel under the Martwa Wisła river in Gdansk (Poland). The outcomes of the work suggest the number of threatened people may be very large even under common circumstances. In the worst case over a half of people trapped inside may come into contact, at least temporarily, with factors threatening health or live.
Study on numerical modeling of jet fans Król, Aleksander; Król, Małgorzata
Tunnelling and underground space technology,
March 2018, 2018-03-00, 20180301, Letnik:
73
Journal Article
Recenzirano
•A brief review of commonly use fan models was presented.•Comprehensive study on jet fan modeling in Ansys Fluent was performed.•The results were compared with experimental measurements.•The ...advantages and disadvantages of each fan model are highlighted.•Some issues of the proper fan model selection were shown.
An overview of ways of jet fan modeling with the use of Ansys Fluent methods is presented. The theoretical models were built and validated basing on the experimental measurements made by Giesen et al. (2011). The results obtained with the all models were compared with this experimental data and next the detailed discussion was provided. A special attention was paid to the turbulence modeling, the range and the shape of the jet produced by the fan.
Ansys Fluent supports three suitable approaches allowing for accurate mapping of the axial fan operation, which differ in the degree of simplification of the reality. The first approach involves modeling a fan as a volume source of momentum. All three momentum components can be set, so the fan axis can be freely oriented in the space. The second approach involves modeling a fan with known characteristic. A fan is here a 3D object, but the fan rotor is a plane surface of zero thickness. The model is more accurate, but requires a set of parameters, which should be determined by the measurements. In the third approach a fan is also modeled as a 3D object, in this case the rotor has the real spatial dimensions. This model is capable to calculate all fan features by itself, but requires more computational resources. Apart from the above the fourth fan model as a velocity inlet is willingly used.
The selection of the model is dependent on data available and required minuteness of the fan representation and operation.
The article is an attempt to familiarise the readers with not only the source, Gustaw Zieliński’s Dzienniki mojego życia (Diaries of My Life), but also with the work on its first edition. Over a ...period of a few months (when these comments were noted down), the character of the text changed almost completely. One could even say that it transformed from a meticulously maintained personal text into a kind of notepad or sketchbook, which lost its diary-like character and became a sort of record of memories. The significance of this document, the range of themes discussed in it (among others, the literature, the social and cultural life of the first half of the 19th century) are all arguments in favour of taking up a laborious editorial work in order to publish this work. This article describes the stages of this work and discusses the ordering processes that make this source text interesting to a non-specialist reader.
•Full-scale experiments were carried out in a real road tunnel.•The airflow velocities were measured for two profiles.•Different fans operation modes were examined.•The natural caused airflow in the ...tunnel was numerically calculated.
The main aim of the research performed was to check the operation of a ventilation system in a conventionally operated road tunnel in Southern Poland. The length of the examined tunnel is 678m and it has a gradient of 4%. It includes longitudinal ventilation. The measurements of normal and reversed velocity of air flows (which were forced by the fans) were conducted at two cross-sectional profiles inside the tunnel. A set of fourteen thermal anemometers was applied there. In addition, at the intake and exit portals the wind direction, wind velocity and temperature were recorded during the tests. The fans worked according to the emergency operation pattern. The results were compared to estimated critical velocity and the correct functioning of the ventilation system was confirmed. The results showed a significant influence of the naturally caused airflows. Numerical simulations were performed to determine the air velocity resulting from this effect. CFD Ansys Fluent was used to solve the simplified model of the tunnel. The results confirmed that the combination of the stack effect and wind influence is crucial.
This work presents experimental and numerical research on the solar updraft at a tall building façade, which is 55 m high. The measurements are carried out in windless and cloudless weather, so the ...warmed by the solar irradiation façade is almost the only factor causing the buoyancy-driven airflow. A set of anemometers are used to record the vertical component of the air velocity. The mean value of the airflow velocity reached up to 2 m/s. However, the instantaneous value varied up to 4 m/s. A numerical model for the solar updraft is built using an ANSYS Fluent, and the temperature boundary condition at the façade is set based on a real IR image taken during the measurements. The numerical results are consistent with the experimental data and the theoretical considerations – at the upper façade edge, the total thickness of the buoyant plume is determined to be about 5 m, and the average airflow velocity is around 0.7 m/s. The strongly turbulent nature of the solar updraft is also confirmed.
•The airflow velocity for the solar updraft at a tall building façade was measured.•A numerical model of the solar updraft at a tall building façade was built.•A strong solar updraft was revealed, the average airflow velocity was over 2.5 m/s.
