Amateur Aerodynamics

One of the unfortunate realities of cooling system modification and testing is that we can't visually observe what goes on under the hood while the car is driving. Building a physical model of the cooling system may shed some light on what the real system is doing and can be designed for easy observation if you make a window one side of the duct. The air filter here functions the same as a heat exchanger in that it restricts flow and dissipates energy in the form of total pressure loss. Similar to the real cooling system as I decided to analyze it in the previous post, this model has no nozzle outlet. Instead, we have the same as we get in an engine bay: a pressure boundary , meaning an enforced static pressure behind the heat exchanger. Here, that is simply ambient pressure ( C P = 0). While it is not possible to vary atmospheric pressure here, we saw in Part 5 (and will revisit later on) that modifications such as vents can change engine bay static pressure and thus the bound...

In aerodynamics engineering, we talk about pressure a lot . But what is pressure anyway? It's something we're all familiar with in our everyday lived experience: your ears "popping" when you drive up a mountain due to the pressure change with altitude; feeling drained or tired after a long flight in a cabin at a different pressure than what you're used to; sticking your hand out a car window and feeling the "push" of the air backward. You might even remember from a physics or chemistry course that pressure arises from the molecules in a gas zipping around, occasionally bouncing off a surface, and that the faster they move, the greater is the pressure the gas exerts. "Movement" implies velocity alone, but of course the number and mass of these molecules also matters: more mass, greater pressure. Mass and velocity multiplied give momentum , and pressure arises from the transfer of momentum between molecules in a gas and any surface in contact wit...

In my previous spoiler testing, which was extensive, I made a lot of mistakes due to the fact that I only had a little education in engineering. Specifically, there were two major issues that I now want to correct: I did not normalize pressures (that is, turn them into dimensionless values for easier comparison), and I tested at only one Reynolds number. Because of these issues, the results aren’t really generalizable and are not easy to interpret. Let's fix that. Production spoilers are often art as much as—or more than, given how much styling sometimes dictates their shape—functional devices. This Toyota 86 has a very aggressive spoiler design for a production car. Recap   One of my most-read posts here has proven to be an article on spoilers I wrote early on, back when I didn't really know anything yet since I hadn't formally studied aerodynamics. I got the criticism of online theory right (yes, that weird theory that spoilers create "ideal" streamlines—w...