A. Grandison

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.

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.

The development of a CFD based simulator for water mist suppression systems: the development of the fire submodel

The FIRE Detection and Suppression Simulation (FIREDASS) project was concerned with the development of water misting systems as a possible replacement for halon based fire suppression systems currently used in aircraft cargo holds and ship engine rooms. As part of this program of work, a computational model was developed to assist engineers optimize the design of water mist suppression systems. The model is based on Computational Fluid Dynamics (CFD) and comprised of the following components: fire model; mist model; two-phase radiation model; suppression model; detector/activation model. In this paper the FIREDASS software package is described and the theory behind the fire and radiation sub-models is detailed. The fire model uses prescribed release rates for heat and gaseous combustion products to represent the fire load. Typical release rates have been determined through experimentation. The radiation model is a six-flux model coupled to the gas (and mist) phase. As part of the FIREDASS project, a detailed series of fire experiments were conducted in order to validate the fire model. Model predictions are compared with data from these experiments and good agreement is found.

A fast, streaming simd extensions 2, logistic squashing function

Schraudolph proposed an excellent exponential approximation providing increased performance particularly suited to the logistic squashing function used within many neural networking applications. This note applies Intels streaming SIMD Extensions 2 (SSE2), where SIMD is single instruction multiple data, of the Pentium IV class processor to Schraudolphs technique, further increasing the performance of the logistic squashing function. It was found that the calculation of the new 32-bit SSE2 logistic squashing function described here was up to 38 times faster than the conventional exponential function and up to 16 times faster than a Schraudolph-style 32-bit method on an Intel Pentium D 3.6 GHz CPU.

Methods and Tools for Risk-Based Approach to Fire Safety in Ship Design

Abstract The FIREPROOF project aims to develop a risk-based performance assessment framework for fire safety in passenger ship design. Building on previous work on probabilistic damaged stability, this framework requires developments in modelling, simulation and analysis in several areas to allow the probabilistic representation of ship performance. To support the FIREPROOF framework, an outline Ship Product Model (SPM) was developed, demonstrating the modelling and information storage methods required of future CAD tools to be compatible with the risk based approach. This supported the use of simulation based analysis on a model representative of early stage ship design.