Dolphin propulsion, mushroom urine sensors, and Roman ship repairs

Ars Technica’s monthly science roundup surfaces six stories that didn’t get standalone coverage in April. The headline item: University of Osaka researchers ran supercomputer simulations of dolphin swimming and resolved a long-standing question about how the animals generate thrust so efficiently. Their results, published in Physical Review Fluids, show that large vortex rings produced by the initial tail flap do nearly all the propulsive work, while the cascade of smaller eddies that follows is just turbulent byproduct contributing nothing to forward motion.

Co-author Susumu Goto frames the finding as evidence that the hierarchy of vortices in turbulent flow is what matters for understanding biological swimming. The team wants to apply the same vortex-scale analysis to underwater robotics, where current designs don’t exploit the large-vortex thrust mechanism dolphins rely on. The other roundup items span Roman shipbuilding archaeology, mushrooms that respond to human urine, and a soda-can crushing experiment.