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Nonorthodox Behavior of Fish Fins

Intelligent Mechanics (i-mech) in Nature and Design

von Dipl.-Ing. Michael Dienst (Autor)

Wissenschaftlicher Aufsatz 2013 9 Seiten




The paper presents the state of the Systems Biology of rays in fin membranes of fish. The description of the functional geometry of the fin membrane is preceded by an anatomical taxis. Results of calculations and measurements for the mechanics of fin rays are identified.

The aim of bionics is to decipher principles of living nature for to carry in technology and develop clever solutions [Rech-94][Bapp-99][Bech- 97][Nach-98][Nach-00]. System Biology plays a crucial role: It produces the material of which the bionic generates innovations.

The ray-finned fishes are a very successful class of bony fish. To the genuine bony fish include, with approximately 30000 known extant species about 96 percent of all living fish species and about half of all vertebrate species described. Their anatonmie and the mechanics of their musculoskeletal system is the subject of numerous studies. Nevertheless, the considerable diversity of function and design of fin rays, their evolutionary history, the individual growth and differentiation during individual development is little understood.

Assignments of features and functions of the fin rays of different species with different skills and habits, such as hunting, escape, rooting or different swimming styles are still partially unknown. Consider the fish fin in the context of fish body. Fin rays are part of the vertebrate skeleton, which forms a series of solid, articulated (skeletal) elements that are important in cooperation with the muscles for the movement. In light of the evolutionary development of vertebrates, the spinal column is older than any part of the postcranial skeleton. About the origin of the extremities of the fish there despite new fossils, improved methods, sophisti-cated phylogenetic analysis to date, no consensus is among evolutionary biologists [W-01] [W-02] [W-03] [W-04].

In the early 1880s several anatomists postulated that the original vertebrate continuous, paired side fins from the gills had to vent, so- called fin edges [Hild-01]. It was assumed that the fins of modern fishes represent segments of those originally continuous fin edges. Modern fin edges supporting aquatic life are, for example, eels and lampreys. The genome of the sea lamprey has been recently deciphered [W-10]. The fact that lampreys are vertebrates show their inner cartilaginous skeleton and the structure of their brain. Lampreys are the only survivors of an ancient evolutionary line of vertebrates represent.

The visible membrane of fin fish may have been originally supported only in the course of evolution of dermal scales in the skin covering them. The fins of more advanced bone fish were stabilized by a series of slender rays in the inner region. Basically, the rays of the cartilaginous fish are slender, not articulated and elastic and called Ceratotrichia. Fin rays of fish bones are wider geglie amended, proximal pairs, branched distally and ossified and are called Lepidotrichia, they are evolutionarily derived from scales described [W-06][W-06][Hild 01]. The caudal fin is used for propulsion force production, to stabilize the non-driven rectilinear locomotion and maneuvering. If the animal in its fluidic environment locates inhomogeneities, a velocity field or a suitable pressure gradient, the fish can use this to its own mobility.

James Liao of Harvard University in Cambridge (Massachusetts) built a tank for an underwater landscape and examined the swimming behavior of the animals, with affixed electrodes to the fins. They came to the conclusion that the fish moves in a zigzag of eddy to eddy and needed relatively low muscle strength for this type of locomotion [W-07].

The interaction and exchange interaction of transported in a flow vortices with a fin membrane is a fundamental phenomenon of vortex flow and inversion-flow and subject of analysis of active and passive control of vertebrate aquatic species.

The principles of vortex control are of great importance for the understanding of how fish swim and maneuver. By Gopalkrishnan et al (1994), Armed Lien et al (1996) and Anderson (1996), a harmonically oscillating airfoil in a afflicted with large vortices interact favorably when both the eddy size and the frequency of the harmonically oscillating profile fit the harmoniously flow. Fluid-structure interaction of flexible bodies in vortical flows is the subject of extant research [Gopa-94][Read- 02][Ande-99][alb-09] [Liao-06][Tria-02] [Floc 09 ][Stre-96].

Consider the momentum exchange with the medium of the wing membrane of the fish fin. The energy transfer at the fluid-structure interaction can be productive or generative. In a productive interaction the fin couples energy force from the flow into the structure. In a generative fluid-structure interaction, the fin membrane couples energy from the structure into the fluid. Production and generation can take place in a time-locally intertwined, complex overall process.

Unlike technology, where the energy and information exchange in powerwings can be clearly described and assigned, the biological wing constructions provides a complex, for feedback and adaptation enabled multifunctional systems. These are optimized and able to control their fluid environment, interact with them and condition them for their transport and mobility issues. Lauder sum up, that in a swirling flow transported vortices the fluid-structure interaction is generative with a fin membrane, when the timing of body motion is synchronal with the shape of a Karman vortex street. The fluid-structure interaction of a vertebra with a fin membrane is productive generative, when the timing of body motion is synchronal with the shape of a inverted Karman vortex street. Periodicity, frequency, phase and direction of the vortex flow has a significant impact on the quality of the fluid-structure interaction with the fin membrane. From the point of view of bionics, adaptive foils are a way of passive flow control. This makes a profound research required.

In several research projects at the Beuth University of Applied Sciences Berlin, since 2006 biologistic backgrounds "intelligent mechanics" we considered the fundamental solution for auto-adaptive profiles of biological fins. First technical intelligent kinematics were designed in 2005 [MIR 05], numerical approaches in 2008 [KRE -08], systems with fluid-structure interaction were investigated [Sie-10], [Sie-11] and patents on adaptive load components were developed [USP-12][DeP-11]. Numerical models of fluid-structure interaction only exist for selected conditions. As part of future research, projects will aim to a process chain to develop the solutions of body deformation (finite element method, FEM) and flow field (computational fluid dynamics CFD) in a common simulation approach under the special conditions of highly complex dynamic couples (Fluid Structure Interaction FSI). Simulation and calculation results represent the basis for the design of real flow components.



ISBN (eBook)
ISBN (Buch)
523 KB
Institution / Hochschule
Beuth Hochschule für Technik Berlin – Bionik
bionics ray-finned fisch intelligent mechanics


  • Autor: undefined

    Dipl.-Ing. Michael Dienst (Autor)

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Titel: Nonorthodox Behavior of Fish Fins