一様減衰乱流に及ぼすヘリシティと座標回転の効果(<小特集>:渦)

抄録

To consider the non-reflection property of the turbulence subjected to system rotation, a new method was proposed to introduce turbulence helicity into an isotropic turbulent flow field for direct numerical simulation (DNS). The effects of the helicity and the rotation on turbulence statistics and vortical structure were investigated by theoretical analysis and DNS of the homogeneous decaying turbulence. The DNS results show that both the rotation and the helicity inhibit the energy decaying. The theoretical analysis shows very different mechanisms for the rotation and the helicity to produce this effect, i.e. the helicity directly decreases the energy transfer while the rotation suppresses the energy transfer due to the so called scrambling effect. The rotation elongates the vortical structure along the rotation axis, and it a appears to weaken this tendency with the presence of the helicity.