Dispersed flows of droplets and particles abound in nature; from clouds, mist and fogs to the long-range transport of fine dust released in desert storms or in volcanic eruptions. Such flows control the weather and influence the climate. They play key roles in many industrial energy processes from spray drying, pneumatic and slurry transport, fluidized beds, to coal gasification and mixing and combustion processes. They can have a profound effect on our health and quality of life, from the spread of communicable diseases to the inhalation of very fine air-borne particulates. Modelling and computing all of the above process accurately and efficiently is therefore important in our control of the environment, improving our health, and in the design and improvement of industrial processes.This proposal is about developing and applying a novel approach to modelling and computing these processes. The approach is called the probability density function (pdf) approach and is analogous to the kinetic theory of gases in that, central to the approach, is a master equation (analogous to the Maxwell-Boltzmann equation) from which can be derived the basic continuum conservation equations and associated constitutive relations for the treatment of the particulate phase as a fluid (e.g.expressions for the viscous shear stress of the fluid in terms of the rate of straining of the fluid). Whilst two-fluid model equations (for the treatment of both the carrier and particle phases as fluids) are the most efficient way of computing the transport of both phases, and ideal for implementation within the standard framework of a CFD code, it has long been recognised that they have severe limitations because the wall-boundary conditions necessary for solution of the equations for the dispersed phase are incompatible with the natural wall boundary conditions. This is because particle wall interactions are concerned with changes in the particle velocity at the wall which are not a feature of two-fluid model equations. Whilst several attempts have been made to incorporate particle-wall interactions into the standard boundary conditions of two-fluid models, the boundary conditions so contrived are artificial and depend upon some a priori knowledge of the particle velocity distribution at the wall. The significant feature of the pdf approach is that it deals with the particle velocity distribution as well as that of its position so that the boundary conditions for the solution of the pdf equation are compatible with those of the natural boundary conditions. Whilst this proposal will use pdf methods to develop and solve the continuum equations of the particulate phase, the most challenging aspect is the application of pdf methods to particle-wall interactions and near wall behaviour where because of the imposed boundary conditions and the steep changes in wall turbulence, continuum equations are inapplicable. Such restrictions do not apply to the pdf approach. The strategy for calculating particle flows using a pdf approach, will be to divide the flow into near and far wall regions. In the near wall region the pdf equations will be used exclusively to obtain wall functions which incorporate the natural boundary conditions and the near wall behaviour. These wall functions will then be used to solve for the far wall behaviour where the continuum equations will be derived from the pdf method. The work proposed is both innovating and challenging from both the modelling and computational points of view: the application of the pdf method explicitly to solve for the near wall behaviour and particle wall interactions is radical and entirely new; matching the near wall solution (wall function) with the far wall flow solution will require an entirely new numerical approach, whilst the solutions of the far wall continuum equations will in themselves require the use of non-standard techniques.

The overall research project is about the design of complex microstructures (and processes for their manufacture) to achieve salt reduction in foods. The aim is, not simply to reduce salt, or replace it by man-made materials but to carefully establish salt delivery profiles that present no taste compromise to the consumer. Thereby, a minimum amount of salt is delivered to the consumer to help the food industry work towards government guidelines of reducing the salt intake by offering the consumer a choice of salt reduced processed foods. Salt in processed foods is closely linked to flavour, indeed, salt is often added as a flavour enhancer. Hence, the delivery of not salt release profiles as well as the delivery of acceptable, overall flavour delivery profiles are subjects for this research. The experimental approach will consist of in-vivo measuring of the dynamic release and perception of volatile and non-volatile compounds in model fluids and foods as well as the resulting saliva flow rate. The experimental work will be followed by modelling (supported by the consortium leader Unilever) to deliver appropriate targets to feed into the design rules for the food microstructures to be developed by another consortium partner (University of Birmingham). Model fluids will initially consist of simple aqueous mixtures of sodium chloride ('salt') and potassium chloride. Potassium chloride, as opposed to sodium chloride, does not carry any health risks to the consumer since it is the sodium ion that is linked to problems such as coronary heart desease. Indeed, a lack of potassium in the general diet has been reported. It enhances the perceived perception of saltiness, however, it is also perceived as bitter when delivered in too high concentrations. Appropriate mixtures and delivery profiles need to be carefully evaluated. As a next step, flavours will be added to ensure that the delivered flavour profiles will still be acceptable to the consumer. The flavours will be commercial savoury flavours such as chicken, beef, mushroom, and garlic since the overall project is likely to target a sauce or dressing as the demonstrator food product in its final delivery stage. Real foods are more complex in their physical-chemical properties than aqueous solutions of salt, hence, model fluids or model foods studied will be chosen with increasing degreees of complexity in their microstructure, material composition and rheology. Our scientific ambition is to push forward the understanding between the sensory science parameters related to this project, i.e., perceived saltiness and flavour, and food composition/material behaviour. In a systematic way, we will change the rheological behaviour of the model fluids including shear rheology and extensional rheology. As a next step, a second food phase, which can be a solid phase or a liquid phase, will be introduced. A second liquid phase can be oil-based, or aqueous based and studied in an emulsion system, or phase-separated biopolymer mixtures respectively. Solid phases of interest include gel particles and starch granules, both of which are often present in foods. The latter have recently been demonstrated to influence salt perception (Prof. John Mitchell, University of Nottingham). Our group will also be responible for testing the sensory properties of the initial microstructures, the model foods, and finally, a real food product. The sensory properties will then be determeind to ensure that the design rules developed for the model systems can be applied to real foods.

