Guest Blogger: Hannah Fix

by Michael Mullaney on September 11, 2012

(Senior Hannah Fix wrote this excellent post for The Approach to tell us about her educational outreach work with Professor Patrick Underhill. Enjoy!)

My name is Hannah Fix, I am a  senior undergraduate studying aeronautical and mechanical Engineering. I work with Professor Patrick Underhill on the “Fluid Dynamics Demo Kit: Fluid Physics on the Road” project, which is funded through the American Physical Society Division of Fluid Dynamics.

The Fluid Dynamics Demo Kit is an educational outreach project designing kits that contain experiments to teach students basic fluid and flow concepts. The aim of the project is to use exciting experiments aimed at high school students to teach them practical applications of the concepts they learn in the classroom. These experiments include a water gun, a siphon, Heron’s fountain, and a viscous drag experiment. There is a list of topics covered for each experiment and the assumption is that the topics will have previously been covered in class.

Heron's Fountain

Along with materials for the experiment, each kit includes the information for the teachers and worksheets for the students. There is a PowerPoint presentation which goes along with the experiment, walking through the set-up for the experiment, as well as the procedure, and the calculations that give a basic explanation of all the topics covered. The worksheets are designed to help the high school students walk through the various calculations to get theoretical results, compare them to the experimental results, and explain why they differ. For each experiment a sample worksheet is done with all the calculations written out to provide the teachers with extra guidance.

The supplies needed for each experiment are listed on both the PowerPoint slides and the worksheets. Each kit contains the basic components needed to complete every one of the experiments—beakers, scales, water, and other common laboratory equipment and supplies are assumed to be available to the students and will not be included in the kits. The experiments in all four kits are use parts that are cheap and easy to find, so even if something is broken or lost it can easily be replaced.

In the  water gun experiment, the students choose a target, calculate the number of times they have to pump the water gun, fire the water gun, and then see how close they were to hitting the target. The idea behind the water gun is that by pumping it and adding air, the water in the tank becomes pressurized thus causing it to exit the gun at a faster rate of speed and to go a farther distance. The students have to take measurements of the gun’s performance and calculate in advance the number of times they should have to pump it, using principles including ballistics, conservation of energy, Bernoulli, ideal gas law, conservation of mass, and generation of entropy. Then, using the results from the first test shot, the students calculate the coefficient of friction, recalculate the number of pumps, and fire again hopefully getting closer to the target with friction taken into account.

A siphon is a tube that pumps water up and out of one bucket and down to a bucket at lower lever. Atmospheric pressure is used to pump the water up the tube and then the water flows down into the lower bucket because it has less potential energy. The lab covers principles including Bernoulli, conservation of mass, conservation of energy, and viscous drag. The students are asked to calculate the theoretical time it takes to fill the lower bucket a certain amount and then compare it to experimental results. This lab also then has the students use those results to calculate the frictional losses.

Heron’s fountain, in which water runs up from the bottom tank and out through a tube in the top tank with no pumps, seems impossible. But it is just a matter of pressures pushing the water up and out. To prime the fountain,  water is added to the bottom tank and then the fountain is flipped upside down and water from the bottom tank fills the middle tank pressurizing the middle tank. The high pressure of the middle tank causes the water to flow up and out of the top of the fountain. Over time all the water from the middle tank flows up and out of the top of the fountain and the fountain stops until it is re-primed. The students calculate the time it takes for the fountain to stop running and compare it to the actual time.

The viscous drag experiment involves dropping various size and weight glass spheres in corn syrup and measuring the amount of time it takes for them to fall a certain distance. The students also heat and cool the corn syrup, to see if its viscosity changes at different temperatures. The drag laboratory covers principles including force balance, gravity, viscous drag, and buoyancy.

Our hope is to soon have these four experiments complete, and for the kits ready to be sent out to a few teachers who will test them out and give us feedback. We also hope to add more experiments to the kits, including one that covers surface tension. The education outreach project will help high school students learn to apply fluid concepts to real-world examples, and to gain a deeper understanding and appreciation for theory they learn in lectures.

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