The airEXODUS evacuation model and its application to aircraft safety

Computer based mathematical models describing the aircraft evacuation process have a vital role to play in the design and development of safer aircraft, the implementation of safer and more rigorous certification criteria, in cabin crew training and post-mortem accident investigation. As the risk of personal injury and the costs involved in performing full-scale certification trials are high, the development and use of these evacuation modelling tools are essential. Furthermore, evacuation models provide insight into the evacuation process that is impossible to derive from a single certification trial. The airEXODUS evacuation model has been under development since 1989 with support from the UK CAA and the aviation industry. In addition to describing the capabilities of the airEXODUS evacuation model, this paper describes the findings of a recent CAA project aimed at investigating model accuracy in predicting past certification trials. Furthermore, airEXODUS is used to examine issues related to the Blended Wing Body (BWB) and Very Large Transport Aircraft (VLTA). These radical new aircraft concepts pose considerable challenges to designers, operators and certification authorities. BWB concepts involving one or two decks with possibly four or more aisles offer even greater challenges. Can the largest exits currently available cope with passenger flow arising from four or five aisles? Do we need to consider new concepts in exit design? Should the main aisle be made wider to accommodate more passengers? In this paper we discuss various issues evacuation related issues associated VLTA and BWB aircraft and demonstrate how computer based evacuation models can be used to investigage these issues through examination of aisle/exit configurations for BWB cabin layouts.

Birth-death processes with disaster and instantaneous resurrection

A new structure with the special property that instantaneous resurrection and mass disaster are imposed on an ordinary birth-death process is considered. Under the condition that the underlying birth-death process is exit or bilateral, we are able to give easily checked existence criteria for such Markov processes. A very simple uniqueness criterion is also established. All honest processes are explicitly constructed. Ergodicity properties for these processes are investigated. Surprisingly, it can be proved that all the honest processes are not only recurrent but also ergodic without imposing any extra conditions. Equilibrium distributions are then established. Symmetry and reversibility of such processes are also investigated. Several examples are provided to illustrate our results.

Computational fire engineering - do we have what we need?

This presentation will attempt to address the issue of whether the engineering design community has the knowledge, data and tool sets required to undertake advanced evacuation analysis. In discussing this issue I want to draw on examples not only from the building industry but more widely from where ever people come into contact with an environment fashioned by man. Prescriptive design regulations the world over suggest that if we follow a particular set of essentially configurational regulations concerning travel distances, number of exits, exit widths, etc it should be possible to evacuate a structure within a pre-defined acceptable amount of time. In the U.K. for public buildings this turns out to be 2.5 minutes, internationally in the aviation industry this is 90 seconds, in the UK rail industry this is 90 seconds and the international standard adopted by the maritime industry is 60 minutes. The difficulties and short comings of this approach are well known and so I will not repeat them here, save to say that this approach is usually littered with “magic numbers” that do not stand up to scrutiny. As we are focusing on human behaviour issues, it is also worth noting that more generally, the approach fails to take into account how people actually behave, preferring to adopt an engineer’s view of what people should do in order to make their design work. Examples of the failure of this approach are legion and include the; Manchester Boeing 737 fire, Kings Cross underground station fire, Piper Alpha oil platform explosion, Ladbroke Grove Rail crash and fire, Mont Blanc tunnel fire, Scandinavian Star ferry fire and the Station Nightclub fire.

Simulation of ship evacuation and passenger circulation

This paper describes work carried out in the FIRE EXIT research project. FIRE EXIT aims to develop an Evacuation Simulator, capable of addressing issues of mustering, ship motions, fire and abandonment. In achieving these aims, FIRE EXIT took as its starting point the state-of-the-art in ship evacuation simulation (the maritimeEXODUS software), fire simulation (the SMARTFIRE software) and large-scale experimental facilities (the SHEBA facility). It then significantly enhanced these capabilities. A number of new technologies have been developed in achieving these objectives. The innovations include directly linking CFD fire simulation with evacuation and abandonment software and automatic data transfer from concept design software allowing rapid generation of ship simulation models. Software usability was augmented by a module for interpretation of evacuation software output. Enhancements to a ship evacuation testing rig have resulted in a unique facility, capable of providing passenger movement data for realistic evacuation scenarios and large scale tests have provided meaningful data for the evacuation simulation.

The effect of thermal cycle profiles on solder joint damage

The relationship between the damage caused at different thermal cycles is very important. The whole of accelerated thermal cycle testing is based on the premise that damage at one cycle is representative of damage at a different cycle. In this paper, the relative damage caused by six thermal cycle profiles are predicted using Finite Element (FE) modelling and the results validated against experiments. Both creep strain and strain energy density were used as damage indicators and creep strain was found to correlate better with experiment. The validated FE model is then used to investigate the effect of altering each of the thermal profile parameters (ramp and swell times, hot and cold temperatures). The components used for testing are surface mount resistors - 1206, 0805 and 0603. The solders investigated are eutectic SnAgCu and eutectic SnAg.

