J. Ewer

Simulating one of the CIB W14 round robin test cases using the SMARTFIRE fire field model

Numerical predictions produced by the SMARTFIRE fire field model are compared with experimental data. The predictions consist of gas temperatures at several locations within the compartment over a 60 min period. The test fire, produced by a burning wood crib attained a maximum heat release rate of approximately 11 MW. The fire is intended to represent a non-spreading fire (i.e. single fuel source) in a moderately sized ventilated room. The experimental data formed part of the CIB Round Robin test series. Two simulations are produced, one involving a relatively coarse mesh and the other with a finer mesh. While the SMARTFIRE simulations made use of a simple volumetric heat release rate model, both simulations were found capable of reproducing the overall qualitative results. Both simulations tended to over-predict the measured temperatures. However, the finer mesh simulation was better able to reproduce the qualitative features of the experimental data. The maximum recorded experimental temperature (1214°C after 39 min) was over-predicted in the fine mesh simulation by 12%.

Coupled Fire/Evacuation Analysis of the Station Nightclub Fire

In this paper, coupled fire and evacuation simulation tools are used to simulate the Station Nightclub fire. This study differs from the analysis conducted by NIST in three key areas; (1) an enhanced flame spread model and (2) a toxicity generation model are used, (3) the evacuation is coupled to the fire simulation. Predicted early burning locations in the full-scale fire simulation are in line with photographic evidence and the predicted onset of flashover is similar to that produced by NIST. However, it is suggested that both predictions of the flashover time are approximately 15 sec earlier than actually occurred. Three evacuation scenarios are then considered, two of which are coupled with the fire simulation. The coupled fire and evacuation simulation suggests that 180 fatalities result from a building population of 460. With a 15 sec delay in the fire timeline, the evacuation simulation produces 84 fatalities which are in good agreement with actual number of fatalities. An important observation resulting from this work is that traditional fire engineering ASET/RSET calculations which do not couple the fire and evacuation simulations have the potential to be considerably over optimistic in terms of the level of safety achieved by building designs.

Smartfire: an Intelligent Cfd Based Fire Model:

This paper describes a project aimed at making Computational Fluid Dynamics (CFD) based fire simulation accessible to members of the fire safety engineering community. Over the past few years, the practise of CFD based fire simulation has begun the transition from the confines of the research laboratory to the desk of the fire safety engineer. To a certain extent, this move has been driven by the demands of performance based building codes. However, while CFD modelling has many benefits over other forms of fire simulation, it requires a great deal of expertise on the user’s part to obtain reasonable simulation results. The project described in this paper, SMARTFIRE, aims to relieve some of this dependence on expertise so that users are less concerned with the details of CFD analysis and can concentrate on results. This aim is achieved by the use of an expert system component as part of the software suite which takes some of the expertise burden away from the user. SMARTFIRE also makes use of the latest developments in CFD technology in order to make the CFD analysis more efficient. This paper describes design considerations of the SMARTFIRE software, emphasising its open architecture, CFD engine and knowledge based systems.

Evacuation analysis of 1000+ seat Blended Wing Body aircraft configurations: Computer Simulations and Full-Scale Evacuation Experiment

Blended Wing Body (BWB) aircraft with around 1000 passengers and crew are being proposed by aircraft manufacturers. This type of aircraft configuration is radically different from conventional tube type passenger aircraft and so it is essential to explore issues related to both fire and evacuation for these configurations. Due to both the large size and the unusual nature of the cabin layouts, computer simulation provides the ideal method to explore these issues. In this paper we describe the application of both fire and evacuation simulation to BWB cabin configurations. The validity of the computer evacaution simulations is also explored through full-scale evacuation experiments.

Case study: an incremental approach to re-engineering a legacy FORTRAN computational fluid dynamics code in C++

This article describes a practical approach to the manual re-engineering of numerical software systems. The strategy has been applied to re-develop a medium sized FORTRAN-77 Computational Fluid Dynamics (CFD) code into C++. The motivation for software reverse-engineering is described, as are the special problems which influence the re-use of a legacy numerical code. The aim of this case study was to extract the implicit logical structure from the legacy code to form the basis of a C++ version using an imposed object-oriented design. An important secondary consideration was for the preservation of tried and tested numerical algorithms without excessive degradation of run-time performance. To this end an incremental re-engineering strategy was adopted that consisted of nine main stages, with extensive regression testing between each stage. The stages used in this development are described in this paper, with examples to illustrate the techniques employed and the problems encountered. This paper concludes with an appraisal of the development strategy used and a discussion of the central problems that have been addressed in this case study.

