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Performance of Ray Fins in Performance of Ray Fins in Fish LocomotionFish Locomotion
Qiang Zhu and Kourosh Shoele
Department of Structural EngineeringUniversity of California San Diego
Characteristics of Ray FinsCharacteristics of Ray Fins
Characteristics: Structural lightness Deployability Multi-dimensional controllability 3D anisotropic flexibilty
Ray fins of bluegill sunfish (Alben et al. 2007)
rays
membrane
base
branches
tendonsCartilage pad
ligament
dorsal fin
pectoral finpelvic fin
anal fin
caudal fin
Tangorra et al. 2007
Lauder Lab Videos
Fluid-Structure Interaction ModelFluid-Structure Interaction ModelPotential flow model with boundary element
methodWakes are modeled as shear layers and
mathematically represented by distributions of dipoles
Valid in high Reynolds numbersNonlinear Euler-Bernoulli beam model for
embedded raysFully-coupled fluid-structure interactions
Zhu et al. JFM 2002, Zhu & Kourosh JEB 2008
Caudal Fin DynamicsCaudal Fin Dynamics
Advantages of a fin with flexible rays:Reduced lateral force
Increased propulsion efficiency
Reduced dependence on kinematic parameters
Achievement of different locomotion modes (homocercal, heterocercal)
Zhu & Kourosh JEB 2008
Pectoral Fins in Labriform Swimming
Thorsen et al. 2005
Shape and structure
Rigid Rays: All the rays are rigid (red lines)Fin A: All the rays have the same stiffness (green lines)Fin B: The ray at the leading edge is strengthened (blue lines)
Kourosh & Zhu JEB 2009, 2010
Kinematics
Flapping+rowing+baseline rotation
SummarySummaryThe ray-fin structure enables detailed control of fin
motion (since each ray can be controlled individually), and is essential to the performance of the fin in locomotion.
Flexibility of the rays may enhance fin performance. It, however, depends upon detailed distribution of the stiffness (e.g. reinforcement at the leading edge).
Broader ViewBroader ViewOther Skeleton-Reinforced Membranes in NatureOther Skeleton-Reinforced Membranes in Nature
Venation structure in the wing of a Manduca sexta (from Combes & Daniel 2003).
Insect Wings Cell Membrane
Cell membrane contains a lipid bilayer supported by a protein scaffold (the cytoskeleton) (T. Wittmann, Science Photo Library).
Mollusk Nacre
Mollusk (e.g. abalone) nacre contains a chitin network that controls the growth and mechanical properties of the shell (Asaro & Harley 2004).
Zhu et al. Biophy. J 2007; Zhu & Asaro Biophy. J. 2008; Peng et al. Phys. Review E. 2010
This study is supported by NSF.
Acknowledgements