A floating ice block moves on water thanks to its own melting.

Inclined bottoms create underwater jets as cold meltwater sinks, pushing the block. Could iceberg motion be partly self-driven?

🔗 https://physics.aps.org/articles/v19/36

#IcePhysics #FluidFlow #SelfPropulsion #MeltingDynamics #Oceanography

Melting Can Propel Icebergs

Icebergs have long served as a metaphor for not knowing what’s going on beneath the surface. Studies like today’s are a reminder of why that is. Researchers found that asymmetric icebergs–shaped, in this case, like a right triangular prism–can self-propel as they melt. Their shape forces cold, dense meltwater to slide down the surface, generating a sinking plume that propels the ice as a whole. The team demonstrated this effect in both fresh- and saltwater. For icebergs wandering into warm waters, the effect is particularly strong and may reach levels about 10% of the magnitude of dominant propulsive forces like wind. (Image and research credit: M. Berhanu et al.; via APS)

Ice Discs Surf on Herringbones

Inspired by the roaming rocks of Death Valley, researchers went looking for ways to make ice discs self-propel. Leidenfrost droplets can self-propel on herringbone-etched surfaces, so the team used them here, as well. On hydrophilic herringbones, they found that meltwater from the ice disc would fill the channels and drag the ice along with it.

But on hydrophobic herringbone surfaces, the ice disc instead attached to the crest of the ridges and stayed in place–until enough of the ice melted. Then the disc would detach and slingshot (as shown above) along the herringbones. This self-propulsion, they discovered, came from the asymmetry of the meltwater; because different parts of the puddle had different curvature, it changed the amount of force surface tension exerted on the ice. Thus, when freed, the ice disc tried to re-center itself on the puddle.

The team is especially interested in how effects like this could make ice remove itself from a surface. After all, it requires much less energy to partially melt some ice than it does to completely melt it. (Image and research credit: J. Tapochik et al.; via Ars Technica)

#fluidDynamics #ice #melting #physics #science #selfPropulsion #superhydrophobic