Near wake structures in a stably stratified fluid using Dynamic Mode Decomposition

Early experiments suggest that early wake information including body geometry and initial conditions in a linearly stratified fluid is lost during the wake evolution process (Meunier and Spedding Phys. Fluids 16, 298-305, 2004). However, limited by the experimental techniques in these early experiments, details of possible pattern memory remain elusive. The current project seeks to evaluate the near wake structures of various body shapes in a stratified fluid using Dynamic Mode Decomposition (DMD) on both experimental and numerical wake data at low Re (200 ≤ Re ≤ 1000) and low Fr (0.5 ≤ Fr ≤ 8). The dominant dynamic modes depend systematically on both Re and Fr. The energy contributions of different modes are further investigated to understand the complex, near wake evolution and identify any retained early wake information.