Dipan Deb | Searcharxiv

arXiv2025

Vortices, turbulence, and center of pressure in flow over pitching swept wings

This study examines the center of pressure (CoP) movement of rigid pitching swept wings based on prior measurements by (Zhu, Breuer, 2023}. The wings analyzed feature sweep angles of $0^{\circ}$, $10^{\circ}$, and $20^{\circ}$, and are subjected to large amplitude sinusoidal pitching instabilities below a critical torsional spring stiffness. The CoP location is determined from time-resolved force and moment measurements, revealing minimal variation in the cross-chord direction but significant spanwise and chord-wise movement, varied by sweep angle. The trajectory of the CoP varies with sweep angle due to the evolving strength and dynamics of the leading edge and tip vortices. The Force Moment Partitioning Method (FMPM) is applied to stereo Particle Image Velocimetry (PIV) data to identify contributions from wing kinematics, vortex structures, and viscous effects. This approach elucidates the roles of leading edge and tip vortices, as well as the periodic and stochastic components of the flow field, in influencing the net forces and moments.

physics.flu-dyn↗

arXiv2023

Thrust Enhancement and Degradation Mechanisms due to Self-Induced Vibrations in Bio-inspired Flying Robots

Whenever a flapping robot moves along a trajectory it experiences some vibration about its mean path. Even for a hovering case, a flier experiences such vibration due to the oscillatory nature of the aerodynamic forces. In this paper we have studied the effect of such vibration on hovering. We used two setups to measure thrust force generated by flapping robots. One involving loadcell, which does not allow any kind of vibration. The other one involves a pendulum which allows vibration at a particular direction. We used two different flapping robots; one is a traditional flapping robot with two wings and the other one is a four wings robot which exploits clap and peel mechanism to generate thrust. We observed that the loadcell setup measures more thrust for the two wings model than the pendulum setup. The opposite trend was observed for the four wings model. We measured the vibration induced velocity using motion capture system. We used well known aerodynamic models to observe the effect of the vibration during the flapping cycle. To gain physical insight into the vibration affected flow field, we used smoke flow visualization at different instances during the flapping cycle. It revealed that the perturbation ebbs a jet effect in case of the two wings which leads to its adverse effect for thrust generation. On the contrary the perturbation enhances the clapping effect for the four wings robot, resulting favorable for thrust generation.

physics.flu-dyn↗