A systematic comparison of buildingEXODUS predictions with experimental data from the Stapelfeldt trials and the Milburn House evacuation

In this paper, the buildingEXODUS evacuation model is described and discussed and attempts at qualitative and quantitative model validation are presented. The data sets used for validation are the Stapelfeldt and Milburn House evacuation data. As part of the validation exercise, the sensitivity of the building-EXODUS predictions to a range of variables is examined, including occupant drive, occupant location, exit flow capacity, exit size, occupant response times and geometry definition. An important consideration that has been highlighted by this work is that any validation exercise must be scrutinised to identify both the results generated and the considerations and assumptions on which they are based. During the course of the validation exercise, both data sets were found to be less than ideal for the purpose of validating complex evacuation. However, the buildingEXODUS evacuation model was found to be able to produce reasonable qualitative and quantitative agreement with the experimental data.

The use of computer simulation for aircraft evacuation certification: a report from the VERRES project

In this paper a methodology for the application of computer simulation to the evacuation certification of aircraft is suggested. The methodology suggested here involves the use of computer simulation, historic certification data, component testing and full-scale certification trials. The proposed methodology sets out a protocol for how computer simulation should be undertaken in a certification environment and draws on experience from both the marine and building industries. Along with the suggested protocol, a phased introduction of computer models to certification is suggested. Given the sceptical nature of the aviation community regarding any certification methodology change in general, this would involve as a first step the use of computer simulation in conjunction with full-scale testing. The computer model would be used to reproduce a probability distribution of likely aircraft performance under current certification conditions and in addition, several other more challenging scenarios could be developed. The combination of full-scale trial, computer simulation (and if necessary component testing) would provide better insight into the actual performance capabilities of the aircraft by generating a performance probability distribution or performance envelope rather than a single datum. Once further confidence in the technique is established, the second step would only involve computer simulation and component testing. This would only be contemplated after sufficient experience and confidence in the use of computer models have been developed. The third step in the adoption of computer simulation for certification would involve the introduction of several scenarios based on for example exit availability instructed by accident analysis. The final step would be the introduction of more realistic accident scenarios into the certification process. This would require the continued development of aircraft evacuation modelling technology to include additional behavioural features common in real accident scenarios.

An analysis of passenger performance on stairs and upper deck slides during evacuation trials: a report from the VERRES project

This paper reports on research work undertaken for the European Commission funded study GMA2/2000/32039 Very Large Transport Aircraft (VLTA) Emergency Requirements Research Evacuation Study (VERRES). A particular focus of VERRES was on evacuation issues and several large-scale evacuation trials were conducted in the CRANFIELD simulator. This paper addresses part of the research undertaken for Work Package 3 by the University of Greenwich with a focus on the analysis of the data concerning passenger use of stairs and passenger exit hesitation time analysis for upper deck slides.

Proposed methodology for the use of computer simulation to enhance aircraft evacuation certification

In this paper a methodology for the application of computer simulation to evacuation certification of aircraft is suggested. This involves the use of computer simulation, historic certification data, component testing, and full-scale certification trials. The methodology sets out a framework for how computer simulation should be undertaken in a certification environment and draws on experience from both the marine and building industries. In addition, a phased introduction of computer models to certification is suggested. This involves as a first step the use of computer simulation in conjunction with full-scale testing. The combination of full-scale trial, computer simulation (and if necessary component testing) provides better insight into aircraft evacuation performance capabilities by generating a performance probability distribution rather than a single datum. Once further confidence in the technique is established the requirement for the full-scale demonstration could be dropped. The second step in the adoption of computer simulation for certification involves the introduction of several scenarios based on, for example, exit availability, instructed by accident analysis. The final step would be the introduction of more realistic accident scenarios. This would require the continued development of aircraft evacuation modeling technology to include additional behavioral features common in real accident scenarios.

On Reynolds number and scaling effects in microchannel flows

This paper presents a numerical study of the Reynolds number and scaling effects in microchannel flows. The configuration includes a rectangular, high-aspect ratio microchannel with heat sinks, similar to an experimental setup. Water at ambient temperature is used as a coolant fluid and the source of heating is introduced via electronic cartridges in the solids. Two channel heights, measuring 0.3 mm and 1 mm are considered at first. The Reynolds number varies in a range of 500-2200, based on the hydraulic diameter. Simulations are focused on the Reynolds number and channel height effects on the Nusselt number. It is found that the Reynolds number has noticeable influences on the local Nusselt number distributions, which are in agreement with other studies. The numerical predictions of the dimensionless temperature of the fluid agree fairly well with experimental measurements; however the dimensionless temperature of the solid does exhibit a significant discrepancy near the channel exit, similar to those reported by other researchers. The present study demonstrates that there is a significant scaling effect at small channel height, typically 0.3 mm, in agreement with experimental observations. This scaling effect has been confirmed by three additional simulations being carried out at channel heights of 0.24 mm, 0.14 mm and 0.1 mm, respectively. A correlation between the channel height and the normalized Nusselt number is thus proposed, which agrees well with results presented.

