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The pulmonary circulation is a low-pressure, low-resistance circuit whose primary function is to deliver deoxygenated blood to, and oxygenated blood from, the pulmonary capillary bed enabling gas exchange. The distribution of pulmonary blood flow is regulated by several factors including effects of vascular branching structure, large-scale forces related to gravity, and finer scale factors related to local control. Hypoxic pulmonary vasoconstriction is one such important regulatory mechanism. In the face of local hypoxia, vascular smooth muscle constriction of precapillary arterioles increases local resistance by up to 250%. This has the effect of diverting blood toward better oxygenated regions of the lung and optimizing ventilation–perfusion matching. However, in the face of global hypoxia, the net effect is an increase in pulmonary arterial pressure and vascular resistance. Pulmonary vascular resistance describes the flow-resistive properties of the pulmonary circulation and arises from both precapillary and postcapillary resistances. The pulmonary circulation is also distensible in response to an increase in transmural pressure and this distention, in addition to recruitment, moderates pulmonary arterial pressure and vascular resistance. This article reviews the physiology of the pulmonary vasculature and briefly discusses how this physiology is altered by common circumstances. [ABSTRACT FROM AUTHOR]

Compartment fire is an important research area in fire science and fire safety. Owing to its simplicity, the zone model remains attractive in studying compartment fire. Although computer software packages for the two‐layer zone are in popular use, a basic understanding of the physical phenomena involved and the mathematical formulation thereon would benefit users of the zone model in terms of critical judgement of software outputs, which could be unreasonable, and insight of the general trends of important variables. In general, the differential equations based on a two‐layer zone model have no analytical solutions and numerical methods are required. However, stiffness is present in using numerical methods to solve these differential equations, and reliable results are obtained only when very small time steps are used in computation. Nevertheless, in some special cases, analytical solution for the clear height in the zone model exists, as demonstrated in the present study. Predicted values of smoke layer height in the present approach are shown to be in good agreement with experimental results reported in the literature. The present work would provide insight into the tenability condition of a compartment on fire and is an important issue in fire safety management. [ABSTRACT FROM AUTHOR]

Probabilistic fire simulation has been gaining interest in performance-based design approach. Very few evaluations on modelling performance can lead to unnecessary simulations which limit the understanding of fire engineering practitioners to select suitable model for a specific fire phenomenon. This study presents comparison of models' capabilities to recreate kitchen fire experiment through probabilistic assessments when there are various possibilities of fire spread can occur within the compartment. Such situation must consider the possible heat release rate curve from previously burning kitchen item, as this will effect on the possibility that other item igniting, and so enhance the intensity of fire. Determination of accumulated heat release rate data is assessed through the use of B-RISK and simplified model. Simulation input employs design fire for single furniture that was characterized through combination of peak growth and exponential decay functions using statistical analysis of fire severity characteristics from collated experimental data. Probabilistic correlation discloses that both models are able to produce results within an acceptable range of fire practice (> 20%), but B-RISK has better representation of possible cumulative heat release rate region than simplified model when more than 58% similarity of fire spread predictions among multiple items is achieved over different boundary ranges. [ABSTRACT FROM AUTHOR]

Featured Application: The proposed approach could be used as a basis for a decision support tool to reduce the risk of fire in large multi-compartment structures. This paper proposes a hybrid multiscale approach to evaluate the fire performance of large multicompartment structures. A probabilistic network model is at the core of the proposed approach, whose inputs, namely the mean durations of the fire phases and fire transmission through the barriers between compartments (e.g., walls or ventilation ducts), are determined beforehand by a zone model, which is detailed in a companion paper and a one-dimensional computational fluid dynamics code. Next, a proof of concept is developed by applying the hybrid approach to different fire scenarios in a full-scale generic military corvette and a four-story office building. The simulation results highlight the strengths and limitations of the proposed approach. Regarding the latter, a field model is used to evaluate how the hybrid approach performs depending on the interaction between the entire building system and its ventilation and the fire. Finally, a statistical study is carried out to produce fire vulnerability and risk maps, ranking the fire compartments according to their vulnerability or propensity to generate serious fires. [ABSTRACT FROM AUTHOR]

