Atmospheric Boundary Layer Studies

大气边界层(ABL)通常是湍流的，典型的深度约为1公里，是我们大多数人生活、工作和娱乐的地方。我的研究小组过去曾使用模型和实地研究来研究与ABL流动相关的许多问题，包括复杂地形上的流动(例如，丘陵和粗糙度变化)。尽管许多研究小组对大气边界层的研究有很长的记录，但在我们对一些重要的实际问题，如雾和地表条件的理解和预测方面，仍有显著改进的机会。 未来5年的一个目标将是研究边界层内的雾，并仔细探索其发展和后来消散的条件。这些过程涉及热量、水(水蒸气和水滴)、辐射(长波和短波)和云物理过程的湍流传输。 另一个重要的应用ABL研究领域是冬季路况研究。除了湍流输送，再加上地面和次表层条件，这在很大程度上可能取决于太阳和长波辐射通量，受低层云的存在有很大影响。例如，与改进的ABL模型相结合，将允许扩展非常广泛使用的Metro预测模型，该模型是17年前在加拿大环境部开发的。 我们的主要方法将继续是湍流边界层模拟。有两种基于计算机的方法，大涡模拟(LES)和求解带有某种形式的湍流闭合的雷诺平均N-S方程(RANS)。我的研究小组过去曾在不同的项目中使用过这两种方法。我们在这里将重点放在RAN建模上，但在某些情况下，LES具有优势，例如，在调查雾“斑块”和车辆尾流情况方面。 我还计划探索RANS模型中的一个详细的闭包问题。一般而言，RANS模式将把湍动能作为变量之一，并将“总长度尺度”L或湍动能耗散率作为另一个变量。这在大多数情况下似乎是令人满意的，并在某种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光谱，然后在光谱中“级联”，在很小的尺度上被耗散并转化为热量(&lt；1 mm)。在某些情况下，如风力涡轮机尾迹或车辆尾迹，在中等尺度(叶片或车辆宽度)有额外的TKE输入。我们将研究有效地代表这一进程的方法。 主要的研究目标将是扩大我的团队擅长的ABL研究的范围，并将辐射效应包括在内。这包括雾等对道路和航空安全有重大影响的应用。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NSERC发现拨款支持启动和支持更多应用研究所需的基础研究。

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.