•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.
Recovery and recycling end-of-life tires (ELT) incur a significant cost of collection and transportation. Improperly conducted ELT collection contributes to excessive vehicle exhaust emissions and ...high transportation costs. This study investigates the collection and transportation costs of ELT including preliminary processing of waste tires like cutting, baling and packing tires to reduce the volume of each shipment. Waste collection vehicles exhaust emissions were examined in the collection scenarios. In this study a novel approach of multi-criteria decision support – coupled analytical hierarchy process (AHP) and Preference Ranking Organization METHod for Enrichment of Evaluations (PROMETHEE) methods have been applied for selecting the best scenario, considering costs and environmental impacts in the collection of ELT. The results show the most profitable method of the ELT collection by routing of heavy truck and pickup of waste tires from a local network after preprocessing. Packing the tires in the collection points reduces the total cost between 20-30% and vehicles’ exhaust emissions up to 40 %, compared to other methods in the Polish case study. The proposed decision support method is useful for evaluating environmental and cost factors, especially in regions where transport costs due to distances constitute the largest share of costs. This method and the results are useful for the ELT collection companies in promoting sustainable methods of transportation of waste including emission and economic factors. The study encourages using the compacting of ELT at the collection points for more efficient transportation.
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.
The issue of airflow dynamic in a road tunnel is considered in this study and its impact on smoke management and people safety is highlighted. It was an attempt to estimate the time needed to reach a ...final steady state of airflow when the operation mode of jet fans was switched. The numerical model of the tunnel was solved with the use of Ansys Fluent. To reproduce the decrease of atmospheric pressure with height, relative static pressure was applied using UDF (User Defined Function). The ambient weather conditions were taken into account as well. The wind influence was introduced by the additional component of dynamic pressure applied against one of the tunnel portals also using UDF. There are some theoretical foundations of airflow in a tunnel presented in this paper. The obtained results were compared with the measurements carried out in a real road tunnel and the results obtained while applying the above-mentioned physical model. The main contribution of the presented work is the indication of a relatively high relaxation time of airflow in a tunnel, which could be important when designing the emergency pattern of a ventilation system. Additionally, some considerations of kinetic energy exchange between fan jet and air volume would be helpful when choosing fans for ventilation systems being designed.
The main objective of this research was to examine the development of fire in a furnished room in a typical high-rise building. This work was part of research on the fire safety of building ...occupants. It included two controlled fires in which a standard sofa in a room was set on fire. Several thermocouple trees were arranged in the test room and the temperature was continuously recorded. Additionally, each fire test was videotaped for further analysis. Since an unexpected forepeak of the temperature course was observed, special attention was paid to explain this phenomenon. For this purpose, numerical models of fire development in a furnished room were built using the well-recognized software package, ANSYS Fluent and Fire Dynamic Simulator (FDS). The numerical research was focused on fire spread over a single piece of furniture, the sofa. The data recorded in real experiments were used to tune and validate the numerical models. The results of the Fluent numerical simulation were consistent with the recorded experimental data and proved that after the initial growth, there was a critical phase of fire development in which the fire might almost snuff or flare again. Meanwhile, the FDS results, despite being generally in accordance with the experiment, did not reproduce this critical phase of fire spreading.
This paper presents the results of hot smoke tests, which were conducted in a real road tunnel. The tunnel is located within the expressway S69 in southern Poland between cities Żywiec and Zwardoń. ...Its common name is Laliki tunnel. It is a bidirectional non-urban tunnel. The length of the tunnel is 678 m and it is inclined by 4%. It is equipped with the longitudinal ventilation system. Two hot smoke tests have been carried out according to Australian Standard AS 4391-1999. Hot smoke tests corresponded to a Heat Release Rate (HRR) equal to respectively 750 kW and 1500 kW. The fire source was located in the middle of the road lane imitating an initial phase of a car fire (respectively 150 m and 265 m from S portal). The temperature distribution was recorded during both tests using a set of fourteen thermocouples that were mounted at two stand poles located at the main axis of the tunnel on windward. The stand poles were placed at distances of 5 m and 10 m. The recorded data were applied to validate a numerical model, which was built and solved using Ansys Fluent. The calculated temperature distribution matched the measured values.
This paper presents the results of numerical experiments on fire development and the backdraft phenomenon. The numerical model of fire development built with the use of Ansys Fluent was then ...validated based on literature data taken from real fire experiments. Some theoretical foundations of airflow and combustion modelling were added. Some features of the numerical model, which allowed for its high accuracy to be achieved, were widely discussed. Since large buoyancy forces were involved, to reproduce the decrease of the atmospheric pressure with height, a variable static pressure was applied using UDF (user-defined function).The results showed good accordance taking into account both the temperature profiles and the distribution of the airflow velocity. Once the model was validated, the research was extended to examine the backdraft phenomenon. The results revealed characteristic phases of the phenomenon and the occurrence of the gravity current as well, which were reported by empirical experiments.
The process of planning the metro system is very complex. This is due to the large amount of required input data originating from many domains. Additionally, the required extraordinary budget makes ...the design phase difficult and forces some trade-offs to meet most expectations. Designing a metro system requires often a multi-variant analysis to examine possible future ways of urban agglomeration development. In such circumstances there is a need to apply an efficient method, which allows for obtaining a draft design of a metro system. This paper presents an application of a genetic algorithm for two stages of a metro system design. The first stage determines the layout of metro stations, which optimally meets the transportations demands of the inhabitants. The second stage generates the optimal topology of lines connecting the stations, taking into account the minimization of construction costs and the total travel time of all passengers. The parameters, which control the operation of the optimization procedures, were tuned with the use of the Taguchi method.
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.
Numerical analysis of fire development in a closed compartment was carried out. Three cases were analyzed: a compartment with one, two and three ventilation openings. The influence of the number of ...ventilation openings on indoor conditions was investigated. The distributions of temperature, of mass fraction of O
,CO
also well the flow rate through the bottom opening were considered. Analyses have shown that only three ventilation openings in the compartment give the balanced conditions. This means that the outside air is supplied with the bottom opening and the hot smoke is removed with the upper openings. The research also allowed to look at the conditions prevailing in the room during the development of the underventilated fire. The Ansys Fluent program was used to solve the numerical model. In addition, the User Defined Functions (UDF) were used for numerical analyzes. It allowed for modeling the dependence of air pressure in the ventilation openings on the height.
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