Confinement, boundaries and buoyancy in the mixing by fluid flows: towards an understanding of indoor air quality.

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With the increasing urbanisation of society, human health & well-being is ever more affected by the air quality within our cities. We now spend over 90% of our time indoors and so the most chronic exposures can occur inside buildings. Mixing by buoyant fluid flows within buildings plays a dominant role in determining these exposures and the proposed research focuses on the buoyant turbulent plumes that arise in buildings from, the likes of, HVAC systems, window & door openings, radiators, electrical appliances, computers, cooking and the occupants themselves. An extensive campaign of laboratory experiments will examine the physics governing the mixing and transport of heat and tracers by turbulent buoyant plumes within the confining geometry of a room. Current exposure models take no account of the influence on the flow structure of the confinement of a room. The knowledge gained through this research will enable the development of models better suited to predicting indoor exposure levels, thereby enabling better management of exposure. Investigation of these flows also has considerably broader relevance and future application to examine include, for example, the mixing and dilution of flows within our urban environments, the mixing of fluids in the food, beverage & pharmaceutical industries, and the pollutant and nutrient transport in the Earth's oceans. This work will investigate factors which affect the mixing by fluid flows typical of the flows within building, specifically by: 1) De-coupling the effects of confinement from those of the no-slip condition which are typically simultaneously introduced into a fluid flow by the presence of a boundary - this is of fundamental scientific interest; 2) Varying the extent of the confinement imposed on the flow by the introduction of a jointed wall so that the degree of confinement can be continuously varied. The jointed wall can mimic the confinement of a corner formed by the meeting of two walls within a room. The angle of this corner wall can then be systematically varied to replicate the confinement imposed when, for example, people or computer equipment are placed, for example, near a corner within a room, next to a plane wall, or indeed near an obtuse 'external' corner. The new understanding will enable better modelling of the mixing produced by heat sources, including people, radiators and computers, within rooms - providing a practical output of real application and value to society.