Many fishes use undulatory fin to propel themselves in the underwater environment. These locomotor mechanisms have a popular interest to many researchers. In the present study, we perform a three-dimensional unsteady ...Many fishes use undulatory fin to propel themselves in the underwater environment. These locomotor mechanisms have a popular interest to many researchers. In the present study, we perform a three-dimensional unsteady computation of an undulatory mechanical fin that is driven by Shape Memory Alloy （SMA）. The objective of the computation is to investigate the fluid dynamics of force production associated with the undulatory mechanical fin. An unstructured, grid-based, unsteady Navier-Stokes solver with automatic adaptive remeshing is used to compute the unsteady flow around the fin through five complete cycles. The pressure distribution on fin surface is computed and integrated to provide fin forces which are decomposed into lift and thrust. The velocity field is also computed throughout the swimming cycle. Finally, a comparison is conducted to reveal the dynamics of force generation according to the kinematic parameters of the undulatory fin （amplitude, frequency and wavelength）.展开更多
Fishes interact with the fluid environment using various surfaces.These multiple control surfaces work in combination to produce the thrust and the balance torques in a steady swimming,to maneuver and to position them...Fishes interact with the fluid environment using various surfaces.These multiple control surfaces work in combination to produce the thrust and the balance torques in a steady swimming,to maneuver and to position themselves accurately even in turbulent flows.These motivate us to embark on a research program designed to develop an agile biologically inspired robotic fish based on the performance of multiple fins.To accomplish this goal,a mechanical ray-like fin actuated by the shape memory alloy (SMA) is developed,which can realize the oscillating motion,the undulating motion or even the complex three dimensional motion.The basic unit is the two opposite side SMA-driven plate,namely the fin ray.As a result,a lightweight bio-inspired fin is constructed by placing radially multiple SMA fin rays.A biologically inspired underwater vehicle (BIUV) is later built using the above multiple lightweight bio-inspired fins.Two common arrangement styles of multiple fins on the BIUV are considered here:one is the posterior fin (for the oscillating motion) that is parallel to the anterior fins (for the undulating motion),another one is the posterior fin that perpendicular to the anterior fins.The kinematic modeling,the deformation modeling and the detecting of the SMA fin are made.The thrust generation is also established.Finally,an experiment is conducted to test the performance of the proposed two arrangement styles,including the comparison of the averaged propulsion velocity and the averaged thrust under certain kinematic parameters.Meanwhile,the influence of the frequency and the amplitude of the SMA fin ray on the propulsion performance is also investigated.展开更多
文摘Many fishes use undulatory fin to propel themselves in the underwater environment. These locomotor mechanisms have a popular interest to many researchers. In the present study, we perform a three-dimensional unsteady computation of an undulatory mechanical fin that is driven by Shape Memory Alloy （SMA）. The objective of the computation is to investigate the fluid dynamics of force production associated with the undulatory mechanical fin. An unstructured, grid-based, unsteady Navier-Stokes solver with automatic adaptive remeshing is used to compute the unsteady flow around the fin through five complete cycles. The pressure distribution on fin surface is computed and integrated to provide fin forces which are decomposed into lift and thrust. The velocity field is also computed throughout the swimming cycle. Finally, a comparison is conducted to reveal the dynamics of force generation according to the kinematic parameters of the undulatory fin （amplitude, frequency and wavelength）.
文摘Fishes interact with the fluid environment using various surfaces.These multiple control surfaces work in combination to produce the thrust and the balance torques in a steady swimming,to maneuver and to position themselves accurately even in turbulent flows.These motivate us to embark on a research program designed to develop an agile biologically inspired robotic fish based on the performance of multiple fins.To accomplish this goal,a mechanical ray-like fin actuated by the shape memory alloy (SMA) is developed,which can realize the oscillating motion,the undulating motion or even the complex three dimensional motion.The basic unit is the two opposite side SMA-driven plate,namely the fin ray.As a result,a lightweight bio-inspired fin is constructed by placing radially multiple SMA fin rays.A biologically inspired underwater vehicle (BIUV) is later built using the above multiple lightweight bio-inspired fins.Two common arrangement styles of multiple fins on the BIUV are considered here:one is the posterior fin (for the oscillating motion) that is parallel to the anterior fins (for the undulating motion),another one is the posterior fin that perpendicular to the anterior fins.The kinematic modeling,the deformation modeling and the detecting of the SMA fin are made.The thrust generation is also established.Finally,an experiment is conducted to test the performance of the proposed two arrangement styles,including the comparison of the averaged propulsion velocity and the averaged thrust under certain kinematic parameters.Meanwhile,the influence of the frequency and the amplitude of the SMA fin ray on the propulsion performance is also investigated.
