Dynamics and Statistics of Worms around a Calumnar Vortex

对柱状涡与外部湍流的相互作用进行了数值研究。Lamb-Osee涡被浸入初始各向同性的均匀湍流中，这种湍流本身是通过对衰减湍流的直接数值模拟而产生的。通过对流场的可视化，详细研究了柱状涡周围非均匀细湍涡的形成和涡核变形。最初随机的湍流涡旋(蠕虫)包裹在柱状涡旋周围，并变得像涡环(或螺旋)。对两点能谱和两点能化谱等统计量进行了平均20种实现，并与快速失真理论(RDT)的理论预测进行了比较。涡面附近的轴向速度相关性占优势，而涡面附近的径向速度相关性较大，在涡面附近有蠕虫包裹。如果柱状涡与外部湍流相比较强，则外部速度扰动被涡旋阻挡，不能直接进入涡核，而各种类型的涡波(开尔文波)则由外部压力扰动激发。

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.