Low Reynolds number modal stability analysis of the 6-1 prolate spheroid

Asymmetric flow fields in symmetric flow configurations can be observed in a wide range of applications such as diffusers, bumps, jets in crossflow, and wakes of both slender and bluff bodies. Despite the importance of these flow configurations in aerospace, maritime, and transportation engineering, the mechanisms that give rise to asymmetries are generally underappreciated and poorly understood.

We use global stability analysis of the low Reynolds number flow field around the prolate spheroid to study possible asymmetries in the flow field. First, at zero angle of attack, the aspect ratio (between 1 and 6) and Reynolds number are varied simultaneously. Second, for the 6-1 spheroid, the angle of attack is varied between 0 and 90 degrees while the Reynolds number is also changed. Two types of modes are found: stationary asymmetric and shedding modes. The structure of the base flow and the eigenmodes, as well as additional metrics such as structural sensitivity, are analyzed in detail.