Dispersion and natural ventilation of hydrogen leaked at the floor center of a confined space are analytically and numerically studied in this contribution. Two symmetrical openings located atop two opposite walls and several sets of partition boards with varying heights, 0–1.0 m with 0.2 m increment, mounted under the ceiling were designed to examine their effects on ventilation efficiency. Without partition boards, a semi-analytical model combining a modified buoyancy ceiling jet theory and zone model was established to predict the key parameters at steady stage. The analytical predictions were compared with numerical results. 15 monitors were predesigned at an opening and the channels separated by the partition boards to collect the velocity and hydrogen concentration evolutions. The results show that the existence of the partition boards significantly promotes the ventilation efficiency by decreasing the hydrogen concentration in the confined space, constraining the flammable regime into a smaller volume, and increasing both the inflow and outflow velocities. Better ventilation efficiency is achieved by higher partition boards until a critical height after which no appreciable improvement can be gained. Applying the partition boards considerably shortens the developing stage of the dispersion process and intensifies the turbulence of outflow. Conclusions obtained in current work may benefit the natural ventilation system and building structure design for hydrogen safety in practical applications. • Impact of partition boards on ventilation efficiency of hydrogen is studied. • A buoyancy ceiling jet of hydrogen is modified from a thermal-driven ceiling jet. • A semi-analytical model is proposed to predict the stratification at steady stage. • Better ventilation efficiency is achieved by higher partition boards. • Flammable gas is restrained into a smaller volume after applying partition boards. [ABSTRACT FROM AUTHOR]

This paper proposes a hybrid multiscale approach to evaluate the fire performance of large multicompartment structures. A probabilistic network model is at the core of the proposed approach, whose inputs, namely the mean durations of the fire phases and fire transmission through the barriers between compartments (e.g., walls or ventilation ducts), are determined beforehand by a zone model, which is detailed in a companion paper and a one-dimensional computational fluid dynamics code. Next, a proof of concept is developed by applying the hybrid approach to different fire scenarios in a full-scale generic military corvette and a four-story office building. The simulation results highlight the strengths and limitations of the proposed approach. Regarding the latter, a field model is used to evaluate how the hybrid approach performs depending on the interaction between the entire building system and its ventilation and the fire. Finally, a statistical study is carried out to produce fire vulnerability and risk maps, ranking the fire compartments according to their vulnerability or propensity to generate serious fires.

This contribution addresses a newly developed semi-analytical model coupling the zone model, virtual point source buoyancy plume theory and mirror theory to predict the gas flow behaviors of leaked hydrogen restricted by a wall or a corner in confined space with an opening. The effects of leaked hydrogen mass flux, opening geometry and the leakage location on interface height, outflow velocity and hydrogen molar fraction in upper layer, were thoroughly investigated at steady stage. A computational fluid dynamics tool, FLACS, was employed to simulate the dispersion process in different leakage scenarios and validate the capability of the derived analytical model. The results show that in all center, wall and corner leakage circumstances, the interface height declines with larger leakage mass flux, whereas the outflow velocity and hydrogen molar fraction change inversely. The interface height, outflow velocity and hydrogen molar fraction are positively, negatively and negatively correlated with the opening dimension, respectively. The opening height plays a more important role in determining the interface height and hydrogen molar fraction but hardly affects the outflow velocity. The interface height keeps unchanged with varying leakage locations when other parameters remain constants. However, according to the mirror theory the outflow velocities in corner and wall leakage conditions are 0.63 and 0.4 times of those in center leakage case. Meanwhile, the hydrogen molar fractions of corner and wall leakages are 1.59 and 2.52 times of the ones in center leakage. All these ratios are validated by the corresponding analytical and numerical predictions. The credibility of the analytical model is verified by the good agreement with the numerical estimations. • A semi-analytical model is developed to estimate the hydrogen gas flow in confined space. • Center, wall and corner leakage scenarios are studied analytically and numerically. • Restricted leakage barely affects interface height but greatly facilitates concentration rise. • Wall and corner leakage outflow velocities are 0.63 and 0.4 times of center leakage. • Wall and corner leakage hydrogen concentrations are 1.59 and 2.52 times of center leakage. [ABSTRACT FROM AUTHOR]

