On the Recurrence Signatures of Flapping Wings Exposed to Gusty Simple Shear Flow

The primary aim of the research reported in this paper was to understand the effect of change of gusty simple shear inflow’s gradient on the force and moment patterns of a flapping wing in the 3D reference frame. A wing undergoing one degree of freedom asymmetric flapping and rectangular planform shape was considered. The gradient of the gusty simple shear inflow profile, V_grad, was varied from –10 to +10 in steps of 5 and corresponding vertical and horizontal forces and moment about the flapping axis were computed. Time series of these forces and moment were used to plot the global recurrence plots and were compared. Quantitative analysis of the findings was carried out by the windowed recurrence quantification analysis of the force and moment patterns. Eight recurrence parameters, viz. recurrence rate, determinism, laminarity, trapping time, ratio, entropy, maximum line and trend were calculated and compared. Numerical investigations revealed that negative gusty shear gradient induced a considerable increase in vertical force and moment and marginally decreased the horizontal forces. Positive gusty shear gradient induced a marginal increase in horizontal forces but caused a substantial decrement in vertical force and moment.