Atmospheric Boundary Layer Studies

通常是湍流的大气边界层（ABL），其典型深度约为1公里，是我们大多数人生活、工作和娱乐的地方。我的研究小组在过去研究了许多与ABL流动相关的问题，包括使用模型和实地研究的复杂地形（例如山丘和粗糙度变化）上的流动。尽管许多研究小组对ABL进行了长期的研究，但在我们对一些重要实际问题（如雾和陆地表面状况）的理解和预测方面仍有重大改进的机会。未来5年的一个目标将是研究边界层内的雾，并仔细探索它可能发展和后来消散的条件。这包括热、水（蒸汽和液滴）、辐射（长波和短波）和云物理过程的湍流传递。另一个重要的应用ABL研究领域是冬季道路状况的研究。除了湍流传输外，加上地表和次地表条件，这些在很大程度上取决于太阳和长波辐射通量，而太阳和长波辐射通量受到低空云存在的强烈影响。例如，与改进的ABL模型相结合，将允许扩展17年前在加拿大环境部开发的非常广泛使用的METRo预测模型。我们的主要方法将继续是湍流边界层建模。有两种基于计算机的方法，大涡模拟（LES）和求解具有某种形式湍流闭合的Reynolds平均Navier-Stokes （RANS）方程。我的研究小组在过去的不同项目中都使用过这两种方法。我们将在这里关注RANS建模，但在某些情况下LES具有优势，例如调查雾“斑块”和车辆尾流情况。我还计划详细探讨RANS模型中的闭包问题。一般来说，RANS模型将湍流动能（TKE）作为变量之一，并将“主长度尺度”l或TKE耗散率作为另一个变量。这些在大多数情况下看起来令人满意，并且在一定程度上依赖于这样一个概念，即能量在大尺度上被投入湍流谱，然后在很小的尺度（< 1mm）上通过谱“级联”消散并转化为热量。在某些情况下，例如风力涡轮机尾迹，或车辆后面的尾迹，在中等规模（叶片或车辆宽度）存在额外的TKE输入。我们将研究如何有效地表现这一过程。主要的研究目标将是扩大ABL研究的范围，我的小组有专业知识，并包括辐射效应。其中包括对道路和空中安全有重大影响的应用，如雾。我们将有兴趣通过行业或政府合作来开发这些潜力，但依赖于NSERC发现基金支持基础研究，以启动和支持更多的应用研究。

The, usually turbulent, atmospheric boundary layer (ABL) with a typical depth of about 1 km, is where most of us live, work and play. My research group have worked on many issues related to ABL flows in the past, including the flow over complex terrain (hills and roughness changes for example) using both models and field studies. Despite a long record of ABL studies by many research groups there are still opportunities for significant improvements in our understanding and forecasting of some important practical issues, such as fog and land surface conditions.One objective over the next 5 years will be to study fog within the boundary layer and to carefully explore the conditions under which it can develop and later dissipate. These involve a mix of turbulent transfer of heat, water (vapor and droplets), radiation (long and short wave) and cloud physics processes.Another important applied ABL research area is a study of winter road conditions. In addition to turbulent transfers, plus surface and sub-surface conditions these can depend to a considerable extent on solar and long wave radiation fluxes, strongly influenced by the presence of low level cloud. Coupling with an improved ABL model would, for example, allow an extension of the very widely used METRo forecast model, developed 17 years ago at Environment Canada.Our main approach will continue to be turbulent boundary-layer modeling. There are two computer-based approaches, Large Eddy Simulation (LES) and solving the Reynolds Averaged Navier-Stokes (RANS) equations with some form of turbulence closure. My research group has used both in the past for different projects. We will focus here on RANS modeling, but there are situations where LES has advantages, for example to investigate fog "patchiness", and vehicle wake situations.I also plan to explore a detailed closure issue in RANS models. In general RANS models will include turbulence kinetic energy (TKE) as one of the variables and either a "master length scale", l, or a TKE dissipation rate, , as another. These appear satisfactory in most cases and rely to some extent on the concept that energy is put into the turbulence spectrum at large scales and then "cascades" through the spectrum to be dissipated and converted to heat at very small scales (< 1mm). In some cases such as wind turbine wakes, or wakes behind vehicles, there is an additional input of TKE at an intermediate scale (blade or vehicle width). We will investigate ways to effectively represent this process.The main research goal will be to expand the range of ABL studies that my group have an expertise in and to include radiative effects. These include applications, such as fog, with significant impacts on road and air safety. We will be interested in exploiting these potentials through industry or government collaboration but rely on NSERC Discovery grant support for the fundamental research needed to initiate and support the more applied studies.