Closed laboratory? Go to the kitchen – ScienceDaily

Zenit’s answer eventually came to pancakes. He teaches in a fluid dynamics lab class at Brown University, and an experiment requires students to measure viscosity, which is often done by measuring the rate at which small spheres fall through thick liquids and sink to the bottom. But Zenit understood that he didn’t have to do it that way. The kitchen is full of viscous fluids, and all he had to do was pick one.

Why not pancake batter?

This fall, the students in his class, wherever they were seized, had to mix pancake batter, pour it onto a horizontal surface, and measure how fast the beam expanded. “By measuring the rate at which this blob grows over time, it is possible to calculate viscosity backwards,” said Zenit.

Zenit described the experiment during a mini-symposium on kitchen flows at the American Physical Society’s 73rd Annual Meeting of the Fluid Dynamics Division. In addition to his project on stickiness through pancakes, the symposium included new research on how fluids mix with each other and how they incorporate solid particles (such as in batter or dough). Researchers at the University of Cambridge have described new discoveries in hydraulic jumps, those oddly smooth circles of water, surrounded by turbulence, that form directly under a running kitchen tap.

Chemical engineer Endre Mossige, postdoctoral researcher at Stanford University, organized the symposium. “Kitchen flow experiments are so easy to do,” he said. “You need so little equipment to extract such useful information on fluid dynamics.”

The kitchen is a natural place to look for inspiration, said Jan Vermant, engineer at ETH Zurich. “In the kitchen we do a lot with high interface materials,” he said. “You have to mix fluids and air, make emulsions and work with bubbles. This is a fundamental problem of food projects, known by chefs all over the world”.

Vermant reported on his group’s recent work, which tackled a beer problem by turning it into a fluid dynamics problem. He studies thin films and in recent research has studied the stability of foam in beers and breads. Brewers, he said, monitor the fermentation trend of new beers by observing the stability of the foam. But, he said, the process is very “hand wavy”. When he started looking at brewing through the lens of fluid dynamics, he found a rich research environment.

Beer bubbles contain a rich variety of environments: capillary streams, soap films and protein aggregation. “Basically, they have all the mechanisms that you can design as an engineer,” he said. His team discovered, to their surprise, that even though most beers have foam, different beers have different mechanisms behind those foams. Some foams act like soap films; others develop robust protein webs on the surface.

“Each of them appropriately highlights different aspects of the problem,” Vermant said. In subsequent work, his group closely analyzed interfacial phenomena in loaves and similarly discovered a variety of behaviors. “They have this rich diversity of mechanisms for stabilizing foam structures,” he said.

Vermant said the work isn’t just about beer and bread; it can also serve as an inspiration for new materials. “We can mimic these systems and we could produce foams using the same principles as beer foams,” he said, which could be useful for applications ranging from spray isolation to crop protection foams.

At Brown, Zenit said not all of the students successfully completed the experiment. “Some of them took my advice too literally and did it in a hot pan,” he said. Cooking the pancake changed the viscosity, freezing the batter in place, which meant the students had no usable data. (But they had breakfast.)

He said switching to pancakes during the pandemic opened his eyes to several ways to teach core ideas like stickiness. “In regular experiments, you drop this sphere into a container and measure it,” he said. The fluid, he says, is reduced to its size. With batter, the student experiences the concept. “With pancakes, you can feel the stickiness.”