Dynamics and Statistics of Worms around a Calumnar Vortex

数值研究了圆柱涡与外部湍流的相互作用。一个Lamb-Oseen涡沉浸到最初各向同性的均匀湍流，这本身，是由一个衰减湍流的直接数值模拟数值产生的。通过流场的可视化，详细研究了柱状涡周围非均匀湍流细涡的形成和涡核的变形。最初的随机湍流涡（蠕虫）缠绕在柱状涡周围，并成为涡环（或螺旋）。统计量，如两点能量谱和两点涡度拟能谱，通过平均20个实现，并与理论预测进行了比较。快速畸变理论（RDT）。在涡面附近，轴向速度相关性占主导地位，而径向速度相关性变得更大，在那里的蠕虫被包裹。当柱涡较外部湍流强时，外部速度扰动被柱涡阻挡，不能直接穿透涡核，而外部压力扰动则激发出各种类型的涡波（Kelvin波）。

The interaction between a columnar vortex and external turbulence is investigated numerically. A Lamb-Oseen vortex is immersed into initially isotropic homogeneous turbulence, which, itself, is produced numerically by a direct numerical simulation of decaying turbulence. The formation of inhomogeneous fine turbulent eddies around the columnar vortex and the vortex-core deformations are studied in detail, by visualizing the flow field. The initially random turbulent eddies (worms) are wrapped around the columnar vortex, and become like vortex rings (or sprirals). Statistical quantities, such as two-point-energy-spectrum and two-point-enstrophy spectrum, are evaluated by averaging 20 realizations and compared with the theoretical predictions by a. rapid distortion theory (RDT). The axial velocity correlation dominates near the vortex surface, whereas the radial velocity correlation becomes larger, where the worms are wrapped. If the columnar vortex is strong compared with the external turbulence, external velocity disturbances are blocked by the vortex and they cannot penetrate into the vortex core directly, whereas various types of vortex waves (Kelvin waves) are excited by the external pressure disturbances.