A computational study of the characteristics of aircraft post-crash fires

Full-scale furnished cabin fires have been studied experimentally for the purpose of characterising the post-crash cabin fire environment by the US Federal Aviation Administration for many years. In this paper the Computational Fluid Dynamics fire field model SMARTFIRE is used to simulate one of these fires conducted in the C-133 test facility in order to provide further validation of the computational approach and the SMARTFIRE software. The experiment involves exposing the interior cabin materials to an external fuel fire, opening only one exit at the far end of the cabin (the same side as the rupture) for ventilation, and noting the subsequent spread of the external fire to the cabin interior and the onset of flashover at approximately 210 seconds. Through this analysis, the software is shown to be in good agreement with the experimental data, producing reasonable agreement with the fire dynamics prior to flashover and producing a reasonable prediction of the flashover time i.e. 225 seconds. The paper then proceeds to utilize the model to examine the impact on flashover time of the extent of cabin furnishings and cabin ventilation provided by available exits

Predicting the likely impact of aircraft post crash fire on aircraft evacuation using fire and evacuation simulation

The SMARTFIRE Computational Fluid Dynamics (CFD) fire field model has successfully reproduced the observed characteristics including measured temperatures, species concentrations and time to flashover for a post-crash fire experiment conducted by the FAA within their C-133 cabin test facility. In this test only one exit was open in order to provide ventilation for the developing cabin fire. In real post-crash fires, many exits are likely to be open as passangers attempt to evacuate. In this paper, the likely impacts on evacuation of a post-crash fire in which various exiting combinations are available are investigated. The fire scenario, investigated using the SMARTFIRE software, is based on the C-133 experiment but with a fully furnished cabin and with four different exit availability options. The fire data is imported into the airEXODUS evacuation simulation software and the resulting evacuations examined. The combined fire and evacuation analysis reveals that even though the aircraft configuration is predicted to comfortably satisfy the evacuation certification requirement, when fire is included, a number of casualties result, even from the certification compliant exit configuration.

Role of bonding time and temperature on the physical properties of coupled anisotropic conductive–nonconductive adhesive film for flip chip on glass technology

Using thermosetting epoxy based conductive adhesive films for the flip chip interconnect possess a great deal of attractions to the electronics manufacturing industries due to the ever increasing demands for miniaturized electronic products. Adhesive manufacturers have taken many attempts over the last decade to produce a number of types of adhesives and the coupled anisotropic conductive-nonconductive adhesive film is one of them. The successful formation of the flip chip interconnection using this particular type of adhesive depends on, among factors, how the physical properties of the adhesive changes during the bonding process. Experimental measurements of the temperature in the adhesive have revealed that the temperature becomes very close to the required maximum bonding temperature within the first 1s of the bonding time. The higher the bonding temperature the faster the ramp up of temperature is. A dynamic mechanical analysis (DMA) has been carried out to investigate the nature of the changes of the physical properties of the coupled anisotropic conductive-nonconductive adhesive film for a range of bonding parameters. Adhesive samples that are pre-cured at 170, 190 and 210°C for 3, 5 and 10s have been analyzed using a DMA instrument. The results have revealed that the glass transition temperature of this type of adhesive increases with the increase in the bonding time for the bonding temperatures that have been used in this work. For the curing time of 3 and 5s, the maximum glass transition temperature increases with the increase in the bonding temperature, but for the curing time of 10s the maximum glass transition temperature has been observed in the sample which is cured at 190°C. Based on these results it has been concluded that the optimal bonding temperature and time for this kind of adhesive are 190°C and 10s, respectively.

Simulating the interaction of occupants with signage systems

This paper describes the introduction of chained signage systems into evacuation simulation models. Signage systems are widely used in buildings to provide information for wayfinding, thereby providing exiting information during emergencies and assisting in navigation during normal circulation of pedestrians. Recently a system was developed to introduce simple signs into egress models. The system, known as Visibility Catchment Area or VCA, allowed similated agents to interact with signs which point directly to an exit and signs which are located directly above the exit. However, this approach was not able to represent the more general situation of a sign netwokr within an arbitrarily complex building. In this paper we extend the method to include chained signage systems which provides simulated agents that are unfamiliar with the structure a means by which to navigate to an emergency exit. The model includes the associated navigation behaviours exhibited by occupants that rely on a signage system for navigation including: Searching behaviours, Backtracking behaviours, Lost behaviours and Communication behaviours. The new features are demonstrated through a series of demonstration cases and are shown to produce plausible results.

Extended model of pedestrian escalator behaviour based on data collected within a Chinese underground station

This paper presents data relating to pedestrian escalator behaviour collected in an underground station in Shanghai, China. While data was not collected under emergency or simulated emergency conditions, it is argued that the data collected under rush-hour conditions - where commuters are under time pressures to get to work on time - may be used to approximate emergency evacuation conditions - where commuters are also under time pressures to exit the building as quickly as possible. Data pertaining to escalator/stair choice, proportion of walkers to riders, walker speeds and side usage are presented. The collected data is used to refine the buildingEXODUS escalator model allowing the agents to select whether to use an escalator or neighbouring parallel stair based on congestion conditiions at the base of the stair/escalator and expected travel times. The new model, together with the collected data, is used to simulate a series of hypothetical evacuation scenarios to demonstrate the impact of escalators on evacuation performance.