use a specialized swimming pattern called the “Kármán gait” to capture energy from swirling water currents, reducing their necessary muscle activity by nearly 50%. Rather than actively fighting turbulent river flows, these fish masterfully surf the vortex streets created behind rocks and logs to maintain their position with minimal effort. What is a Kármán Vortex Street?
When a steady water current hits a stationary object—like a boulder, tree branch, or river piling—the fluid cannot pass smoothly around it. Instead, the water separates and breaks off into a highly predictable, alternating pattern of swirling eddies. This double row of staggered, spinning vortices is known in physics as a Kármán vortex street. The Mechanism: The Kármán Gait
For decades, researchers assumed fish simply hid directly behind rocks to take advantage of the slower water velocity (a tactic known as “drafting”). However, fluid dynamics studies spearheaded by researchers like Dr. James Liao revealed a far more active, elegant phenomenon called tuning.
[ River Boulder ] —> Flow Direction ( @ ) ( @ ) ( @ ) <– Kármán Vortices/ / `–> ( <)))>< ) –> ( <)))>< ) <– Trout “Slaloming” Passive Wave
Instead of swimming with normal, energy-intensive muscle undulations, the trout alters its entire body mechanics: Body Uses Vortices to Save Energy — Biological Strategy
Leave a Reply