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

1605091罗，梁颂杰。随着建筑行业能源意识的增强，建筑师和工程师越来越多地使用自然通风作为一种减少能源消耗的方法。虽然自然通风在世界各地的各种文化中已经被使用了数千年，但目前的自然通风设计方法过于简单化，假设流动稳定，因此错误地估计了实际的自然通风率及其相关的能量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强度上固有的不稳定。与机械通风不同，机械通风是由控制良好的风扇驱动的，在目前的方法下，风对通风的影响完全不可预测。这种对知识的缺乏可能会对能源消耗、人类舒适度甚至居住者的整体健康和福祉造成意想不到的后果。为了更好地了解风变化对建筑气流和居住者的影响，本研究项目将针对不同的建筑形式和地点，从通风效率、能量后果和室内空气质量三个方面定量分析风致自然通风气流的影响。本研究项目的这些目标将通过以下几个方面实现：1)研究描述风对建筑变化影响的概率瞬变风效应框架的理想公式，以及研究该度量应作用于的最小时间尺度；2)使用计算流体动力学(CFD)方法和准稳态近似方法，模拟了美国国家海洋和大气管理局(NOAA)在美国毗邻的九个气候区建立的气候带中的风与建筑的相互作用，以选择美国能源部具有代表性的建筑类型；3)调查影响该框架的广泛因素，如通风效率、能源影响、室内空气质量和居住者的生产率和健康。这项研究预计将通过允许工程师针对风能利用潜力进行适当的设计，而不是像大多数现有建筑设计那样将自然通风解决方案视为事后考虑，从而影响建筑设计过程。这一改进将导致更节能的建筑，更高的居住者生产率，以及更低的缺勤率。

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.