Biomedical subjects

J Abshagen

Publications and source records attributed to J Abshagen.

4 recordsLinked to original sources

PubMed2004

Chaos from Hopf bifurcation in a fluid flow experiment.

Results of an experimental study of a Hopf bifurcation with broken translation symmetry that organizes chaotic homoclinic dynamics from a T2 torus in a fluid flow as a direct consequence of physical boundaries are presented. It is shown that the central features of the theory of Hopf bifurcation in O(2)-symmetric systems where the translation symmetry is broken are robust and are appropriate to describe the appearance of modulated waves, homoclinic bifurcation, Takens-Bogdanov point, and chaotic dynamics in a fluid flow experiment.

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PubMed2003

Standing waves in flow between finite counterrotating cylinders.

Experimental evidence for standing waves resulting from a supercritical Hopf bifurcation that appears as the first pattern-forming instability in counterrotating Taylor-Couette flow is presented. Depending on the aspect ratio two different types of standing waves, denoted as SW0 and SW(pi), could be observed. Both modes have an azimuthal wave number m=1 but differ in symmetry. While for SW(pi), a spatiotemporal glide-reflection symmetry could be found, SW0 is purely spatial reflection symmetric. The transition between the two modes is found to be organized in a cusp bifurcation unfolded by variations of the aspect ratio. The "classical" spiral vortex flow appears in this control parameter regime only as a result of a secondary steady bifurcation from SW0. This transition is found to be either subcritical or supercritical. The experimentally observed bifurcation structure has been predicted by theory of Hopf bifurcation to spiral vortex flow in finite counterrotating Taylor-Couette systems.

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PubMed2001

Gluing bifurcations in a dynamically complicated extended flow.

We report the results of the first experimental study of imperfect gluing bifurcations in an extended fluid flow. It is shown that the central features of the theory are robust and are appropriate to describe the dynamics of a nontrivial physical system. The results include the first experimental evidence for a route to chaos which is an essential part of the theory of imperfect gluing bifurcations.

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PubMed2001

Imperfect homoclinic bifurcations.

Experimental observations of an almost symmetric electronic circuit show complicated sequences of bifurcations. These results are discussed in the light of a theory of imperfect global bifurcations. It is shown that much of the dynamics observed in the circuit can be understood by reference to imperfect homoclinic bifurcations without constructing an explicit mathematical model of the system.

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