# Summer Career Connections at SAVY 2018: Session 4, Day 3 – Engineering Design (Rising 7th)

Posted by on Wednesday, July 11, 2018 in SAVY, Uncategorized.

This morning we finished our first designs! It was a real challenge learning how to use a CAD program and how to design for laser cutting, but we pulled through and designed some really good gliders. These parts will be laser cut tonight so we can test tomorrow.

In preparation for our testing, we learned all about how real engineers test things this afternoon. We wanted to start with the basics of numerical modeling techniques, so we started with learning about discretization. Discretization is taking a continuous model or equation and breaking it into tiny discrete parts. We demonstrated this by trying to draw a circle with only a few straight lines. The students decided that your discretized functions are more accurate when you break it into more parts (or have a smaller step size). Either way, numerical techniques always have error. You can’t eliminate it. You can only reduce it.

To continue with our modeling and simulation, we then learned about commercial modeling techniques. Commercial modeling techniques do all the numerical modeling for us, but they’re not infallible. Models are only as good as the information you give it, or as we say “garbage in, garbage out.”

After spending some time on the computer simulation side of things, we switched over to talking about how engineers physically test thing. How can engineers test small models and how do they know the results are valid? For aerodynamics, they do it by matching non-dimensional parameters. By matching Reynolds numbers (our non-dimensional parameter of choice for airplanes), we created multiple potential experiments for a single real life condition. Ask your students if a honey tunnel is a practical alternative to a wind tunnel!

Finally, we spent some time talking about what I do as a mechanical engineer. Since I work a lot on materials and metals, I use the design cycle differently than someone who designs planes or cars. The students even got to pass around a piece of meteorite that I use in my research.

Tomorrow we’ll test!

-Kelsay