11 research outputs found
Numerical investigation of a bio-inspired underwater robot with skeleton-reinforced undulating fins
In this paper, the propulsion performance of a bio-inspired underwater robot with a pair of ray-supported undulating pectoral fins is numerically investigated with a fully coupled fluid-structure interaction model. In this model, the flexible fin rays are represented by nonlinear Euler-Bernoulli beams while the surrounding flow is simulated via solving the Navier-Stokes equations. Kinematically, each pectoral fin is activated independently via individually distributed time-varying forces along each fin ray, which imitate effects of tendons that can actively curve the fin rays. We find that the propulsion performance of the bio-inspired robot is closely associated with the phase difference between the leading edge ray and the trailing edge ray of the pectoral fin. The results show that with a symmetrical kinematics, the highest thrust is created when the phase difference is 90 degree while the point maximizing the propulsion efficiency varies with the motion frequency. It is also found that there is a minimum frequency of generating net thrust for a specific parameter setup, which rises as the increase of phase difference. Compared with the symmetrical kinematics, the non-symmetrical kinematics generates more complicated hydrodynamic forces and moments which may be beneficial for the turning maneuver
3D locomotion biomimetic robot fish with haptic feedback
This thesis developed a biomimetic robot fish and built a novel haptic robot fish system based on the kinematic modelling and three-dimentional computational fluid dynamic (CFD) hydrodynamic analysis. The most important contribution is the successful CFD simulation of the robot fish, supporting users in understanding the hydrodynamic properties around it
Distributed sensing in flexible robotic fins: propulsive force prediction and underwater contact sensing
There is recent biological evidence that the pectoral fins of bluegill sunfish are innervated with nerves that respond to bending, and these fish contact obstacles with their fins. However, it is not known how fin-intrinsic sensing could be used to mediate propulsion and touch in engineered fins. The objective of this thesis is to understand the use of distributed sensing in robotic fins, inspired by bony fish fins, for the prediction of propulsive forces and for the discrimination between fluidic loading and contact loading during underwater touch. The research integrates engineering and biology and builds an understanding of fin-intrinsic sensing through study of swimming fish and robotic models of fish fins and sensors. Multiple studies identify which sensor types, sensor placement locations, and model conditions are best for predicting fin propulsive forces and for predicting the state of contact. Comparisons are made between linear and nonlinear Volterra-series convolution models to represent the mapping from sensory data to forces. Best practices for instrumentation and model selection are extracted for a broad range of swimming conditions on a complex, multi-DOF, flexible fin. This knowledge will guide the development of multi-functional systems to navigate and propel through complex, occluded, underwater environments and for sensing and responding to environmental perturbations and obstacles.Ph.D., Mechanical Engineering and Mechanics -- Drexel University, 201
A numerical study of fin and jet propulsions involving fluid-structure interactions
Fish swimming is elegant and efficient, which inspires humans to learn from them to design
high-performance artificial underwater vehicles. Research on aquatic locomotion has made
extensive progress towards a better understanding of how aquatic animals control their
flexible body and fin for propulsion. Although the structural flexibility and deformation of
the body and fin are believed to be important features to achieve optimal swimming
performance, studies on high-fidelity deformable body and fin with complex material
behavior, such as non-uniform stiffness distributions, are rare.
In this thesis, a fully coupled three-dimensional high-fidelity fluid-structure interaction (FSI)
solver is developed to investigate the flow field evolution and propulsion performance of
caudal fin and jet propulsion involving body and/or fin deformation. Within this FSI solver,
the fluid is resolved by solving unsteady and viscous Navier-Stokes equations based on the
finite volume method with a multi-block grid system. The solid dynamics are solved by a
nonlinear finite element method. The coupling between the two solvers is achieved in a
partitioned approach in which convergence check and sub-iteration are implemented to
ensure numerical stability and accuracy. Validations are conducted by comparing the
simulation results of classical benchmarks with previous data in the literature, and good
agreements between them are obtained.
The developed FSI solver is then applied to study the bio-inspired fin and jet propulsion
involving body deformation. Specifically, the effect of non-uniform stiffness distributions of
fish body and/or fin, key features of fish swimming which have been excluded in most
previous studies, on the propulsive performance is first investigated. Simulation results of a
sunfish-like caudal fin model and a tuna-inspired swimmer model both show that larger
thrust and propulsion efficiency can be achieved by a non-uniform stiffness distribution (e.g.,
increased by 11.2% and 9.9%, respectively, for the sunfish-like model) compared with a
uniform stiffness profile. Despite the improved propulsive e performance, a bionic variable
fish body stiffness does not yield fish-like midline kinematics observed in real fish,
suggesting that fish movement involves significant active control that cannot be replicated
purely by passive deformations.
Subsequent studies focus on the jet propulsion inspired by squid locomotion using the
developed numerical solver. Simulation results of a two-dimensional inflation-deflation jet
propulsion system, whose inflation is actuated by an added external force that mimics the
muscle constriction of the mantle and deflation is caused by the release of elastic energy of
the structure, suggest larger mean thrust production and higher efficiency in high Reynolds
number scenarios compared with the cases in laminar flow. A unique symmetry-breaking
instability in turbulent flow is found to stem from irregular internal body vortices, which
cause symmetry breaking in the wake. Besides, a three-dimensional squid-like jet propulsion
system in the presence of background flow is studied by prescribing the body deformation
and jet velocity profiles. The effect of the background flow on the leading vortex ring
formation and jet propulsion is investigated, and the thrust sources of the overall pulsed jet
are revealed as well.