• LME model for semi-batch precipitation in stirred-tanks is presented. • Model considers stirrer type, size and rotational speed. • Model accuracy is validated with experimental comparison setup. • Mixing zone parameterized by pipe-in-pipe geometries. A zone model for the semi-batch precipitation process of sparingly soluble salts in stirred-tank reactors is presented. The low product solubility of these substances leads to high levels of supersaturation during the process. Consequently, nucleation and growth rates are fast and solids formation only takes place in a part of the reactor close to the feed pipe. The presented local mixing environment (LME) model extends an existing model for semi-batch processes, which consists of two zones. In the mixing zone, a steady-state plug-flow reactor (PFR) is used to imitate the local flow environment of the feed. The tank is approximated as a well-mixed storage tank outside the mixing zone. Exchange streams between the two zones are estimated by dimensional analysis considering stirrer type, size and rotational speed. The correctness of the two-zone hypothesis and the accuracy of the LME model is validated by barium sulfate precipitation in an experimental comparison setup using different stirrer types, rotational speeds and feed rates. The PFR is represented in the experiments as a pipe-in-pipe reactor in jet-in-cross-flow (JICF) or coaxial-flow (COAX) arrangement. The experimental results show that the semi-batch precipitation of sparingly soluble salts in stirred-tanks can be successfully simplified by the assumption of a PFR mixing zone. The LME model is simple to implement, scalable and reaches acceptable results in the experimental validation. It is therefore a promising model for future application in process simulation of industrial precipitation processes. [ABSTRACT FROM AUTHOR]

In implementing practical fire Probabilistic Risk Assessment (PRA) for nuclear power plants, a practical fire model is required for more realistic fire scenarios. The fire simulation zone model BRI2-CRIEPI has been continuously improved to allow analysis considering the characteristics of compartment fires under mechanical ventilation conditions. In this study, the specific characteristics of the fire model under mechanical ventilation conditions to estimate inner pressure and flow rate fluctuation were newly applied, such as the relationship between compartment pressure and flow rate of a ventilating fan, i.e., the fan curve, the vitiation effect of the mass loss rate (MLR) due to the depletion of oxygen owing to fire progress, the representative oxygen concentration corresponding to the elevation of a fire source, and a thermal radiation feedback model from the flame and surrounding environment in case of flame impingement beneath the ceiling. The analytical results with the BRI2-CRIEPI were validated by full-scale compartment fire test results performed by the international Organisation for Economic Co-operation and Development (OECD) Nuclear Energy Agency (NEA) project PRISME3 (Propagation d'un incendie pour des scénarios multi-locaux élémentaires in French). Especially, validation result for HGL temperature, which is very important metric in the fire PRA, shows that there is no obvious bias (the model bias factor of 1.03) and no particular systematic trend (the model relative standard deviation of 0.14) in the model prediction. • As part of the PRISME3 project, an experimental study of a large-scale, multi-compartment, multi-source fire was conducted. • The experimental study included three fire scenarios showing complex behavior. • The improvement of the BRI2-CRIEPI is introduced, focusing on the pool fire under mechanically ventilated condition. • The simulated results from BRI2-CRIEPI were validated with the PRISME3 data. • This work is original since the improved BRI2-CRIEPI has not been yet applied to such complex scenarios for validation. [ABSTRACT FROM AUTHOR]

Along with economic development and development of power systems, new, more effective models of the energy market are sought. Traditional zonal models used on the electricity market have proved to be poorly adapted to new circumstances and phenomena occurring in the macroeconomic environment. The main aim of the research was to show the direction (including the nodal model and prosumer behavior) in which the energy market should develop in order to meet the state-of-the-art technical, ecological and social challenges. Therefore, with the new challenges, a new chapter has opened up on very interesting research for the electrical industry. There are new solutions for the development and modernization of models from the point of view of management and econometrics of the energy market, adapted to new challenges related to ecology, technology, and competition. This article presents the zone model with its imperfections and suggestions for its improvement and proposes a nodal model that may in the near future become a new model for the functioning of the electricity market in Europe.

