Abstract
An outline of the state space of planar Couette flow at high Reynolds numbers (Re < 10^4) is investigated via a variety of efficient numerical techniques. It is verified from nonlinear analysis that the lower branch of Hairpin Vortex State (HVS) asymptotically approaches the primary (laminar) state with increasing Re. It is also predicted that the lower branch of HVS at high Re belongs to the stability boundary that initiates transition to turbulence. These facts suggest HVS may provide a criterion to estimate a minimum perturbation arising transition to turbulent states at the infinite Re limit.