Finally, FSI analysis on motion control of a self-propelled flexible swimmer in front of a
cylinder utilizing proportional-derivative (PD) control is conducted. The amplitude of the
actuation force, which is applied to the swimmer to bend it to produce thrust, is dynamically
tuned by a feedback PD controller to instruct the swimmer to swim the desired distance from
an initial position to a target location and then hold the station there. Despite the same
swimming distance, a swimmer whose departure location is closer to the cylinder requires
less energy consumption to reach the target and hold the position there.Fish swimming is elegant and efficient, which inspires humans to learn from them to design
high-performance artificial underwater vehicles. Research on aquatic locomotion has made
extensive progress towards a better understanding of how aquatic animals control their
flexible body and fin for propulsion. Although the structural flexibility and deformation of
the body and fin are believed to be important features to achieve optimal swimming
performance, studies on high-fidelity deformable body and fin with complex material
behavior, such as non-uniform stiffness distributions, are rare.
In this thesis, a fully coupled three-dimensional high-fidelity fluid-structure interaction (FSI)
solver is developed to investigate the flow field evolution and propulsion performance of
caudal fin and jet propulsion involving body and/or fin deformation. Within this FSI solver,
the fluid is resolved by solving unsteady and viscous Navier-Stokes equations based on the
finite volume method with a multi-block grid system. The solid dynamics are solved by a
nonlinear finite element method. The coupling between the two solvers is achieved in a
partitioned approach in which convergence check and sub-iteration are implemented to
ensure numerical stability and accuracy. Validations are conducted by comparing the
simulation results of classical benchmarks with previous data in the literature, and good
agreements between them are obtained.
The developed FSI solver is then applied to study the bio-inspired fin and jet propulsion
involving body deformation. Specifically, the effect of non-uniform stiffness distributions of
fish body and/or fin, key features of fish swimming which have been excluded in most
previous studies, on the propulsive performance is first investigated. Simulation results of a
sunfish-like caudal fin model and a tuna-inspired swimmer model both show that larger
thrust and propulsion efficiency can be achieved by a non-uniform stiffness distribution (e.g.,
increased by 11.2% and 9.9%, respectively, for the sunfish-like model) compared with a
uniform stiffness profile. Despite the improved propulsive e performance, a bionic variable
fish body stiffness does not yield fish-like midline kinematics observed in real fish,
suggesting that fish movement involves significant active control that cannot be replicated
purely by passive deformations.
Subsequent studies focus on the jet propulsion inspired by squid locomotion using the
developed numerical solver. Simulation results of a two-dimensional inflation-deflation jet
propulsion system, whose inflation is actuated by an added external force that mimics the
muscle constriction of the mantle and deflation is caused by the release of elastic energy of
the structure, suggest larger mean thrust production and higher efficiency in high Reynolds
number scenarios compared with the cases in laminar flow. A unique symmetry-breaking
instability in turbulent flow is found to stem from irregular internal body vortices, which
cause symmetry breaking in the wake. Besides, a three-dimensional squid-like jet propulsion
system in the presence of background flow is studied by prescribing the body deformation
and jet velocity profiles. The effect of the background flow on the leading vortex ring
formation and jet propulsion is investigated, and the thrust sources of the overall pulsed jet
are revealed as well.
Finally, FSI analysis on motion control of a self-propelled flexible swimmer in front of a
cylinder utilizing proportional-derivative (PD) control is conducted. The amplitude of the
actuation force, which is applied to the swimmer to bend it to produce thrust, is dynamically
tuned by a feedback PD controller to instruct the swimmer to swim the desired distance from
an initial position to a target location and then hold the station there. Despite the same
swimming distance, a swimmer whose departure location is closer to the cylinder requires
less energy consumption to reach the target and hold the position there
Underwater Vehicles
For the latest twenty to thirty years, a significant number of AUVs has been created for the solving of wide spectrum of scientific and applied tasks of ocean development and research. For the short time period the AUVs have shown the efficiency at performance of complex search and inspection works and opened a number of new important applications. Initially the information about AUVs had mainly review-advertising character but now more attention is paid to practical achievements, problems and systems technologies. AUVs are losing their prototype status and have become a fully operational, reliable and effective tool and modern multi-purpose AUVs represent the new class of underwater robotic objects with inherent tasks and practical applications, particular features of technology, systems structure and functional properties
Design of a Novel Concept for Harnessing Tidal Stream Power: A Continuation
The Water Energy Harvester MQP provides design insight into a novel system that collects energy from flowing water. This project is a continuation of a previous MQP which initialized the basic design for a tidal turbine. The new design is comprised of a single neoprene fin. The fin and powertrain designs have been redeveloped for greater power transfer, energy collection efficiency, and manufacturability. The power efficiency of the device was not found, the unloaded cut-in speed was measured as 0.7 m/s. It was determined that a lighter, continuous fin is necessary for smoother motion and for reducing the torque needed during its sinusoidal motion. The crankshaft requires manufacturing that is exceptionally difficult on WPIâs campus and may also require use of a different material
Fluid Mechanics of Plankton
The cooperation between plankton biologists and fluid dynamists has enhanced our knowledge of life within the plankton communities in ponds, lakes, and seas. This book assembled contributions on planktonâflow interactions, with an emphasis on syntheses and/or predictions. However, a wide range of novel insights, reasonable scenarios, and founded critiques are also considered in this book
Exploring the biofluiddynamics of swimming and flight
cum laude graduation (with distinction