Turbulence--Cloud Interactions: Laboratory and Field Studies

湍流--云相互作用：实验室和现场研究

• 批准号: 0535488
• 负责人: Raymond Shaw
• 金额: --
• 依托单位: Michigan Technological University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-10-15 至 2010-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0535488&HistoricalAwards=false
• 关键词: Turbulence; Cloud; Interactions; Laboratory; Field

A basic underlying assumption for most of our treatment of the physics of clouds is that drops are distributed in space in a perfectly random manner at sub-grid scales. It has been recognized for some time now that this assumption is clearly violated at cloud edges where entrainment takes place, but the impact of turbulence on drop spatial distributions in cloud interiors, and hence on our understanding of cloud physical processes, has only recently come under intensive scrutiny. The suggestion from theoretical and modeling studies that turbulence should "cluster" drops has proven difficult to confirm from in-cloud observations, mostly because of sampling problems with in situ devices. Wind tunnel experiments performed by the principle investigator seem to provide some support for clustering in that environment. This grant supports continued laboratory studies to investigate the impact of turbulence on drop spatial distributions in well-characterized conditions, with particular emphasis on how this applies to the collision-coalescence process. The principle investigator will use high spatial resolution, high digital resolution, and short exposure Charge Coupled Device (CCD) cameras to make measurements of the three-dimensional spatial distribution of drops using inline holography in a laboratory turbulence chamber. The turbulence chamber will be larger such that the turbulence Reynolds number inside will be closer to and the energy dissipation rates similar to those found in the atmosphere. The flow inside the chamber will be characterized with particle image velocimetry. The spatial distribution of drops, together with the turbulence characterization, allows for investigations of the dependence of clustering on drop size and turbulent intensity. A further addition of a high speed digital camera, loaned from the Max Planck Institute for Dynamics and Self Organization in Germany, will allow measurement of the drop relative velocity distribution, thus closing the measurements needed to evaluate the generalized collection kernel. The laboratory results will be evaluated, and extended to high turbulence Reynolds number regimes, in natural clouds using the same inline holographic system.Broader Impacts: This work has broad potential impact as it spans the fields of atmospheric sciences and engineering multiphase flows. The principle investigator has strong collaborative ties with people in the engineering multiphase flow community, and thus benefits from and acts as a conduit to the atmospheric sciences community of the greater engineering expertise in multiphase flows. This experimental work is a critical contribution to a field where theoretical and modeling work has outpaced our observational abilities. The principle investigator has a well-established track record working with undergraduate students, which he hopes to continue with this grant, and will also support one graduate and one post-doctoral student.

我们对云的物理处理的一个基本的潜在假设是，雨滴在空间中以一种完全随机的方式在亚网格尺度上分布。一段时间以来，人们已经认识到，在发生夹带的云边缘，这一假设显然是违反的，但是湍流对云内部液滴空间分布的影响，以及对我们对云物理过程的理解，直到最近才受到严格的审查。从理论和模型研究中得出的湍流应该“聚集”液滴的建议已被证明很难从云内观测中得到证实，主要是因为原位设备的采样问题。首席研究员进行的风洞实验似乎为这种环境下的聚类提供了一些支持。该基金支持持续的实验室研究，以调查湍流在特征良好的条件下对液滴空间分布的影响，特别强调如何将其应用于碰撞-合并过程。主要研究者将使用高空间分辨率、高数字分辨率和短曝光电荷耦合器件（CCD）相机，在实验室湍流室中使用在线全息术测量液滴的三维空间分布。紊流室将更大，使内部的紊流雷诺数更接近于大气，能量耗散率与大气相似。用粒子图像测速法对腔室内的流动进行表征。液滴的空间分布，连同湍流特性，允许研究聚类对液滴大小和湍流强度的依赖。从德国马克斯普朗克动力学和自组织研究所借来的高速数码相机，将允许测量液滴的相对速度分布，从而完成评估广义集合核所需的测量。实验室结果将被评估，并扩展到高湍流雷诺数制度，在自然云中使用相同的内联全息系统。更广泛的影响：这项工作具有广泛的潜在影响，因为它跨越了大气科学和工程多相流领域。首席研究员与工程多相流社区的人们有着密切的合作关系，因此受益于并充当了大气科学界在多相流方面更大的工程专业知识的渠道。在这个理论和建模工作已经超过我们的观测能力的领域，这项实验工作是一个关键的贡献。首席研究员在与本科生合作方面有着良好的记录，他希望通过这笔资助继续下去，并将支持一名研究生和一名博士后。