P.G. Holborn

Nonlinear dynamics of flashover in compartment fires

Flashover is a phenomenon whereby a room fire undergoes a rapid increase in size and intensity. Such a transition is suggestive of a nonlinear process. We therefore seek to apply modern geometrical and computational techniques of nonlinear dynamics to a simplified model of fire growth to investigate flashover and other instabilities occuring in compartment fires. We present here a simplified model of fire growth in a compartment and conduct a preliminary analysis of the dynamics exhibited, in terms of both transient simulations and quasi-steady evolution manifolds, for variations in controlling parameters.

Experimental and theoretical models of flashover

A comparison between experimental data and both the qualitative and quantitative nonlinear behavior predicted by a fire growth model is made for a model compartment (0·4 m cube). The predictions are in relatively good agreement with the data, and are consistent with the expected nonlinear behaviour and in particular the occurrence of flashover jumps.

Dynamic modelling of building fires

This paper examines the dynamical behavior of fire growth within a building or more simply a compartment. Simplified equations are derived to study the development of a fire. The transient fire growth is modelled using concepts of nonlinear dynamical systems theory, and the effect of ventilation is considered. Emphasis is placed on qualitative behavior with a view to understanding the phenomena involved in fire growth, with specific attention focused on highly dangerous flashover conditions.

Fundamental study of generation of interfacial temperatures with metal surfaces and coatings under conditions of sliding friction and mechanical impact

Abstract The measurement of surface temperatures generated by sliding friction is discussed and experiments are carried out using dynamic thermocouples to determine surface temperatures arising from sliding friction and mechanical impact. Experimental results over a very wide range of loading and velocity conditions show an appreciable degree of similarity with calculated values using the equations given in part one of this study. Impacts with a 7·3 kg projectile with nickel and nickel coated test heads onto an angled steel anvil, have shown that very high transient surface temperatures can be reached. At velocities above 5 m s−1, surface temperatures in excess of 1000°C are obtained within a contact duration of less than 2 ms. The lower temperatures recorded in the case of impacts involving nickel plated steel test heads correspond to the temperature difference across the thickness of the coating rather than to the difference in surface temperature and the cold junction.

Fundamental study of generation of interfacial temperatures with metal surfaces and coatings under conditions of sliding friction and mechanical impact Part 1 - Thermal analysis and theoretical evaluation of surface temperature

Abstract A study has been carried out to evaluate the surface temperatures reached on sliding metallic surfaces over a wide range of conditions. This is of interest for a number of reasons, including determining the conditions of mechanical sliding friction which might be associated with failure or loss of adhesion of a coating intended to prevent galling or seizure and establishing the likelihood of igniting any pyrophoric substances present on the surface. In Part 1 of the study, the uncertainties involved in determining the surface temperature are considered and a thermal analysis performed to illustrate how variations in the properties of the contacting surfaces, together with the loading and sliding conditions influence the surface temperature. A numerical analysis of the heat transferred into the bulk of the metal indicates that in many cases the generated temperature increase will significantly decay over a comparable depth to that of an engineering metal coating.

The effect of variation of ventilation and other control parameters in a compartment fire model

The dynamical behaviour of fire growth within a compartment is examined. A simplified dimensionless model is derived in order to study the development of a fire and the effect of parameter variations on the stationary states investigated. Attention is focused on the occurrence of flashover jumps and the influence of ventilation on the models behaviour.

Experimental comparison with a compartment fire model

A comparison between the predictions from a previously derived non-dimensional fire growth model and experimental data obtained from a series of fire experiments in a scale (0.4 m cube) compartment is made. Both the qualitative and quantitative types of theoretical behaviour appear to be in reasonable agreement with those found experimentally.