The present paper is dedicated to the modelling of real scale multi-compartment and multi-source fire scenarios and its validation against real scale experiments. The scenarios consist in a one or two fire sources located in a three mechanically ventilated compartments, communicating through vertical openings. The scenarios show complex behaviour and bring new knowledge to the field of compartment fires. It is interesting to assess the ability of the models to predict such complex scenarios. The three scenarios are modelled using the zone model MAGIC, which shows good agreement with the experiments. A second part of the work consists in the use of the Peatross and Beyler correlation to predict the fire behaviour. This correlation, which is intended to account for confinement in a predictive way, is implemented in the zone model MAGIC to achieve this goal. This work is original since this correlation has not been yet applied to such complex scenarios. The important aspects of the correlation, like the reference mass loss rate and the oxygen concentration, were discussed in detail. The correlation is found to give good predictions. • Large-scale multi-compartment and multi-source fire experiments were carried out in the framework of the PRISME 3 project. • The study involved three scenarios showing complex behaviour that has been discussed. • The three scenarios are modelled using the zone model MAGIC, which shows good agreement with the experiments. • Peatross and Beyler correlation is used to predict the fire behaviour by accounting for confinement in a predictive way. • This work is original since this correlation has not been yet applied to such complex scenarios. [ABSTRACT FROM AUTHOR]

An effective optimisation strategy for metal reheating processes is crucial for the economic operation of the furnace while supplying products of a consistent quality. An optimum reheating process may be defined as one which produces heated stock to a desired discharge temperature and temperature uniformity while consuming minimum amount of fuel energy. A strategic framework to solve this multi-objective optimisation problem for a large-scale reheating furnace is presented in this paper. For a given production condition, a model-based multi-objective optimisation strategy using genetic algorithm was adopted to determine an optimal temperature trajectory of the bloom so as to minimise an appropriate cost function. Definition of the cost function has been facilitated by a set of fuzzy rules which is easily adaptable to different trade-offs between the bloom desired discharge temperature, temperature uniformity and specific fuel consumption. A number of scenarios with respect to these trade-offs were evaluated and the results suggested that the developed furnace model was able to provide insight into the dynamic heating behaviour with respect to the multi-objective criteria. Suggest findings that current furnace practice places more emphasis on heated product quality than energy efficiency. [ABSTRACT FROM AUTHOR]

The function and performance of textured polycrystalline thin films are closely related to their microstructures. However, the corresponding growth mechanisms remain unclear, which brings obstacles to the effective engineering of the films' properties. In this work, textured nanocrystalline Indium Oxide (nc-In 2 O 3 ) thin films are prepared and the growth mechanism is explored. Texture morphology within or beyond the prediction of Wulff's theorem and van der Drift's growth mechanism are both observed. The orientation of the textured film changes from (100)-preferred in quasi-equilibrium growth conditions to (111)-preferred in non-equilibrium growth conditions. From a microscopic perspective of adatoms' diffusion, different growth modes for the growth of the textured In 2 O 3 thin films is classified and a quantitative growth zone model is developed. According to the zone model, the morphology and orientation of the films could be successfully designed and controlled by changing growth conditions. [ABSTRACT FROM AUTHOR]

A model for smoke filling in a large room was developed that considers entrainment into the horizontally spreading smoke under the ceiling. This was accomplished by incorporating a simple model for the spreading ceiling jet into the two-layer zone model. Here, the proposed model was validated by focusing on the horizontal smoke spread phase on the basis of the previous experimental data of smoke spread in a large office room. The calculated results were in good agreement with the experimental data. In addition, a case study on the smoke filling in a large room was conducted to clarify the characteristics of the proposed model. As a result, the proposed model can predict the underside of the smoke layer to be lower than the two-layer zone model. [ABSTRACT FROM AUTHOR]

Forecasting building fire growth and smoke dispersion is a challenging task but can provide early warnings to first responders and building occupants and thus significantly benefit active building fire protection. Although existent computer simulation models may provide acceptable estimations of smoke temperature and quantity, most simulations are still not able to achieve real-time forecast of building fire due to high computational requirements, and/or simulation accuracy subject to users' inputs. This paper investigates one of the possibilities of using ensemble Kalman filter (EnKF), a statistical method utilizing the real-time sensor data from thermocouple trees in each room, to estimate the spread of an accidental building fire and further forecast smoke dispersion in real time. A general approach to forecasting building fire and smoke is outlined and demonstrated by a 1:5 scaled compartment fire experiment using a 1.0 kW to 2.8 kW propane burner as fire source. The results indicate that the EnKF method is able to forecast smoke transport in a multi-room building fire using 40 ensemble members and provide noticeable accuracy and lead time. Unlike other methods that directly use measurement data as model inputs, the developed model is able to statistically update model parameters to maintain the forecasting accuracy in real time. The results obtained from the model can be potentially applied to assist mechanical smoke removal, emergency evacuation and firefighting. [ABSTRACT FROM AUTHOR]

