Hydrodynamic Simulations of Relativistic Flows: From Pulsars to Parsec-Scale Jets

气体喷流，以接近光速的速度流动，是我们宇宙的一个共同特征，在黑洞等致密物体捕获物质的地方都能找到。在这个项目中，将使用对这些喷流的计算机模拟来促进我们对这种能量流的理解。特别是，这些模拟将帮助我们了解这种喷气式飞机如何不受干扰地穿透它们的环境，并阐明产生它们的“引擎”的性质。这项研究中使用的技术结合了狭义相对论，并使用了最初为航空航天工程等领域设计的最先进的方法。它允许用有限的计算机资源执行大型计算，从而允许对问题的许多方面进行探索。其中包括：冲击波如何在气流中形成，气流对冲击致密周围材料的反应，或由于发动机喷嘴方向的变化而在空间中旋转的情况。这项研究的一个重要方面是，它提供了对恒星双星系统中鲜为人知的喷流的探测，并应该揭示这些喷流在多大程度上真正是迷你类星体--活动星系的缩小版本。同样的技术也适用于脉冲星风产生的星云，在脉冲星风中，通过周围介质的移动会导致星云被扫回气体尾巴，类似于银河系和恒星喷流。了解这些“风星云”将提供对脉冲星本身流动的洞察，而脉冲星本身并不能直接观测到。

AST 0205105HughesJets of gas, flowing at close to the speed of light, are a common feature of our Universe and are found wherever compact objects such as black holes capture material. In this project, computer simulations of these jets will be used to advance our understanding of such energetic flows. In particular these simulations will be designed to help us understand how such jets can penetrate their environment without disruption and also shed light on the nature of the `engines' which produce them. The technique used in this study incorporates Special Relativity and uses state-of-the-art methods originally designed for fields such as aerospace engineering. It enables large computations to be performed with modest computer resources, thus allowing an exploration of many facets of the problem. Among these are: how shock waves form in the gas flow, and how the flow responds to impacting dense surrounding material, or being spun around in space due to changes in the direction of the engine's nozzle. An important aspect of the study is that it provides a probe of the poorly understood jets of stellar binary systems, and should reveal the extent to which these really are mini-quasars -- scaled down versions of active galaxies. The same technique is applied to the nebulae that result from pulsar winds, where moving through the ambient medium causes the nebula to be swept back into a tail of gas, similar to the galactic and stellar jets. Understanding these `wind nebulae' will provide insight into the flow from the pulsar itself, which is not directly observable.***