Fluid dynamics of Urban Tall-building clUsters for Resilient built Environments (FUTURE)

世界正在经历快速的城市化，到2050年，预计将有很大比例的人口（约70%）生活在城市环境中。城市移民的主要解决方案是建造高层建筑（TBs），这允许高密度的人口（和商业活动）居住在我们城市的中心。然而，近年来人们越来越关注密集城市环境中的公共健康和福祉。例如，众所周知，城市热岛效应（城市地区通常比周围的农村地区热几度）可能导致热浪期间的死亡率。正如伦敦规划b[3]所承认的那样，为了加剧这些问题，“一些气候变化是不可避免的……”，这可能会增加极端天气事件的频率和严重程度，以及随之而来的城市健康风险。当前的COVID-19危机也凸显了预测病原体扩散和城市地区高效室内外通风的重要性[b]。因此，通过确保空气质量、污染物排放的运输和城市内的小气候（如风、温度、污染物浓度和人为热）不会因城市发展规划不当和缺乏战略方向而达到不可持续的水平，从而建立健康和可持续的城市环境符合公众利益。最近的举措正在促进城市环境卫生和可持续性的研究（例如，英格兰公共卫生部的“健康-波利斯”项目）。尽管高层建筑的扩散可能会加剧上述一些问题，但目前的天气和空气质量模型并不能考虑结核及其对城市社区内风和温度场的长期影响。这主要与所研究现象的主要小尺度有关，与这些模型通常在最先进的计算机能力、资源可用性和周转时间的限制下实现的空间分辨率（即数百米的数量级）形成对比。另一方面，学术界使用的计算流体力学方法的空间分辨率要高得多，即适合解决这些城市塔楼的存在。然而，这些研究模拟通常缺乏充分捕捉真实环境流动（例如大气条件，热交换）所需的许多物理，并且通常在更小的域上运行。因此，对更真实的详细模拟和更好的大规模操作模型参数化有双重需求，前者为后者的发展提供了信息。为了克服这些限制，该项目将采用风洞试验、实地观测、高保真计算机辅助分析和理论模型的协同作用。这将使我们能够(i)了解风场和温度场对描述结核病的几何参数的依赖，无论是孤立的还是集群的，以及（ii）开发参数化和开源模型，这些模型可以随时为政策制定者和监管机构提供，以帮助他们建设更具弹性的城市环境。其目的是开发公开可用的快速周转模型，描述tb对具有不同复杂程度的用户的兴趣数量的影响。这将包括针对地方当局的“经验法则”设计原则，以及适合在大型数值天气预报和空气质量软件中实施的技术模型参数化，以服务于专业和业务建模社区。参考文献[1]《世界城市化展望》修订版（2018）。DESA,联合国。[2]Vardoulakis et al.（2016）。环境卫生15，S30. bbb伦敦计划（2017）。大伦敦当局ECDC技术报告（2020）。欧洲疾病预防控制中心。

The world is witnessing rapid urbanisation, where a large percentage of its population is expected to live within urban environments - circa 70% - by 2050 [1]. The main solution to urban immigration has been to construct tall buildings (TBs), which allow for a high-density population (and commercial activities) to reside in the hearts of our cities. However, recent years have witnessed increasing concerns regarding public health and wellbeing in dense urban environments. For instance, it is known that the urban heat island effect, where urban areas are typically some degrees hotter than the surrounding rural areas, can contribute to death rates during heatwaves [2]. To exacerbate these issues, as recognised by the London Plan [3], ''some climate change is inevitable..." and this is likely to increase the frequency and severity of extreme weather events, and the consequent urban health risks. The current COVID-19 crisis has also highlighted the importance of predicting pathogen dispersion and of efficient indoor/outdoor ventilation in urban areas [4]. It is, therefore, in the public interest to build healthy and sustainable urban environments by ensuring that air quality, transport of pollutant emissions, and the microclimate within cities (e.g. winds, temperatures, pollutant concentrations, and anthropogenic heat) do not reach unsustainable levels from poor urban development planning and lack of strategic directions. Recent initiatives are now promoting research on urban environmental health and sustainability (e.g. Public Health England's project Healthy-Polis). Despite the likely effects of the proliferation of tall structures in exacerbating some of the problems discussed above, current weather and air quality models do not cater for TBs and their long-lasting effects on the winds and temperature fields within urban neighbourhoods. This mostly relates to the dominant small scales of the phenomena under examination, in contrast to the spatial resolution that these models typically achieve (i.e. of the order of hundreds of metres) within the constraints of state-of-the-art computer power, resource availability, and turnaround time. On the other hand, the spatial resolution of computational fluid dynamics methods used in academia is much higher i.e. appropriate to resolve the presence of these urban towers. However, these research simulations often lack much of the physics needed to adequately capture real environmental flows (e.g. atmospheric conditions, heat exchange), and are generally run over much smaller domains. Hence, there is a dual need for more realistic detailed simulations and better parametrisations for larger-scale operational models, with the former informing development of the latter.To overcome these limitations, this project will employ a synergy of wind-tunnel tests, field observations, high-fidelity computer-aided analysis, and theoretical models. This will allow us to (i) understand the dependence of wind and temperature fields on the geometric parameters describing TBs both in isolation and as a cluster, and (ii) to develop parametrisations and open-source models that can be readily available to policymakers and regulators to assist them in building more resilient urban environments. The aim is to develop publicly available fast turnaround models that describe the effect of TBs on the quantities of interest for users with different levels of sophistication. This will include "rule-of-thumb" design principles aimed at local authorities and technical model parametrisations suitable for implementation in larger numerical weather prediction and air quality software to serve the professional and operational modelling community. References[1] Revision of World Urbanization Prospect (2018). DESA, UN.[2] Vardoulakis et al. (2016). Environmental Health 15, S30.[3] The London Plan (2017). Greater London Authority.[4] ECDC Tech. Report (2020). European Centre for Disease Prevention and Control.