Resistance of commercial thermoresistor (TP-68) based on vanadium dioxide film, and tablet pressed from the synthesized VO2 powder is measured on direct and alternating current. For the thermoresistor at measurements on alternating current expansion of a hysteresis loop is revealed. It is established that in conductivity of a semiconductor phase of vanadium dioxide give a contribution both activation, and the hopping mechanism. Temperature dependence of TP-68 resistance in area of phase transition under gases adsorption is studied. The energy zone model is offered for explaining "anomalous" response to the adsorption of donor gases due to inversion of conductivity type in surface layers of vanadium dioxide. [ABSTRACT FROM AUTHOR]

In budding yeast, if the spindle becomes mispositioned, cells prevent exit from mitosis by inhibiting the mitotic exit network (MEN). The MEN is a signaling cascade that localizes to spindle pole bodies (SPBs) and activates the phosphatase Cdc14. There are two competing models that explain MEN regulation by spindle position. In the 'zone model', exit from mitosis occurs when a MEN-bearing SPB enters the bud. The 'cMT-bud neck model' posits that cytoplasmic microtubule (cMT)-bud neck interactions prevent MEN activity. Here we find that 1) eliminating cMT– bud neck interactions does not trigger exit from mitosis and 2) loss of these interactions does not precede Cdc14 activation. Furthermore, using binucleate cells, we show that exit from mitosis occurs when one SPB enters the bud despite the presence of a mispositioned spindle. We conclude that exit from mitosis is triggered by a correctly positioned spindle rather than inhibited by improper spindle position.

Improved thermal efficiency in energy-intensive metal-reheating furnaces has attracted much attention recently in efforts to reduce both fuel consumption, and CO2 emissions. Thermal efficiency of these furnaces has improved in recent years (through the installation of regenerative or recuperative burners), and improved refractory insulation. However, further improvements can still be achieved through setting up reference values for the optimal set-point temperatures of the furnaces. Having a reasonable expression of objective function is of particular importance in such optimisation. This paper presents a function value-based multi-objective optimisation where the objective functions, which address such concerns as discharge temperature, temperature uniformity, and specific fuel consumption, are dependent on each other. Hooke-Jeeves direct search algorithm (HJDSA) was used to minimise the objective functions under a series of production rates. The optimised set-point temperatures were further used to construct an artificial neural network (ANN) of set-point temperature in each control zone. The constructed artificial neural networks have the potential to be incorporated into a more advanced control solution to update the set-point temperatures when the reheating furnace encounters a production rate change. The results suggest that the optimised set-point temperatures can highly improve heating accuracy, which is less than 1 °C from the desired discharge temperature.

The present work deals with a comparative study on various methods for thermal characterization of a fire-induced smoke layer. Models predicting both excess temperature and mean thickness of the smoke layer are focused on. These models are thermodynamically, dynamically or experimentally based. According to the considered models, a preliminary dimensioning is performed for smoke and heat evacuation systems (SHEVS). The obtained results are discussed and confronted with those provided by thermodynamic calculations based on US and European standards. [ABSTRACT FROM AUTHOR]

A model is presented that dynamically predicts the mass loss rate of fuel in a compartment as a function of ventilation, thermal feedback, fuel type and scale. Without a loss of generality, a floor-based fuel is considered. The effect of ventilation is included in the model through the ambient oxygen concentration in the ambient surrounding the fuel at the floor. A mixing model associated with the inlet airflow at the vent is developed to determine this oxygen concentration. An extinction criterion for the flame is based on a critical flame temperature for a diffusion flame associated with the ambient conditions surrounding the flame at the floor. The model is executed in BRI2002, a zone model, capable of computing species and thermal conditions in the upper and lower compartment gas layers. Computations show good agreement with small-scale compartment data for heptane pool fires. The results can accurately portray many regimes of burning including extinction, combustion oscillations, reduction in the flaming area, and quasi-steady burning. [ABSTRACT FROM AUTHOR]

