421 q-vortexと乱流の相互作用(S35-1 乱流渦構造(1),S35 乱流渦構造)  [in Japanese] 421 Interaction between g-vortex and turbulence  [in Japanese]

The interaction between a columnar vortex and external turbulence is investigated numerically. The q-vortex is immersed in an initially isotropic homogeneous turbulence field, which itself is produced numerically by a direct numerical simulation of decaying turbulence. The formation of turbulent eddies around the columnar vortex and the vortex-core deformations are studied in detail by visualizing the flow field. In the less-stable case with q=-1.5, small thin spiral structure is formed inside the vortex core. In the unstable case with q=-0.45, the linear unstable modes grows until the columnar vortex make one turn. Its growth rate agrees with that of the linear analysis[1]. After the vortex made two turns, the secondary instability is excited. It caused that the columnar g-vortex collapses and many fine scale vortices appear abruptly.