Dynamic Mode Decomposition for Reduced-Order Kinematic and Aerodynamic Analysis in Straight Flight of the Great Roundleaf Bat

Presenter: Kamol Banik, Mechanical Engineering

Authors: K.Banik, D.Tafti

Abstract: Bats serve as biological models for agile micro-air vehicles due to their articulated skeletons and flexible wing membranes that enable controlled shape changes. However, bat wing deformations carry high dimensional complexity that challenges for analysis and control. We use Dynamic Mode Decomposition (DMD), a data-driven reduced-order method, to analyze straight-flight kinematics of the great roundleaf bat (Hipposideros armiger) and the associated aerodynamics. DMD approximates temporal dynamics through a linear evolution operator where each mode/structure is associated with a single frequency and growth rate. Applying DMD to time-resolved marker kinematics, we isolate three dominant bands: a near-zero component (mean), a fundamental flapping mode, and a super harmonic “twisting” band. Reconstructions using only these dominant frequency bands reveal that the twisting band increases instantaneous wingspan and planform area relative to the flapping band alone. Coupled high-fidelity CFD driven by the band-limited reconstructions shows that twisting elevates cycle-averaged lift compared with flapping reconstructions. These results show that twisting plays a key role in bat flight performance and provides important insights for bio-inspired MAV design.