Linear instability in the wake of an elliptic wing

Wake Dynamics of Finite Aspect Ratio Wings. Part III: TriGlobal Linear Stability Analysis

“…The TriGlobal instability analysis results at the two Reynolds numbers are presented as columns in the same figure. The most striking feature of the 3D eigenmodes at both sets of conditions is that they couple together linear instability mechanisms, such as trailing-vortex or wake instability, which have been treated in isolation in earlier analyses [13]. The leading damped eigenmode at Re = 100, obtained by the Residuals Algorithm [19], is shown in the middle row (left column) of Figure 5.…”

“…The methodology employed for the present analyses follows closely the earlier works of He et al [2,13], who addressed linear instability in the wake of a three-dimensional wing with elliptical planform [13], as well as primary and secondary instability of spanwise homogeneous flow in the wake of stalled wings with different NACA profiles [2]. These analyses used the Nek5000 [14] and nektar++ [15] open source codes, respectively, both of which will also be employed presently in order to cross-validate the results obtained.…”

“…In the context of laminar separated flows, the discovery of a three-dimensional self-excited global mode in a steady laminar (two-dimensional) separation bubble [12] set in motion a series of papers across speed regimes, aiming at understanding phenomena such as low-frequency "breathing" of separated flows, or the so-called "stall cells" associated with massive separation on airfoils from a linear global fluid flow instability perspective. To-date limited work exists [13] in the literature that has applied a fully three-dimensional (TriGlobal) linear stability analysis to flow around a wing and the present effort aims at closing this gap.…”

Special issue on global flow instability and control

“…On the theme of stability, TriGlobal stability analyses of flows past a freely rotating sphere [9], the wake of a three-dimensional wing [13] and boundary layers perturbed by streamwise vortices [20] are discussed. A unified perspective of instability in rotating Bödewadt, Ekman and von Kármán layers has been presented [7].…”

Stability of Low-Reynolds-Number Separated Flow Around an Airfoil Near a Wavy Ground

“…Another unique aspect of the present study concerns the introduction of three-dimensionality to this problem, through the use of global flow stability analysis. To develop effective control strategies to suppress flow separation and improve aerodynamic performance requires a sound understanding of the instability characteristics of the base flow [12][13][14][15][16][17][18]. Linear stability analysis has been used to successfully predict the primary stability of two-and three-dimensional flows [19].…”