CFD Based Investigation on the Hydroplaning Mechanism of a Cormorant’s Webbed Foot Propulsion

Abstract

Aquatic unmanned aerial vehicles (AquaUAV) have aroused much attention from researchers, though no fully-featured aerial-aquatic UAV exists so far. The assistance of webbed foot hydroplaning can accomplish rapid takeoff of a cormorant. A significant impact force and moment can be generated due to the webbed foot propulsion in the water-to-air transition. However, the change law of force and moment experienced by the cormorant during takeoff has not been captured. Based on previous achievements in the biological investigation, we developed a biomimetic prototype with curve fitting model and parameter optimization to attain specific movements to imitate cormorant's hydroplaning strategy. The bionic webbed foot considers the elastic mechanics, and the forepart is regarded as flexible material for fluid-structure interaction (FSI). Dynamic process of rapid takeoff in the aspects of flow characteristics and mechanical properties can be estimated by computational fluid dynamics (CFD) in our proposed FSI model, which establishes a foundation for further applications in the design of the assisted propulsion system of aerialaquatic UAV. INDEX TERMS Biomimetics, computational biophysics, fluid dynamics, coupled mode analysis, military aircraft.

Biorobotic Waterfowl Flipper with Skeletal Skins in a Computational Framework: Kinematic Conformation and Hydrodynamic Analysis

“…Conceptually, the flexibility and potency of the cormorant flippers are considered the foremost features for an optimal swimming performance. We previously studied the high-speed flapping motion of the cormorant flippers during the water surface takeoff, [15][16][17] in which the flippers are modeled as solid bodies or piece models. To handle the oscillatory motions of the biomimetic flippers with a strong resemblance, we need to investigate the dynamic musculoskeletal architecture modeling with compliant mechanics.…”

The hydrodynamic performance of duck feet for submerged swimming resembles oars rather than delta-wings

“…Consequently, the faster moving and broader base of the trailing edge affects a greater mass of water thus generating most of the drag used as propulsive force 18 , 19 . The hydrodynamics of the avian webbed foot has been previously studied with respect to drag-based vortex formation on rigid plates 20 or as a flexible flipper 21 , 22 for biomimetic surface swimming, hydroplaning and takeoff from water 23 – 26 . However, the hydrodynamic functioning of the foot while swimming underwater should differ from these conditions at the water surface due to differences in paddling kinematics, body orientation and the need to resist buoyancy when the body is entirely submerged.…”

Cormorant Webbed-feet Support Water-surface Takeoff: Quantitative Analysis via CFD

“…The numerical computational investigation is more superior to obtain the laws of flow field evolution and visually analyze the real-time eddy dynamics processes of the interaction between organisms and the surrounding fluid [25，26]. It can dispose of the biological locomotion mobility and adaptability in turbulent fluid [27] and across fluid domains (flying fish [28], squid [29], water birds [30][31][32][33], et al).…”