Paul Jowitt

The influence of longitudinal ventilation systems on fires in tunnels

Abstract Many tunnels are equipped with longitudinal ventilation systems to control smoke in the event of a fire. However, the influence of such ventilation on fire development and fire spread has rarely been considered. This paper presents the results of a study investigating the influence of forced longitudinal ventilation on car fires, pool fires and heavy goods vehicle fires in tunnels. A Bayesian probabilistic approach is used to refine estimates, made by a panel of experts, with data from experimental fire tests in tunnels. Results are presented and the implications are discussed. The influence of longitudinal ventilation on heavy goods vehicle fires is predicted to be much larger than the experts’ estimates, causing a fire to grow ten times larger than if natural ventilation was used. The effect of ventilation on a pool fire in a tunnel depends on the size of the pool; the heat release rate of small pool fires may be reduced by forced ventilation, whereas it may be enlarged for large pool fires. The size of a car fire is not expected to be greatly affected by forced ventilation at low ventilation velocities.

Variation of heat release rate with forced longitudinal ventilation for vehicle fires in tunnels

Many tunnels are equipped with longitudinal ventilation systems to control smoke in the event of a fire. However, the influence of such ventilation on fire development and fire spread has rarely been considered. This paper presents the results of a study using a Bayesian methodology to estimate the effect of forced longitudinal ventilation on heat release rate (HRR) for fires in tunnels. The behaviour of car and heavy goods vehicle (HGV) fires with a range of forced ventilation velocities is investigated. Results are presented and the implications are discussed. It has been found that forced ventilation has a great enhancing effect on the HRR of HGV fires, but has little effect on the HRR of car fires.

Some new insights on informational entropy for water distribution networks

Several researchers have studied the use of informational entropy as a surrogate measure for the reliability of water distribution networks. The hypothesis is that the numerical value of network entropy in some way reflects the reliability of water distribution networks, and this appears to be supported by the analysis of some example water distribution networks. However, the precise relationship between the entropy value and some measures of reliability has not been formally established. The primary objective in this paper is to present an alternative methodology to calculate the informational entropy of water distribution networks. This methodology is termed as the Path Entropy Method (PEM), which provides some insights into the entropy of branching-tree networks and maximum-entropy flows of single-source networks. In addition, a quick method of computing the maximum-entropy value of single-source networks is presented and termed as the Simplified Path Entropy Method (SPEM).

SWARD: decision support processes for the UK water industry

In industrialised countries water service providers (WSPs) must provide an appropriate level of service with an acceptable performance at an acceptable cost to customers. In the UK a move towards sustainable development is now also a major goal for WSPs. However, the imposition of institutional systems and regulatory targets still encourage the adoption of less sustainable technologies or solutions by the water industry. It is within this context, that the Sustainable Water industry Asset Resource Decisions (SWARD) project has developed a set of decision support processes that allow WSPs to assess the relative sustainability of water/wastewater system asset development decisions. A Guidebook has been produced that takes the WSP and its stakeholders through the processes essential to incorporating sustainability in asset investment decision‐making. Several case studies that demonstrate the SWARD principles in application are included within the Guidebook, the experience of which is described in this paper.

Some observations on energy loss and network entropy in water distribution networks

The design of water distribution networks has been extensively studied with the aid of computers, and the focus has shifted from merely satisfying the hydraulic requirements to fulfilling the need for reliability. One of the interesting research areas recently is the use of informational entropy as a surrogate measure for reliability. The actual meaning of the informational entropy for water distribution network has not been fully elucidated, and it was hypothesed that reliability is in some way proportional to the numerical value of network entropy. The purpose of this paper is to explore the relationship between energy loss and network entropy. The investigation approach used is to take a simple looped network and individually vary the pipe diameters from zero to infinity, and calculate the corresponding network entropy and energy loss for the water distribution network. The results revealed many interesting observations in the variation of network entropy with pipe resistance coefficient K i , and the revelation of local maximum and minimum points.

Making more sustainable decisions for asset investment in the water industry - sustainable water industry asset resource decisions - the SWARD project

Effective Integrated Water Management (IWM) is an aspiration for all those engaged in water service provision, and is a key component of the World Water Vision. Part of this includes the sustainability of water systems and their interaction with other urban systems. In the urban drainage field, there are many examples of attempts to establish effective integrated systems. A major problem, however, is the elusive nature of the concept of sustainability and how to translate what is known in terms of sustainability principles and objectives into action within the IWM perspective. Case studies are presented that illustrate how urban drainage problems can be approached in a way that takes due account of sustainability considerations. These studies utilise a new Guidebook that presents multi-criteria decision support systems to assist Water Service Providers (WSPs) to assess the relative sustainability of water/wastewater system asset development decisions. The Guidebook was developed as part of a UK government and industry funded multi-partner project over the past 4 years. An essential feature of the Guidebook is its transparency, as it is intended to be accessible to all stakeholders affected by a proposed development.

Decision mapping : understanding decision making processes

The task of arriving at an engineering decision typically involves extensive and complex analyses, the evaluation of alternatives, and the resolution of conflicts between stakeholders. Research into institutional frameworks, decision making, and decision support tools have guided improvements in the quality of decisions. However, existing organisational structures and decision frameworks must be acknowledged and addressed if the desired improvements are to be realised. A mapping technique is proposed that allows the existing decision-making processes and information flows to be identified and analysed. The result is a mechanism to understand the context and processes of the decision task, and ultimately to aid in the introduction of new decision protocols and decision support systems.

A BAYESIAN ESTIMATION OF THE EFFECT OF FORCED VENTILATION ON A POOL FIRE IN A TUNNEL

Abstract A Bayesian methodology is used to estimate the effect of longitudinal forced ventilation on heat release rate (HRR) for fires in tunnels. The behaviour of three different sizes of pool fires with a range of forced ventilation velocities is investigated. Results are presented and the implications are discussed. It has been found that for some fires the ventilation would be expected to reduce the HRR and for some fires to increase it. Overall, expert opinions have been found to differ significantly.

Path entropy method for multiple-source water distribution networks

Over the past decade, one of the key research areas for water distribution networks has been the quantification of network reliability. An interesting approach in this research topic is the use of informational entropy as a surrogate measure for the reliability of water distribution network. Research on water distribution network entropy has progressed to the stage where practical applications are possible, but the actual meaning of the network entropy has never been fully elucidated. Recently, an alternative approach to calculate network entropy was proposed, which was termed the path entropy method (PEM). This alternative method was shown to be useful for the case of single-source water distribution networks. The purpose of this article is to explore the use of the PEM on multiple-source networks. A two-source and two-demand water distribution network is analysed to gain insight into the differences between single-source and multiple-source networks in terms of maximum-entropy flow distribution. This leads to the formal proof of the principle governing maximum-entropy flow ratios in multiple-source water distribution networks.

Reservoir yield assessment in a changing Scottish environment

The application of a variety of reservoir yield estimation methods is described against the background of a review of yield in Scotland. The study is timely, both in the context of the possible effects of climate change, the institutional re-organisation of the water industry world-wide--but originating largely from the UK-and the emerging issues of sustainability and the shift from supply to demand side management. To set the paper in context, the study was undertaken just prior to the transfer of responsibility for water supply from regional councils to new water authorities in 1996, and following the quinquennial Scottish Office Environment Departments survey of water resources in 1994. A comparative review of assessment methods was undertaken in order to recommend a flexible and consistent approach for single sources, but with a view to extending this to conjunctive schemes. A case study of Loch Bradan showed that the derivation of the inflow record and definition of the catchment boundary are at least as important as the yield assessment method itself.