Abstract: Fires in nuclear facilities constitute a significant threat to nuclear safety. A major concern when dealing with safety assessments in nuclear facilities is the confinement of nuclear material by dynamic confinement. Therefore, pressure variations within compartments in case of fire are important to consider. This paper focuses on the capability of a zone model (CFAST) and a field model (ISIS) to predict the interaction between mass loss rate and total relative room pressure or oxygen concentration in case of under-ventilated fire conditions. Results are obtained using as input the mass loss rate measured during the experiment and the mass loss rate measured in free atmosphere. A sensitivity study has also been performed for the field model to analyse the influence on the outputs of soot production, radiation modelling, wall emissivity, turbulence modelling and branch flow resistance. [Copyright &y& Elsevier]

Abstract: Numerical calculations of room fire temperature for t-squared fires were carried out by zone model reflecting the room conditions such as room size, wall construction material, opening size and the fire load density. Based on the numerical results, the correlations for flashover occurrence condition are established, in which the fuel surface area and the temperature factor are used as a room size parameter. A simplified formula for determining the critical heat release rate for flashover is also suggested. The wall construction material has little influence on flashover occurrence. For the boundary of flashover in fuel-controlled fires, as the temperature factor becomes larger, the fuel surface area which causes the flashover occurrence becomes smaller. For ventilation controlled fires, critical fuel surface area per unit internal surface area of room corresponds with temperature factor. As the flashover time is smaller, the critical heat release rate for flashover is increased. By comparing the derived formula with the existing experimental data, it was shown that proposed formula corresponds with lower bound of existing experiments. [Copyright &y& Elsevier]

Abstract: A common way of handling structural fire protection and design is using the so called standard fire as basis for prescriptive design. For this, a wide experimental research with also a large amount of numerical simulations has been carried out in Finland to gather experience of using automatic water extinguishers as a protective method against fire. This research, test methods and the results are presented in this paper. A more modern way of evaluating building''s fire resistance is performance based fire design. This can be carried out in many levels and using different fire models. One way is to use zone models to calculate the temperatures in structures. A case study, now under construction, concerning the use of zone models and OZone software is presented in this paper. [Copyright &y& Elsevier]

Fire risk for building occupants is determined by the time required for safe egress and the time at which untenable conditions develop in building rooms or on the egress routes. In the present study, the CFAST zone model is applied to the simulation of fire development and smoke propagation in multiroom buildings, with the aim of studying the sensitivity of predicted tenability times and quantification of the uncertainties due to variability of the scenario parameters. The building geometries considered are (i) a single room with a door and a window, (ii) three rooms connected by a long corridor, and (iii) two-level configuration with two rooms on the lower floor connected by a vertical vent to a room on the upper floor. Sensitivity indices of the tenability times due to high temperature and smoke obscuration are analyzed. Distribution functions of the tenability times are presented and compared for different building rooms. [ABSTRACT FROM AUTHOR]

We aim to determining the numerical parameter fields for temperature and velocities in order to compare our results with the experimental results of "Turbulent Natural Convection in an Enclosed Tall Cavity" experiments by Betts and Bokhari. Aiming to establish a numerical approach for the free-convective cell we have generated a similar computational domain with the experimental one, applying the motion models (laminar study, viscous stress) and the thermal transfer (free-convection). Our paper leads to a certified algorithm of discretization and heat transfer models that are able to simulate free-convection applications. Actually, the numerical model aims to being validated by the experimental data. We will use for our purpose the FLUENT solver, realized the discretization grid with the GAMBIT routine. As we have realized the mesh in GAMBIT, we have superposed the analysis algorithm in FLUENT and we have realized the comparison using the experimental data. Once we have compared the results, we have stated that the errors range into a 10% maximum error limit. The paper certifies an absolute tool in order to solve free-convection problems. [ABSTRACT FROM AUTHOR]

Abstract: Usually, during a fire inside a tunnel, the average heat release rate (HRR) is estimated according to the type of vehicle. Frequently, the overall HRR is considered, however it is also necessary to know its time evolution to design real time systems, particularly ventilation, which respond to fire events or signals as fast as possible. Nowadays, there is not a well established and generally accepted procedure to know the power liberated at each instant of time inside an operational tunnel. That procedure could help in taking the correct actions to adapt the tunnel ventilation in order to diminish the effects of the fire and the smoke. This work shows a method to calculate the heat release rate using sensors that can be installed inside an operational road tunnel. Besides, the location of the fire could also be calculated accurately and quickly. To achieve the previous purposes, a stationary database that depends on HRR, its location, and the ventilation speed is calculated with CFD programs; the data are compared with temperatures measured by the sensors located inside the tunnel. The program used to generate the database is the simplified model UPMTUNNEL. The predictions of the model are compared with the results of calculations carried out using the general purpose code FLUENT, and with measurements done in a tunnel with a real fire, produced with a fuel tray. [ABSTRACT FROM AUTHOR]

