Droplet Transport in Flow Turbulence

湍流中的液滴传输

• 批准号: RGPIN-2016-04148
• 负责人: Holloway, Gordon
• 金额: $ 1.89万
• 依托单位: University of New Brunswick
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=709009
• 关键词: Droplet; Transport; Flow; Turbulence

Dilute poly-disperse mixtures of small liquid droplets in gas phase flow is a common feature of both environmental and industrial processes. For example: clouds, humidification and cooling, combustion, surface coating, fire suppression, drug delivery, and pesticide application. In many practical cases the droplets are small enough that their motion is strongly influenced by the gas phase turbulence. The effect of turbulence on the droplet motion depends on the droplet inertia and size relative to the length and velocity scales of the turbulence. In general terms, turbulence causes a diffusion of droplets across the flow and in such a manner as to generate intermittent regions of droplet concentration at the mixing and dissipation scales. Prediction methods for droplet concentration and its transport based on Computational Fluid Dynamics are valuable to the analysis of the above mentioned processes. The applicant is a member of a research team at UNB focussed on development a Large Eddy Simulation (LES) tool for tracking pesticide droplets in the lower layer of the atmosphere from release to deposition on the ground cover. LES simulation of the atmospheric turbulence over local topography covering 1 sq km has been accomplished using advanced GPU based computing developed at UNB. The present challenge is developing an efficient and accurate model of droplet motion through the atmospheric turbulence. One of the articles provided as a significant contribution describes a RANS simulation of an aircraft wake with Lagrangian droplet tracking. The next research objective is a LES simulation which includes the aircraft wake and atmospheric turbulence together with an Eulerian model of droplet transport. The present grant proposal describes an experimental research program which is necessary to support the larger objectives described above. It provides measurements of droplet concentration and transport in turbulent flow for the purposes of testing and developing phenomenological transport models used in Eulerian LES based computational simulations. The model problem that will be studied is a horizontal axisymmetric spray plume in isotropic grid turbulence with model scales chosen to approximate the scales of a Large Eddy Simulation of the near ground layer of the atmosphere. The droplet sizes will be chosen to extend the range of Stokes number and settling velocity currently considered in the literature to include those of relevance to pesticide transport. The experiments will be coordinated with model testing in LES simulations of atmospheric turbulence.

气相流中小液滴的稀多分散混合物是环境和工业过程的共同特征。例如：云、加湿和冷却、燃烧、表面涂层、灭火、药物输送和农药施用。在许多实际情况下，液滴足够小，以至于它们的运动受到气相湍流的强烈影响。湍流对液滴运动的影响取决于相对于湍流的长度和速度尺度的液滴惯性和尺寸。一般而言，湍流导致液滴在流动中扩散，并以这样的方式在混合和消散尺度上产生液滴集中的间歇区域。 基于计算流体动力学的液滴浓度及其传输预测方法对于上述过程的分析具有重要价值。申请人是新布伦伯勒大学研究小组的成员，该研究小组致力于开发大涡模拟（LES）工具，用于跟踪大气下层农药液滴从释放到沉积在地被植物上的整个过程。使用 UNB 开发的基于 GPU 的先进计算技术完成了 1 平方公里局部地形大气湍流的 LES 模拟。当前的挑战是开发一种高效、准确的大气湍流中液滴运动模型。其中一篇作为重要贡献的文章描述了使用拉格朗日液滴跟踪对飞机尾流进行 RANS 模拟。下一个研究目标是 LES 模拟，其中包括飞机尾流和大气湍流以及液滴传输的欧拉模型。 本拨款提案描述了一项实验研究计划，该计划对于支持上述更大的目标是必要的。它提供了湍流中液滴浓度和传输的测量，用于测试和开发基于欧拉 LES 的计算模拟中使用的唯象传输模型。将研究的模型问题是各向同性网格湍流中的水平轴对称喷雾羽流，其模型尺度选择近似大气近地面层大涡模拟的尺度。将选择液滴尺寸以扩大目前文献中考虑的斯托克斯数和沉降速度的范围，以包括与农药运输相关的那些。这些实验将与大气湍流 LES 模拟中的模型测试相协调。