アーメッドボディ後方に生成される渦構造の非定常挙動とその遷移機構に関する研究

抄録

The Ahmed body, which is a rectangular parallelepiped body with a rounded front edge and a slanted base, shows drastic change of aerodynamic drag at 30° of the slanted base. This phenomenon is caused by the critical change of the wake structure, i.e. the three-dimensional separation (TDS) state in the range below 30° and the quasi-axisymmetric separation (QAS) state in the range above 30°. However, the detailed mechanism of the occurrence of the transition has not been clarified. Then, we measured the unsteady behaviour of the wake structure around rear part of the body with the dynamic PIV system to capture the transient change, production, entrainment, interaction, coalescence and breakup of the vortex structures. Based on above results, the fluid dynamical mechanism which induces the transition of the wake structure at the critical angle of the slanted base is discussed.