Local and Global Stability Analysis on Flows around a SD7003 Airfoil

Laminar separation and subsequent transition to turbulent flow plays an important role in the performance of airfoils operating at low Reynolds number (Re<10). For better understanding of the formation and turbulent breakdown of laminar separation bubbles (LSB), both local and two-dimensional global linear stability analysis are applied to investigate the stability of a CFD time-averaged non-parallel flowfield over a SD7003 airfoil at Reynolds number 6×10. The flow is found to be unstable at all wavenumbers examined. The most unstable modes from local and global stability analysis are close to each other, and the frequency of this mode is in agreement with CFD results. Spatial structures of the disturbances at most unstable modes are discussed. By applying the stability analysis, the temporal flow structures of the LSB can be examined with the most unstable modes of global stability results.