An effective fire and smoke propagation model is important for evaluating building safety, indicating safe rescue paths in emergencies, and determining proper control strategies. In this paper, a new model to simulate smoke propagation and to characterize mixing behavior is developed. In this model, a function considering the mixing behavior between the hot smoke and cool air is introduced to better resolve the temperature and smoke profiles in the vertical direction. Smoothed particle hydrodynamics (SPH) approach is used to obtain the function distribution through reconstructing velocities of marker particles and determining locations of particles in each layer in the zone model. The fundamentals of the model are presented in detail in this paper. A test (a simple building with experimental data and CFD simulation) is used to verify the model, in which experimental data and CFD simulations are compared to predictions from the new model and those from a two-layer model implemented using CFAST (Consolidated Model of Fire and Smoke Transport, developed by NIST). Favorable agreement of the new model results is seen with experiment data or CFD simulations. The new model also provides more accurate prediction of temperature distribution in comparison to the two-layer model. [ABSTRACT FROM AUTHOR]

Abstract: A new simplified model (UPMTUNNEL) for the simulation of accidental fires in road tunnels with longitudinal ventilation is presented. The model follows a mixed approach, and has characteristics typical of both field and zone models. Like field models, the proposed model calculates the main properties at every point in the whole domain. The tunnel is divided in two zones: the plume, located upstream from the point at which the smoke hits the ceiling, and a diffusion zone extending downstream. Each of these two regions is analyzed assuming steady-state conditions. The plume is described by one-dimensional conservation equations for turbulent flows. To deduce the 1D equations, the 3D problem is considered to be parabolic along the center-line of the flame, and self-similar profiles in planes normal to this line are assumed. The diffusion region is studied as an incompressible unidirectional problem, described by the energy conservation equation. 3D models and full-scale experiments have been used in order to validate the results of the UPMTUNNEL model. Two different general-purpose codes are employed: FLUENT and PHOENICS, in which the eddy break-up and k–ε–g turbulent combustion models have been, respectively, implemented. [Copyright &y& Elsevier]

Abstract: A computational model for fire spread in a densely built urban area is developed. The model is distinct from existing models in that it explicitly describes fire spread phenomena with physics-based knowledge achieved in the field of fire safety engineering. In the model, urban fire is interpreted as an ensemble of multiple building fires; that is, the fire spread is simulated by predicting behaviors of individual building fires under the thermal influence of neighboring building fires. Adopted numerical technique for the prediction of individual building fire behavior is based on the one-layer zone model. Governing equations of mass, energy, and chemical species in component rooms are solved simultaneously, for the development of temperature, concentrations of chemical species, and other properties. As for the building-to-building fire spread, three mechanisms are considered as contributing factors of fire spread, i.e., (I) thermal radiation from fire-involved buildings; (II) temperature rise due to wind-blown fire plumes; and (III) firebrand spotting. As for the model verification, fire spread simulations were carried out in a hypothetical urban area, where 2500 buildings of identical configuration were aligned at constant separations. Calculated fire spread rates were then compared with that of the Hamada model, and reasonable agreements were obtained. The model was further verified with the record of a past urban fire, which took place in the city of Sakata in 1976. Although the general features of the fire spread were similar, there were certain discrepancies in the eventual burnt area. The reasons for these discrepancies were discussed and issues for future refinements were stated. [Copyright &y& Elsevier]

An analysis of the sensitivity of the Consolidated Fire and Smoke Transport model to several key fire specification parameters has been performed for this paper. Results of simulations of shipboard fires are compared with data from full-scale experiments. It was found that reasonable estimates of the fire inputs, with the exception of the smoke and carbon monoxide production parameters, could be obtained from literature values. The soot parameter was found to be critical for accurate temperature predictions, especially in the upper layer. [ABSTRACT FROM AUTHOR]

