Daydreams & Doodles

Exploratory physical models and demonstrations in biomechanics, fluid dynamics, and passive dynamics

Status: Experimental

A curated collection of interesting physics and biology topics. Currently one entry; additional examples may be added over time.

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Daydreams & Doodles

Exploratory physical models and demonstrations in biomechanics, fluid dynamics, and passive dynamics

Research

Dead Fish Swimming Upstream

This demonstration shows a dead fish propelled upstream through vortex-induced oscillation. The phenomenon illustrates how passive body geometry can interact with structured fluid flow to produce net propulsive forces without active muscular input. Beal et al. (2006) demonstrated that compliant bodies placed in the Kármán vortex street behind a cylinder can extract energy from the flow and move upstream, a result consistent with earlier observations by Liao et al. (2003) showing that live trout reduce muscle activity when exploiting vortex wakes.

Primary sources: Beal et al. (2006), Passive propulsion in vortex wakes; Liao et al. (2003), Fish exploiting vortices decrease muscle activity.

The comparison with mechanical drift is an editorial analogy, not evidence that the two systems share a causal mechanism. Fluid-structure interaction, a prescribed wake, and a compliant fish body are materially different from a declared multibody golf model.