Fluid thinking

This fringe event converted the foyer of the academic institution Imperial College London into an interactive adult learning zone for the evening. Huge widescreen televisions displaying colourful animations were coupled with engaging scientists keen to tell visitors what they do everyday in their laboratories, and why it’s important. There

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was no lack of imagination on the stalls: the Japanese Suminagashi printing technique was enrolled to help describe blood flow imaging in the heart, while under the Christmas tree, members of the public knitted blood vessels to help explain how vessels react to high blood pressures. It wasn’t all blood and heart cavities; fluid was moving from wine glasses into mouths as well, and many other demonstrators were explaining how the dynamics of fluid movement help us understand a wealth scientific processes. Below are just a few:

Liquid Rock

Pummel stones you use in the bath and the granite you might chop your vegetables on are made from the same material, and start out as exactly the same molten rock flowing and swelling around below a volcano. The molten rock, or magma, has very high viscosity and so can trap large amounts of gases such as carbon dioxide, silicon dioxide and steam. When a volcano erupts due to the movement of tectonic plates, the gases

expand in the same way that a bottle of lemonade will fizz if you shake it. Because the rock is being forced to the cooler surface it rapidly solidifies with the gas bubbles still expanding inside so you’re left with the very light-weight pummel stones that are full of holes. Granite also starts as magma but, because it cools very slowly because the volcano doesn’t erupt, almost all the gas escapes from the liquid over time and so large solid crystals form. This is why granite is much denser and harder than pummel stone can be fashioned to have a very smooth surface.

Waste water

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Machine used to test coagulation in water treatment

The reason water is dirty is usually because it contains small organic particles. Luckily, almost all of these organic particles are negatively charged so an effective way to treat water is to add a positively charged substance. Ferric Sulphate is very positively charged and when it’s added to the dirty water, it pulls in the negative organic particles so they clump together. This doesn’t happen all at once. Mixing the water in the right way will produce the right fluid movement that causes the most effective coagulation. The coagulated particles then drop to the bottom of the tank as sediment and the water is siphoned off and filtered.

Turbulence

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The viscosity of the fluid in these snow globes decreases from left to right

Levels of turbulence can be measured in snow globes containing liquids of different viscosity. If the liquid is viscous, the ‘snow’ will move slowly and take longer to settle and as the viscosity decrease, the  turbulence increases and the snow settles quicker. In a very low viscosity fluid like water, the snow settles fastest but an interesting change occurs when a polymer is added to the most viscous fluid as the polymer makes the fluid non-Newtonian. In a Newtonian fluid, the molecules face the same amount of resistance in all directions. Polymers only allow movement in one direction so when they are added to the viscous fluid and the snow globe is shaken up, the polymer molecules act like elastic and rebound the energy of the snow particles, which keeps them moving around the globe. As the particles are moving faster the turbulence increases and snow settles more quickly. Richard Feynman called turbulence “the most important unsolved problem of classical physics” and studying it helps our understanding of the surface of the sun, vehicle aerodynamics and weather patterns.

Fluid in foods

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Two sodium polymers join together. The mesh they form traps water molecules and makes jelly

Jelly: When two special Sodium polymers are put into a solution containing positive ions, the negative parts of the polymers attract towards the same positive ions in the solution and, when they come into close contact with each other, the polymers bind together to form a mesh. Common jelly is just the water that gets trapped within this mesh while it formed.

 

Cornflour: Mixed with water, this forms a non-Newtonian fluid called ‘oobleck’. One characteristic of oobleck is that the viscosity changes depending on the amount of force applied. If a large force is applied, it solidifies and resists the force. A small force will make the oobleck give way and move just like a liquid. Check out the video of oobleck being struck with a hammer.

The Imperial College Fringe event was an easy, friendly and entertaining way to learn about science. In just an hour and a half, I found out about volcanos, liquid nitrogen, blood movements, turbulence and much more from a group enthused and interested professionals in the field. Would recommend the event to anyone who enjoys being entertained through surprise and wonder.

Fluid Thinking took place at Imperial College London on 12 December 2013.

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