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: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=681458
• 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释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，表面涂料，抑制，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气相湍流的强烈影响。湍流对液滴运动的影响取决于液滴惯性和大小相对于湍流的长度和速度尺度。一般而言，湍流会导致液滴在整个流动中的扩散，并以在混合和耗散量表下生成间歇性液滴浓度区域的方式。对上述过程的分析很有价值。申请人是UNB研究团队的成员，重点关注开发的大型涡流模拟（LES）工具，用于跟踪大气下层中的农药液滴，从释放到地面盖上的沉积。 LES模拟了覆盖1平方公里的局部地形上的大气湍流，已使用在UNB上开发的高级基于GPU的计算来完成。当前的挑战是通过大气湍流开发出有效，准确的液滴运动模型。作为重要贡献提供的文章之一描述了通过拉格朗日液滴跟踪对飞机唤醒的模拟。下一个研究目标是LES模拟，其中包括飞机唤醒和大气湍流，以及欧拉（Eulerian）的液滴传输模型。 ***目前的赠款提案描述了一个实验研究计划，这对于支持上述较大的目标是必要的。它提供了湍流中液滴浓度和转运的测量，以测试和开发基于欧拉LES的计算模拟中使用的现象学转运模型。将要研究的模型问题是在各向同性网格湍流中的水平轴对称喷雾羽流，其模型尺度可以近似于大气近地面层的大涡流模拟的尺度。将选择液滴尺寸，以扩大文献中目前考虑的Stokes数字和沉降速度的范围，以包括与农药运输相关的速度。实验将与大气湍流的LES模拟中的模型测试协调。 **