Stretching is one of the popular elements in physiotherapy and rehabilitation. When correctly guided, it can help minimize or slow down the disabling effects of chronic health conditions. Most ...likely, the benefits are associated with reducing inflammation; recent studies demonstrate that this effect from stretching is not just systemic but also local. In this review, we present the current body of knowledge on the anti-inflammatory properties of stretching at a molecular level. A total of 22 papers, focusing on anti-inflammatory and anti-cancer properties of stretching, have been selected and reviewed. We show the regulation of oxidative stress, the expression of pro- and anti-inflammatory genes and mediators, and remodeling of the extracellular matrix, expressed by changes in collagen and matrix metalloproteinases levels, in tissues subjected to stretching. We point out that a better understanding of the anti-inflammatory properties of stretching may result in increasing its importance in treatment and recovery from diseases such as osteoarthritis, systemic sclerosis, and cancer.
•Full-scale experiments were carried out in a real road tunnel.•The airflow velocities were measured for one cross-sectional profile.•The natural caused airflow and different fans operation modes ...were examined.•Theoretical considerations on natural caused airflow in the tunnel was presented.
This article presents the results of full-scale in situ measurements of airflow, conducted in a real-world road tunnel. The tunnel is located in Gdańsk city under one of the limbs of the Wisła river. The total length of the tunnel is 1378 m and the middle section of the tunnel is located at the deepest level. The inclination of the road is 3% and 4% for both directions from the deepest point. The tests covered measurements of airflow at 56 separate measuring points. The natural draught was determined, in addition to airflow rates for varying configurations of jet fan operation. The results were compared to those which were taken from automatic tolls mounted in the tunnel. The article also contains a theoretical discussion concerning a method for determining the natural draught in a tunnel.
The efficiency of tunnels systems is often evaluated using numerical simulations. This concerns both to normal and emergency mode of tunnel systems operation. Therefore the safety level of tunnel ...users may depend on the quality of numerical models being built. The most often studied areas cover the researches on natural and forced airflows in the normal mode and on fire development and smoke spreading in the emergency mode as well as modeling of fan operation. Thus, many software packages implementing Computational Fluid Dynamics (CFD) are applied here. Despite the available software is recognized as reliable, the problem arises because the built numerical models should be validated at least partially with experimental data. There is a shortage of experimental data from real tunnels due to high costs and many organizational or formal difficulties. Some researchers use data from scaled experiments, but this leads to problems connected with scaling. The paper presents the application of two widely used software packages—Fire Dynamics Simulator (FDS) and ANSYS Fluent to reproduce some scenarios of the operation of a tunnel ventilation system for normal and emergency mode. Most of results were compared with data obtained by own full scale measurements or data available in literature. Some practical issues concerning the application of FDS and ANSYS Fluent were discussed as well.
Hydrogen-blended natural gas has widely used in energy fuel systems in industrial and domestic applications. During storage, transportation and usage of the fuel, temperature characteristics make a ...key contribution to energy leak gas fire accidents. In this manuscript experimentally, the buoyant turbulent diffusion axial temperature profile of a hydrogenated methane jet fire is experimentally investigated under free fire and wall fire. Different hydrogen addition ratios, nozzle diameters, and fire heat release rates were considered in the experimental conditions. Temperature profiles and virtual origins were recorded and analyzed. It is found that the wall fire temperature is somewhat higher than that in the free fire at a fixed height. And the vertical temperature of the jet fire increases with the increase of the hydrogen addition ratio, while the flame height decreases. With the addition of hydrogen, the virtual origin is increased, and virtual origin of wall fire is clearly larger than that of the free fire. Due to the restriction of air entrainment from the sidewall and the hydrogen addition, the physical mechanism of restricted air entrainment was analyzed. In addition, a non-dimensional model of the virtual origin was proposed and analyzed for different conditions. Finally, the normalized vertical temperature profile in the continuous flame region, intermittent flame region and buoyant plume region based on the virtual origin and mirror-approach are still well characterized for air entrainment under all conditions. The results of this paper may demonstrate the potential for the risk assessment of hydrogen-blended natural gas fire.
Smoke management in the atrium with natural smoke venting is influenced by many parameters. These include the geometry of a building, external temperature and wind. The article presents the analyses ...of the impact of two wind speeds: 2.5 m/s and 7.5 m/s on conditions in the atrium. Volume flow rate of air inflowing to the atrium and the velocity of supply air in make-up air inlets were considered. The wind inflow from each direction was examined for two wind speed. This enabled the analyses of operation of particular make-up air inlets in variable external wind conditions. The possible impact of other buildings has been omitted. Moreover, the operation of exhaust openings was analysed. The subsequent step was examination of conditions in the atrium. The influence of wind, its speed and direction on soot mass fraction and its distribution in relation to the height of the atrium were considered. In addition, for some cases, visibility has been shown. It was proved that make-up air inlets located near the corner on the side wall parallel to the wind direction do not work properly, usually air flows through these openings to the outside. This allows to formulate guidelines for designers on the best locations of the inlet vents in buildings.
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