Wake Interactions of Multiple Foils Pitching in Line
Inspired by the interactions between the fish dorsal and caudal fins, this work aims to investigate the interaction effects of multiple foils in a tandem configuration. With phase differential between neighboring foils used as key parameters, the hydrodynamic performance is looked into and the corresponding wake structures are mapped out in a phase dim. The result shows that, instead of a coherent '2S' wake pattern, sometimes a branched '2P' wake pattern can achieve higher thrust and propulsive efficiency at the same time. This may be used to explain why some fishes doing long-distance migration generate a '2P' wake pattern in their downstream.
Median-Fin Interactions in Fish-Like Locomotion
By utilizing the interactions among median fins (the dorsal, anal and caudal fins), fishes can achieve higher thrust and efficiency during its forward swimming. Using a three-dimensional bluegill sunfish model, this work conducted a systematic study on the dorsal/anal fin effects on the caudal fin performance and body trunk drag force. The phase-leading dorsal and anal fins with larger area is observed to increase the propulsive efficiency of the caudal fin significantly (by about 50%) and reduce the trunk drag force by debilitating interactions between the left- and right-stroke posterior body vortices.
Kinematics and Hydrodynamics of a Dolphin in Forward Swimming
Dorsoventral undulation is widely adopted by aquatic mammals for propulsion. As one of the excellent swimmers, dolphins are well known for its capabilities of performing high-efficiency cruising. Using the video graphic technique and virtual skeleton-based surface reconstruction method, a three-dimensional high-fidelity computational model is obtained for the swimming dolphin. Kinematic analysis is
performed on this computational model to achieve the time-varying kinematics of the dolphin, and CFD simulation is conducted to look into the corresponding hydrodynamics and wake structures. This work aims to bring new insight into understanding the force generation mechanisms of dorsoventral swimming and offer potential suggestions for the future designs of unmanned underwater vehicles.
Kinematics and Hydrodynamics of Burst-and-Coast Swimming
Burst-and-coast swimming, which consists of several active burst swimming bouts and a passive motionless coast swimming phase, is widely observed in many fish species. This swimming mode has long been believed to be a strategy fish adopted to save energy during its forward locomotion. With the motion of a burst-and-coast swimming trout reconstructed from high-speed videos, the kinematics and hydrodynamics of burst-and-coast swimming are studied. The paper is under preparation and will be submitted soon.
Energetics of Intermittent Swimming Gait in Fish-Like Locomotion
With the continuous and intermittent swimming kinematics extracted from live swimming rainbow trout, simulations are conducted to look into the effects of the intermittent swimming gait on the energetics and hydrodynamic forces in fish-like swimming. The instantaneous velocity and hydrodynamic force generation, as well as the vorticity field are looked into to disentangle the underlying energy saving mechanisms of the intermittent swimming.
Optimal Foil Shape Design in Efficient Flapping Propulsion
In nature and engineering applications, air/hydrofoils possess a vast array of shapes which are suited to the flow regimes in which the foils typically operate. Recent studies on the effects of foil shape in unsteady hydrodynamic propulsion indicate that changing the foil shape can impact the propulsive efficiency significantly. In this work, we use two geometric parametrization methods and a gradient-based optimization scheme to design the foil shape targeting at high propulsive efficiency in unsteady propulsion. Both parametrization methods yield a foil shape with thick forebody and tapered trailing edge, of which the efficiency exceeds the NACA0012 foil by about 22%.
Aerodynamics and Pharyngeal Wall Collapsibility in Sleep Apnea
Why do Fish School?