Abstract: Some modifications on Suzuki’s multi-layer zone model (MLZ) have been done to predict temperature and smoke distribution of a tunnel fires, i.e., the radiation heat loss of fire source is taken into account and a four-surface radiation heat transfer model is introduced. Like Suzuki’s model, as a special long and narrow space, the tunnel space is also divided into a number of layers in vertical direction and regions in longitudinal direction. The physical properties like temperature and species (CO,CO2,etc.) are assumed uniform in every zone like two-zone model. However, the different heat transfer model is introduced. The MLZ model prediction is compared with the experiments of USTC and CFD model (FDS). It shows good agreement between the model prediction, experiments and CFD models (FDS). And the MLZ model needs less time than CFD model. [Copyright &y& Elsevier]

Various experimental studies on effect of ventilation on behaviour of fire in compartment are available in literature. Recently, experiments have been conducted to study fire behaviour in compartment with more than one ventilation opening located on opposite walls (Kumar and Naveen, 2007). Two different fuels (benzene and kerosene) are burned in three trays of different size in compartment with single ventilation opening as well as in compartment with two ventilation openings placed on opposite walls (in cross-condition). These results have been used to show how CALTREE (Kumar, 2004), a simple pre-flashover mathematical model to predict temperatures in compartment with single ventilation opening, can be used to predict behaviour of fire in the compartment with cross-ventilation condition. The two methods: equivalent area methods and gas flow methods have been discussed. In the first method there is no need to modify the model developed for the compartment with single ventilation opening. It is found that both the methods give same results in the present study. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports an investigation on the scenarios of the spill plume and the resultant natural filling in a full-scale atrium mock-up due to a retail shop fire. The study includes two aspects, i.e., the full-scale experiment and the numerical simulation. A spill plume model is proposed to predict the characteristic properties of the plume development in the atrium under a retail shop fire. Furthermore, to accurately predict the shop fire in the atrium, an improved zone model is developed combining the transport lag time model and the spill plume model. Besides validating the developed model by experiments, the case is also simulated by the established zone model, i.e., CFAST code, and the computational fluid dynamics model, i.e., FDS code. By both physical and numerical experiments, the process of natural smoke filling and the temperature rise in the atrium are investigated and well understood. It is found that a typical spill plume contains three regimes, i.e., the curved section out of the retail shop door, the line plume in the near field, and the axisymmetric plume in the far field. Predictions from the proposed empirical model for the spill plume and the resultant improved zone model compare favorably with the experiments. The study indicates that the atrium becomes very dangerous due to such shop fire if no smoke control employed. The ability of mechanical exhaust system in the atrium to mitigate the hazard of a retail shop fire is investigated as well. [Copyright &y& Elsevier]

Abstract: Developments in fire engineering and in the understanding of fire influence on humans, together with advances in regulatory base, encourage the use of performance-based methodologies and numerical fire simulation tools in ship design. A numerical method for fire modelling in multiple ship compartments is proposed here, which can be used routinely in the assessment of alternative designs due to its speed and robustness. The method uses an improved treatment of walls between compartments and an efficient algorithm for pressure calculations. The performance of the method is demonstrated on two examples, experimental results for which were available in the literature. [Copyright &y& Elsevier]

Abstract: Provision of make-up air is essential in designing mechanical exhaust system in a compartment. There are always problems in determining the inlet positions for supplying make-up air. In this paper, a zone model for studying the effect of different positions of make-up air supply on the performance of a mechanical exhaust system in an atrium will be developed. Traditional two-layer approach with an upper smoke layer and a lower air layer will be assumed. Three scenarios of extraction with different relative positions of the air inlet are studied. These are scenarios with the smoke layer interface lying above, within, and below the air inlet. Conservation of mass and energy are considered for each scenario to study the smoke filling process. Transient variations of smoke layer temperature and interface height will be predicted under different fire sizes, exhaust rates and make-up air conditions. Full-scale burning tests in an atrium were conducted to justify the predicted results. In addition, results predicted by this zone model will also be compared with those predicted by Computational Fluid Dynamics (CFD) with the software Fire Dynamics Simulator FDS version 3.1; and another zone model CFAST version 5.0.1. It is observed that the predicted results from this new zone model agreed well with experiments and CFD results. However, results predicted by CFAST deviated from experiments for the scenario with the smoke layer interface lying below the air inlet. [Copyright &y& Elsevier]