Formulating a theoretical scaling for dispersion in MHD turbulence

湍流最基本的方面之一是弥散--一种衡量颗粒如何扩散的指标。在空气和水等电中性流体中，弥散决定了水分、颗粒或化学物质如何混合到大气或海洋中。其他液体，如液态金属和等离子体，可以带电。它们的运动被磁场的存在从根本上改变，并用磁流体动力学来描述。当等离子体在星际介质中扩散时，磁流体中的弥散决定了空间天气的性质，恒星核心的化学物质如何混合到其外层，以及粒子如何被困在反应堆的液态金属毯子中。该项目的目标是清楚地了解在空气或水中观察到的流体动力情况下，磁流体动力弥散与弥散有何不同。该项目将包括暑期研究学生，使用科学可视化和计算机渲染的计算物理扩展计划，以及针对科学/工业工作人员的技术培训。该项目将利用现代思想和理论技术来修改和扩展由Richardson于1926年为流体动力学流体开发的弥散理论，以应用于磁流体流体环境。测试我们的新预测将需要特别密集的模拟；这些模拟将在世界上一些最大的超级计算机上进行。模拟数据将使我们的理论结果能够探索磁流体动力学湍流的基础性问题。这些包括湍流如何形成首选的运动方向，以及流动的不同部分如何相互作用。我们的理论和计算调查结果将使工程师能够设计更高效的反应堆，使天文学家能够更好地预测影响地球生命的空间天气。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

One of the most fundamental aspects of turbulent flows is dispersion – a measure of how particles spread out. In electrically neutral fluids such as air and water, dispersion determines how moisture, particulates, or chemicals mix into the atmosphere or oceans. Other fluids, like liquid metals and plasmas, can carry an electrical charge. Their movement is fundamentally changed by the presence of magnetic fields and is described by magnetohydrodynamics. Dispersion in magnetohydrodynamic fluids determines the properties of space weather as plasma spreads in the interstellar medium, how chemicals from the core of a star are mixed into its outer layers, and how particles are trapped in the liquid metal blankets of reactors. The goal of this project is to provide a clear understanding of how magnetohydrodynamic dispersion differs from dispersion in the hydrodynamic case observed in air or water. This project will include summer research students, a computational physics outreach program using scientific visualizations and computer renderings, and technical training for the scientific/industrial work force.This project will leverage modern ideas and theoretical techniques to modify and extend the theory of dispersion, developed by Richardson in 1926 for hydrodynamic fluids, to the setting of magnetohydrodynamic fluids. Testing our new prediction will require simulations that are particularly intensive; these simulations will be performed on some of the largest supercomputers in the world. The simulation data will allow our theoretical results to probe questions of foundational importance for magnetohydrodynamic turbulence. These include how a turbulent flow develops a preferred direction of movement, and how different parts of the flow interact energetically. The results of our theoretical and computational investigation will allow engineers to design more efficient reactors, and astronomers to better predict the space weather that impacts life on Earth.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.