Dynamics of Compressible Vortex Rings and Circular Jets

摘要 提案编号：CTS-9622302主要研究者：Virk/Hussain 本文是一个对不可压缩和可压缩两种流动状态下的圆形湍流射流进行数值模拟的项目。 目的是研究不可压缩射流中的旋涡结构，然后将其扩展到研究可压缩性在流动发展中的作用。 涡环是湍流射流中的典型拟序结构。 它们的过渡和相互作用是湍流射流中卷吸和混合的主要原因。 本文研究的问题是非线性演变和转捩过程中的涡度拓扑结构以及转捩后的结构。 复杂的螺旋波分解将被用来揭示导致转捩的涡量包的分离。 将建立一个数值数据库，以便研究转捩机制、利用流入扰动的可控性、远场相干结构的动力学和激波涡流相互作用。 将开发一个有限体积代码，以启动空间演变的三维射流的系统研究。 低马赫数的单频扰动模拟将用于确定实验观察到的周期性/混沌过渡流态的涡动力学。 这项工作的结果将用于改善低维动态模型，使流量控制。 超音速喷流的轴对称模拟将用于确定激波单元结构对相干结构卷起和相互作用的影响。 这将扩展到全三维的，空间上不断变化的，超音速射流的涡动力学方面的研究，以了解相干结构动力学和它们的过渡，以及远场相干结构的演化动力学冲击的影响。 可压缩湍流在技术上是重要的。 这项研究将提供洞察力，将导致计算模型，将能够考虑到流动不稳定性的压缩性的影响，并将奠定基础的流动控制方法的发展。

ABSTRACT Proposal Number: CTS-9622302 Principal Investigator: Virk/Hussain This is a project to carry out numerical simulations of circular turbulent jets in both the incompressible and compressible flow regimes. The aim is to study vortical structures first in incompressible jets and then extend this to the study of the role of compressibility in flow development. Vortex rings are the canonical coherent structures in turbulent jets. Their transition and interactions are the primary cause of entrainment and mixing in turbulent jets. The issues of interest in this study are the vorticity topology during non-linear evolution and transition, and the post transition structure. The complex helical wave decomposition will be used to reveal the separation of vorticity packets that lead to transition. A numerical data base will be developed that will allow the study of transition mechanisms, controllability using inflow perturbations, the dynamics of far field coherent structures and shock vortex interactions. A finite-volume code will be developed to initiate systematic studies of spatially evolving 3D jets. Low Mach number simulations of a single frequency perturbation will be used to determine the vortex dynamics responsible for the experimentally observed periodic/chaotic transitional flow regimes. The results of this effort will be used to improve low-dimensional dynamic models that will enable flow control. Axisymmetric simulations of supersonic jets will be used to determine the effects of shock-cell structure on coherent structure roll-up and interactions. This will be extended to the study of fully 3D, spatially evolving, supersonic jets in terms of vortex dynamics to understand the effects of shocks on coherent structure dynamics and their transition, as well as the evolutionary dynamics of the far field coherent structures. Compressible turbulent flows are technologically important. This study will provide insight that will lead to computational models that will be c apable of taking into account the effect of compressibility on flow instability and will lay the foundations for the development of flow control methods.