Warren Spring Laboratory

Abstract This paper describes the work of an INCOSE UK Advisory Board working group set up to define the set of Core Competencies for Systems Engineering. The development of complex products (systems) demands a broad range of competencies from its system engineering resource. An agreed set of core competences would allow individuals and enterprises to establish an effective, transferable portfolio of skills, which can be deployed in systems projects. Such a set of core competences will also provide a framework for education/training and assessment. The working group recognized that in addition to core competencies, Supporting Techniques, Basic Skills and Behaviours and Domain Knowledge are important. This paper offers a set of core competencies for Systems Engineering and guidance on how to use them.

The first report1 to appear on this incident dated July 1996 was that of the Sea Empress Environmental Evaluation Committee (SEEEC). This gave an introductory account of events which may be summarised as follows.

In the preceding chapters, we have seen how growing understanding of the problems of spillage response in terms of the nature of the oil-water system, and of the interaction between individual oil properties and post-spillage processes, has led to the development of a range of response techniques and equipment for use at sea and on shorelines. We have also seen how the strengths and weaknesses of these resource options can be understood in terms of the nature of the oil-water system, of sea state and of shoreline type; and how this understanding in turn provides a basis for selection of techniques and equipment for optimal effectiveness for any given spill situation, oil type and extent of emulsification.

Abstract The value of knowing the gas residence times in large municipal incinerators and the serious error imposed by the traditional use of gas volume flow rate based average residence time with regard to these incinerators are recognized. There is increasing public awareness and concern over emissions from municipal solid waste incinerators. Modelling studies of particle trajectories using computational fluid dynamics shows the utility of simulation for the determination of residence time distribution in incinerators. These studies indicate that residence time distributions contain valuable information, important to the understanding and evaluation of mixing processes in the incinerator overfire region. A number of design modifications and changes in operational conditions (which have a major influence on the mean gas residence times and overall performance of two large municipal incinerator plants (35 MW and 65 MW) are proposed. Specifically, the effect of high speed jets and different internal baffle configurations have been investigated using mathematical modelling, in an attempt to obtain optimum combustion conditions. This would increase the mean gas residence times, minimize the emission of pollutants and improve the temperature profile throughout the system. The utility of having detailed RTD information for the incinerator overfire region is demonstrated by estimating the residence times using numerical simulation of tracer injection into the 3‐dimensional reacting flow field of two typical municipal incinerator configurations. The modelling results not only underscore the critical role played by jets in achieving desirable states of mixing in the overfire region but also point to the significance of the geometry effects.This modelling work has yielded important results, all of which clearly could not be experimentally verified at the industrial scale due to practical and cost limitations. Nevertheless, the results guide specific modifications to the design and operation and this new approach will be of considerable use to the incinerator design community.

Dispersion, although one of the most important processes in determining the fate of oil in the sea, is still poorly understood.This poster presents the first successful field measurements of oil droplet size distribution below oil slicks, a major step in understanding the dispersion process at sea and in designing a dispersant efficiency test that relates to conditions at sea.If simplified, the process of dispersion can be divided in two stages: the formation of oil droplets in the water column from the surface slick, and advection of these droplets by near-surface turbulence down into the water column to prevent resurfacing.By Stoke's law, smaller oil droplets rise more slowly than large droplets.Thus, conditions that result in increased near-surface turbulence and generate a greater number of smaller oil droplets produce faster dispersion rates.The measurement of oil droplet size distributions at sea is, therefore, central to understanding this dispersion process.It also provides a means of quantifying the effects of different environmental conditions and chemical surfactants on surface slicks, and hence a way of predicting dispersion rates.Currently available dispersant efficiency tests, such as the Warren Spring Laboratory (WSL), Mackay-Nadeau-Steelman (MNS), and Institut Français de Pétrole (IFP) tests, produce different efficiency values for the same combinations of oil and dispersant.These different efficiency values have been shown to be related in part to the different amounts of energy each test imparts to the system and hence the different sizes of oil droplet sizes produced. 1These tests have not been designed to relate to oil droplet sizes observed at sea.

Abstract The aerodynamic behavior of aggregates consisting of uniform polystyrene latex (PSL) spheres and unaggregated cuboidal Natrojarosite particles in a TSI aerodynamic particle sizer (Model APS33B) has been studied. In initial tests, monodisperse PSL micro-spheres ranging from 0.3 to 7 μm in geometric diameter were generated from aqueous suspensions using a Lovelace nebulizer. APS33B responses for these uniform-sized particles showed multiple peaks. The major (primary) peak, which resulted from the smallest particle, corresponded to the unaggregated single spheres (singlets); the second, third, and fourth peaks were identified as doublets, triangular triplets, and tetrahedral quadruplets, respectively. Both doublets and triplets moved with their long axes in perpendicular (maximum drag) orientation to the flow direction in the APS33B. In contrast, the tetrahedral particles were isometric and had the same dynamic shape factor (drag resistance) for all three primary orientations. The particle Reynolds numbers (Re p) for these particles were calculated and ranged from 0.2 to 30 in the sensing volume of the APS33B detector (i.e., ultra-Stokesian conditions). Ultra-Stokesian drag forces for all three types of aggregates were, therefore, estimated and expressed as a function of an empirical factor (1 + aRe b p) to the Stokesian drag force. The ultra-Stokesian drag of a Natrojarosite particle was measured in the range 20 Re p < 50 and could be described with a similar expression. This approach facilitates the study of the dynamic behavior of nonspherical particles and yields new information about the characteristics of drag forces in the ultra-Stokesian regime