CFD Fire Simulation of the Swissair Flight 111 in-Flight Fire - Part 1: Prediction of the Pre-Fire Air Flow Within the Cockpit and Surrounding Areas

The SMARTFIRE computational fluid dynamics (CFD) software was used to predict the ‘possible’ behaviour of airflow as well as the spread of fire and smoke within a Swissair configured McDonnell Douglas MD-11 commercial transport aircraft. This work was undertaken by the Fire Safety Engineering Group (FSEG) of the University of Greenwich as part of Transportation Safety Board (TSB) of Canada, Fire & Explosion Group’s investigation into the in-flight fire occurrence onboard Swissair Flight 111 (SR111): TSB Report Number A98H0003. The main aims of the CFD analysis were to develop a better understanding of the possible effects, or lack thereof, of numerous variables relating to the in-flight fire. This assisted investigators in assessing possible fire dynamics for cause and origin determination. In Part 1, the numerical analyses to pre-fire airflow patterns within the cockpit and its vicinity are presented. The pre-fire simulations serve two ends. One is to provide insight into the flow patterns within the cockpit and its vicinity and further supportive numerical evidence for the airflow flight test observations. The other is to provide plausible initial flow conditions for fire simulations. In this paper, some flow patterns at a number of primary locations within the cockpit and its vicinity are highlighted and the predicted flow patterns are compared with the findings from the airflow flight tests. The predicted patterns are found to be in good qualitative agreement with the experimental test findings.

Case-based retrieval of 3-dimensional shapes for the design of metal castings

This paper describes research into retrieval based on 3-dimensional shapes for use in the metal casting industry. The purpose of the system is to advise a casting engineer on the design aspects of a new casting by reference to similar castings which have been prototyped and tested in the past. The key aspects of the system are the orientation of the shape within the mould, the positions of feeders and chills, and particular advice concerning special problems and solutions, and possible redesign. The main focus of this research is the effectiveness of similarity measures based on 3-dimensional shapes. The approach adopted here is to construct similarity measures based on a graphical representation deriving from a shape decomposition used extensively by experienced casting design engineers. The paper explains the graphical representation and discusses similarity measures based on it. Performance measures for the CBR system are given, and the results for trials of the system are presented. The competence of the current case-base is discussed, with reference to a representation of cases as points in an n-dimensional feature space, and its principal components visualization. A refinement of the case base is performed as a result of the competence analysis and the performance of the case-base before and after refinement is compared.

Fire and evacuation analysis in BWB aircraft configurations: Computer simulations and large-scale evacuation experiment

How long would it take to evacuate a blended wing body (BWB) aircraft with around 1,000 passengers and crew? How long would it take an external post-crash fire to develop non-survivable conditions within the cabin of a BWB aircraft? Is it possible for all the passengers to safely evacuate from a BWB cabin subjected to a post-crash fire? These questions are explored in this paper through computer simulation. As part of project NACRE, the airEXODUS evacuation model was used to explore evacuation issues associated with BWB aircraft and to investigate fire issues, the CFD fire simulation software SMARTFIRE was used. The fire and evacuation simulations were then coupled to investigate how the evacuation would proceed under the conditions produced by a post-crash fire. In conjunction with this work, a large-scale evacuation experiment was conducted in February 2008 to verify evacuation model predictions. This paper presents some of the results produced from this analysis.

The Development of Parallel Implementation for a CFD Based Fire Model Utilising Conventional Office Based PCs

Parallel processing techniques have been used in the past to provide high performance computing resources for activities such as fire-field modelling. This has traditionally been achieved using specialized hardware and software, the expense of which would be difficult to justify for many fire engineering practices. In this article we demonstrate how typical office-based PCs attached to a Local Area Network has the potential to offer the benefits of parallel processing with minimal costs associated with the purchase of additional hardware or software. It was found that good speedups could be achieved on homogeneous networks of PCs, for example a problem composed of ~100,000 cells would run 9.3 times faster on a network of 12 800MHz PCs than on a single 800MHz PC. It was also found that a network of eight 3.2GHz Pentium 4 PCs would run 7.04 times faster than a single 3.2GHz Pentium computer. A dynamic load balancing scheme was also devised to allow the effective use of the software on heterogeneous PC networks. This scheme also ensured that the impact between the parallel processing task and other computer users on the network was minimized.

Development of a hybrid field/zone fire model

A novel hybrid field/zone fire model, coupling the SMARTFIRE CFD fire model to both the CFAST zone model and a custom zone model is presented. The intention of the hybrid model is to reduce the computational overheads incurred in using fire field models to simulate large geometries such as large buildings or large passenger ships, while maintaining the accuracy of the fire field model. In using the hybrid model, only the most important parts of the geometry are fully modeled using the field model. Other less important parts of the geometry are modeled using the zone model. From the field model’s perspective, the zone model is used to represent parts of the geometry as an accurate boundary condition. By using this approach, many computational cells are replaced by a simple zone model, saving computational costs. Two tests cases demonstrating the technique are presented. It is shown that the hybrid approach is capable of producing reasonably accurate predictions of fire development while substantially reducing computational costs. It is shown that by removing some 56% of the CFD solution domain, the hybrid case can achieve a saving of 48% in the run time.