Ice cubes can help keep your drink from sloshing out of your glass, a new U of A study suggests – and could protect Arctic ice shelves from climate change.
University of Alberta physics professor Bruce Sutherland co-authored a study last month in Physical Review Fluids on how floating particles (simulated bits of ice in this case) can stop waves in their tracks.
Sutherland said he first noticed about 20 years ago how having a layer of foam or ice cubes atop a drink stopped it from sloshing, but never bothered to investigate why.
Two years ago, the topic came up at a conference where ocean researchers were talking about climate change in the Arctic. Researchers were concerned climate warming was melting ice cover, exposing more water to the wind and producing bigger waves. Bigger waves could bash more ice off ice shelves, which would create smaller ice cubes that melted faster, expose more water, and produce even bigger waves. If the broken-up ice around ice shelves somehow affected these waves, this dangerous feedback loop might not come to pass.
Sutherland and University of B.C. mathematician Neil Balmforth decided to test the effects of ice chunks on waves using a tank full of red-coloured salt water and a layer of hydrogel beads to simulate ice chunks. (Actual ice would melt and not hold its shape between trials, which would throw off the results.) They coloured some of the normally transparent beads blue so they could see them. They then sloshed the water in the tank with and without beads in it and filmed the results.
The team found that waves in the tank shrank at a steady pace when there weren’t beads in the water, but stopped abruptly after only a few sloshes when there were beads.
“The ice almost immediately kills the waves,” Sutherland said.
Sutherland said they had similar results when they replaced the beads with artificial snow – essentially the ground-up form of the beads – and with foam from five cans of Guinness beer.
“I did save one (can) for myself,” he noted, and an Irish friend did scold him for pouring out all that beer.
Sutherland and Balmforth believe the secret lies in viscosity, or liquid friction. When waves pass through the beads/ice chunks, the beads repeatedly separate and squish back together, squeezing the water in and out of the spaces between them like an accordion and robbing the wave of energy, causing it to dissipate.
Sutherland said this phenomenon was great news for the Arctic, as it suggests the chunks broken off ice shelves can blunt the impact of future waves and reduce the pace of their breakup.
It also suggests people can prevent spilled drinks by ordering beer with more foam or head, Sutherland said. English bars tend to be messier as they minimize the amount of foam atop their drinks, whereas Belgian ones see fewer spills due to the thick heads on their beer.
“I certainly would love to get funding from Guinness or some other beer company to explore this further,” Sutherland joked, adding he actually did hope to do further tests with the artificial snow (which was a more realistic simulation of broken-up sea ice) later this year.
Celtic Knot bartender Kim Swindells said she slings about 100 drinks a day, about 30 per cent of which typically contain ice. While she had never experienced this effect of ice on waves, she said guests could reduce their risk of spills by using taller glasses and not filling them to the top.
While Sutherland said adding ice to drinks could keep them from spilling, Swindells advised against doing so with beer.
“It’ll completely change the flavour,” she said, as the ice will water it down.
Sutherland’s study is available at bit.ly/2Sigy5B.
