Variability of wind effects on natural ventilation and pollutant transport in buildings

[1605091]卢亮，钟杰。随着建筑行业节能意识的增强，建筑师和工程师越来越多地使用自然通风作为减少能源消耗的手段。虽然自然通风已经在世界各地的各种文化中使用了数千年，但目前设计自然通风的现代方法过于简单，并且假设气流稳定，因此错误地估计了实际的自然通风率及其相关的能源和室内空气质量影响。这种困难背后的关键原因是风在方向和大小上的固有不稳定性。与机械通风不同的是，机械通风是由风扇驱动的，并且控制得很好，在目前的方法下，风对通风的影响是完全不可预测的。这种知识的缺乏可能会导致能源消耗，人类舒适度，甚至居住者的整体健康和福祉方面的意想不到的后果。为了更好地了解风变率对建筑气流和居住者的影响，本研究项目将定量分析不同建筑形式和地点的风驱动自然通风流在通风效果、能源后果和室内空气质量方面的影响。研究项目的目标将通过：1)研究描述风对建筑物的可变影响的概率瞬态风效应框架的理想公式，以及研究该度量应该在什么最小时间尺度上运行；2)利用计算流体动力学（CFD）方法和准稳态近似，模拟美国九个国家海洋和大气管理局（NOAA）建立的气候带的风-建筑相互作用，选择美国能源部的代表性建筑类型；3)调查框架影响的广泛因素，如通风效果、能源影响、室内空气质量和居住者的生产力和健康。预计这项研究将影响建筑设计过程，使工程师能够正确地设计风力利用潜力，而不是像大多数现有建筑设计那样，将自然通风解决方案作为事后考虑。这一改进将带来更节能的建筑，更高的居住者生产力和更低的缺勤率。

1605091 Lo, Liang Chung J.With expanding energy consciousness in the building sector, architects and engineers have been increasingly using natural ventilation as a means to reduce energy expenditures. While natural ventilation has been used for thousands of years in various culture worldwide, the current modern method of designing for natural ventilation is simplistic and assumes steady flow, thus misestimating actual natural ventilation rates and their associated energy and indoor air quality impacts. The key reason behind such difficulty is the inherent unsteadiness of the wind in both its direction and magnitude. Unlike mechanical ventilation, which is driven by fans with well-tuned control, the wind's effect on ventilation is wholly unpredictable given the current approach. Such lack of knowledge may result in unintended consequences in energy consumption, human comfort, and even the overall health and wellbeing of the occupants. To better understand the consequences on building airflow and occupants of wind variability, this research project will analyze quantitatively, for different building forms and locales, the impacts of wind-driven natural ventilation flow in terms of ventilation effectiveness, energy consequences, and indoor air quality.These goals of the research project will be accomplished by: 1) Researching the ideal formulation of a probabilistic transient wind effect framework that describes wind's variable impacts on buildings, as well as researching what minimum time scale that metric should operate on; 2) Simulating wind-building interactions in the nine National Oceanic and Atmospheric Administration (NOAA) established climate zones in the contiguous United States for a selections of building types from Department of Energy's representative building stock in the U.S., using both computational fluid dynamics (CFD) methods and quasi-steady state approximations; 3) Investigating a broad spectrum of factors of the impact of the framework, such as ventilation effectiveness, energy impacts, and indoor air quality and occupant productivity and health. The research is anticipated to impact the building design process by allowing engineers to properly design for the wind harnessing potential, rather than considering natural ventilation solutions as an afterthought as in most existing building designs. This improvement would result in more energy efficient buildings, higher occupant productivity, and lower absenteeism rates.