Storm water runoff typically contains and transports a wide range of pollutants, resulting in negative environmental effects with potential threats to ecosystems and health. Hundreds of runoff treatment ponds intended to moderate these impacts are likely to be delivering sub-optimal (and perhaps actually below legally required) levels of improvement in water quality due to poor understanding of flow patterns and the effects of vegetation. This proposal will generate a unique dataset to describe the influence of different types and configurations of vegetation on the pond's fundamental flow - and treatment - characteristics. We will also deliver a validated set of vegetative resistance and mixing parameters that are essential if 3D numerical modelling tools are to be used with confidence. These tools will ensure that future pond designs meet all their water quality and ecosystem services objectives for current legislation and the increasingly stringent EU regulatory framework anticipated over the next decade. Stormwater ponds take run-off from urban areas, highways and agricultural land, providing detention and attenuation of peak storm discharges and improving water quality. Stormwater ponds are able to provide protection to downstream drainage components and receiving waters by holding or treating run-off at or near the source and provide additional nature conservation and amenity benefits. Within the Highways Agency Asset Inventory System alone there are currently over 800 stormwater ponds. Pond performance (pollutant treatment efficiency) is directly related to hydraulic residence time, a function of the internal flow field, which in turn is controlled by the pond geometry and the distribution and type of vegetation present. The prediction of water quality improvements within drainage features is gaining importance with stormwater professionals. However, performance prediction is complex since water quality processes are functions of the pond hydraulic residence time. Current evaluations employ the nominal retention time which assumes plug flow through the pond, as the design consideration. It is accepted that the nominal retention time (pond volume/discharge) provides a poor estimate of the actual mean (or median) residence time, with overestimates of treatment times of 100% or more not being uncommon. However, it is still in use, even 'the norm'. In wastewater treatment wetlands, treatment is good since a high degree of engineering is adopted in creating an efficient, often linear, shape with uniform, dense, vegetation. In contrast, stormwater ponds must fit into existing water courses or urban environments. Together with the additional requirements for biodiversity and ecological function, this leads to pond layouts that may be less than ideal from a hydraulic perspective. Vegetation can have either a positive or negative role in water quality treatment within stormwater ponds. It provides the appropriate environment for the support of biofilms and the colonisation by algae, enhancing treatment, yet variable spatial distribution influences the spread of the hydraulic residence time. This proposal seeks to better understand and quantify the physical, vegetation-driven, flow mechanisms occurring within a stormwater pond and to develop a robust physically based modelling tool. The research proposed here will deliver improved understanding of the effects of vegetation (type: emergent, floating and submerged; physical characteristics: porosity and spatial distribution) on flow patterns and residence time distributions within stormwater ponds. The validated numerical modelling approach will permit the assessment of short circuiting, a measure of poor performance, and provide estimates for vegetation contact times, sediment deposition regions and rates. This will provide a tool for predicting the treatment efficiency of vegetated stormwater ponds.

If the carbon dioxide produced when coal is burnt to make electricity can be collected in a concentrated form then it can be compressed into a dense liquid and squeezed into the pores between rock grains a kilometre or more underground. By putting the carbon dioxide (CO2 ) in places where the porous rocks are sealed by layer of non-porous rocks we can be very confident that most of it will stay there for tens of thousands of years, so it won't increase the risk of dangerous climate change. But current coal power stations don't release the CO2 in a concentrated form; it is mixed with about five times its volume of nitrogen and oxygen, from the air used to burn the coal. One way to avoid this is to burn the coal in pure oxygen instead of air. We know this can theoretically be made to work, but if pure oxygen - or really a 'synthetic air' made up of oxygen and recycled combustion products instead of nitrogen - is used to burn coal then many things would be different from using air. This project will develop the scientific understanding that power plant builders and operators need to predict and cope with these differences.To help develop a better scientific understanding of oxyfuel combustion we will undertake experiments in a 150 kW laboratory burner. This is small (1% of the size!) compared to real power plant burners, but it will use the same oxygen/flue gas mixture. Computer models will be developed to analyse how the coal burns in the laboratory scale burner. These models can then be applied to full scale burners. Using the power available from modern computer systems it is now possible to track the behaviour of all of the swirling gases and particles in a flame ands see how they move and react over very small intervals of time. It's possible - but we are still learning how to do it properly. To help us do this we are taking high speed (1000 frames per second) video recordings of our laboratory oxyfuel flames to see how they really flow and flicker and using the bright and precise beams from laser to help track how particles move and to tell us what sort of gas mixtures are present.We are also reproducing just some of the things that happen in flame in special test equipment so that we have simpler things to measure. These measurements then go into the computer models. How coal particles first catch alight and then how they char and burn are particularly important. We are also interested how the ash in the coal will behave. It can cause problems coating the walls of air-fired power plants, but after a lot of experience we know how to avoid that. Some of those lessons are probably going to have to be re-learned for oxyfuel combustion and the experts who help to sort out air combustion are now starting to do that on our project. We are also looking at how oxyfuel combustion products might attack the steels used in boilers; new materials might be needed, especially in hot or dusty locations.Finally, we need to have trained scientists and engineers to help design and build these new types of power plants. Our project will help to train a number of these, and also build up the experience in the academic community that can be used to advise industry when they come to build and operate new oxyfuel plants. We will also have developed some of the new measurement techniques that can be used to help tune the first plants to give the best possible performance.But no project can do it all. So we are working closely with other groups in the UK and overseas - the IEA Greenhouse Gas Programme coordinates an excellent network that we belong too. And as we learn more we also expect to come up with more questions that need to be answered plus some good ideas for ways to do that.

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.