Estimation of nonlinear surface pressure characteristics of aerofoil: A 0-1 test approach

We investigate the nonlinear behaviour of the surface flow over a two-dimensional NACA 2415 airfoil undergoing turbulent inflow having 8.46% TI at Re=3.01×105 using the 0-1 test for chaos. It clearly identifies the overall surface flow changes and also finds the transitions from regular to chaotic behaviour over the airfoil surfaces. 0-1 test for chaos has been successfully applied to study the subsequent transitions associated with the flow mechanisms like flow bifurcation at the leading-edge, acceleration of the flow that propagates from the curved surfaces, splitting, merging and rolling up of vortices near the vicinity of the trailing edge. In our present study, the 0-1 test for chaos just takes the input as a time series data, measured simultaneously over the airfoil surfaces to obtain the translational dynamics in phase space by using the variables p(n) and q(n) and the asymptotic growth rate (K) calculated from the translation behaviour of variables. The translational variables take a value 0 or 1, based on the underlying dynamics of the system as regular or chaotic. Our study states that, 0-1 test for chaos seems to be efficient in accurately predicting the underlying dynamics of the surface flow induced over the airfoil under aperiodic conditions.