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

随着社会城市化程度的提高，城市空气质量对人类健康和福祉的影响越来越大。我们现在有超过90%的时间是在室内度过的，所以最长期的接触可能发生在建筑物内。建筑物内浮力流体流动的混合在决定这些暴露方面起着主导作用，拟议的研究重点是建筑物中产生的浮力湍流羽流，如暖通空调系统，门窗开口，散热器，电器，电脑，烹饪和居住者本身。一项广泛的实验室实验活动将检验在一个房间的封闭几何结构中，由湍流浮力羽流控制热量和示踪剂的混合和传输的物理学。目前的暴露模型没有考虑室内封闭对流动结构的影响。通过这项研究获得的知识将有助于开发更适合于预测室内暴露水平的模型，从而能够更好地管理暴露。对这些流动的调查也具有相当广泛的相关性，未来的应用包括，例如，我们城市环境中流动的混合和稀释，食品、饮料和制药工业中流体的混合，以及地球海洋中污染物和营养物质的运输。这项工作将研究影响建筑物内典型流动的流体混合的因素，具体方法是：1)将约束效应与无滑移条件的效应分离开来，无滑移条件通常是由边界的存在同时引入流体流动的——这是基本的科学兴趣；2)通过引入节理墙来改变对流动施加的约束程度，使约束程度可以连续变化。接缝墙可以模仿房间内两面墙相遇形成的角落的限制。然后，这个角墙的角度可以系统地变化，以复制施加的限制，例如，人或计算机设备被放置，例如，在房间的角落附近，在平面墙旁边，或者在一个钝角的“外部”角附近。新的认识将使更好地模拟室内热源（包括人、散热器和计算机）产生的混合——为社会提供真正应用和价值的实际产出。

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.