Collaborative Research: Dynamical Processes Driving the Genesis and Maintenance of Tornadic Vortices

这项研究将侧重于对导致龙卷风涡旋产生和维持的动力学进行调查。研究的主要假设如下：初级龙卷风涡旋附近较小的(亚龙卷风尺度)涡旋结构经历陀螺仪驱动的对准，随后是一个广义的合并过程。这导致龙卷风环流外缘的涡度梯度自然变陡。最终，这将涡旋与湍流引起的侵蚀过程隔离开来。然后，隔离过程使龙卷风涡旋能够达到用传统数值模式难以模拟的强度，即使分辨率被认为足以分解该涡旋。智能优点：准二维传统大气动力学理论中没有很好地描述导致涡旋孤立的过程。相反，这项研究采用了一种新的理论框架，该框架基于N-S方程(流体力学-HD)与电磁(EM)理论的类比。这个框架在计算流体力学(CFD)社区中得到了越来越多的接受，特别是在过去的15年里。这种新方法的一个关键点是利用外部磁场中磁场区域的排列和驱动涡旋湍流与龙卷风涡旋排列(和合并)之间的相似行为。研究从两个方面进行：(1)隔离过程的数值模拟和(2)描述产生隔离的三维尺度相互作用过程的理论发展。将得到基于可分辨涡度结构的涡度后向散射过程的公式。然后，这个新的框架将被内置到数值模式中，用于在没有极端分辨率的情况下模拟龙卷风。更广泛的影响采用EM-HD类比所采用的方法可能会加强对所有大气涡旋动力学的了解，包括那些支配热带气旋的大气涡旋动力学。虽然这将导致对这些复杂过程的更有力的理解，但它也将为未来的调查引入一个简单、直观、总体的框架。两位首席研究人员计划利用这一简化创建新的教学工具，以清晰的方式向普通公众阐明龙卷风形成和维护的复杂性。此外，这项工作将作为催化剂，强调全面的物理背景(包括电磁学基础)的重要性，特别是对那些进入大气科学和流体动力学领域的人。

This research will focus on an investigation of the dynamics resulting in the genesis and maintenance of tornadic vortices. The overarching hypothesis of the study is following: Smaller (subtornado vortex-scale) vortical structures in the vicinity of a primary tornado vortex undergo gyroscopically driven alignment, followed by a generalized merging process. This leads to a natural steepening of the vorticity gradient on the outer edge of the tornadic circulation. Ultimately, this isolates the vortex from turbulence-induced erosion processes. The isolation process then enables the tornado vortex to achieve strengths not easily simulated with traditional numerical models, even with resolution deemed sufficient to resolve that vortex. Intellectual Merit: The processes leading to vortex isolation are not well represented in quasi-two-dimensional traditional atmospheric dynamics theory. Instead, the study adopts a new theoretical framework based on an analogy of the Navier-Stokes equation (hydrodynamics-HD) with electromagnetic (EM) theory. This framework has been growing in acceptance in the computational fluid dynamics (CFD) community, particularly over the last 15 years. One key point in this new approach exploits the analogous behavior between the alignment of magnetic domains within an external magnetic field, and vortical turbulence being driven to alignment (and merging) with the tornado vortex.The research is on two fronts: (1) numerical modeling of the isolation process and (2) theoretical development describing three-dimensional scale interaction processes producing that isolation. A formulation of a vorticity backscatter process based on resolvable vorticity structure will be resulted. This new framework will then be built into the numerical model used to enable the simulation of a tornado without extreme resolution. Broader Impacts The adopted methodologies embracing an EM-HD analogy will likely enhance understanding of all atmospheric vortex dynamics, including those that govern tropical cyclones. While this will result in a more robust comprehension of these complex processes, it will also introduce a simple, intuitive, overarching framework for future investigations. The two principal investigators plan to take advantage of this simplification to create new teaching tools that articulate the complexities of tornado formation and maintenance in a clear manner to the general public. Additionally, this work will serve as a catalyst for stressing the importance of a well-rounded physics background (including the fundamentals of electromagnetism), especially for those entering the fields of atmospheric science and fluid dynamics.