# Flow, 2

Previous: Flow

From yesterday... it wasn't that I was thinking of work when I was thinking of "flow", I was at home and being presented with a sensible question that we all knew the answer to intuitively, but logically ran into a wall: how can mosquitoes fly in a car with the windows open?

Intuitively, it's not hard to grasp. They're not going to get pinned to the back windshield when you accelerate because the air in the car is, more or less, moving with the car. It's like: the contents of a jar move with the jar.

But what happens when you open a window? Two windows? Four windows?

At that point in the pile of questions, I could feel old instincts bubble up from the depths. The math behind those instincts—gone. Not completely, maybe, but like athletic activities the impulsive (muscle) memories are still there, even if the capacity is diminished. Also like athletic activities, you learn to distill the things you really need to do to compete from the entire set of things you can do. Can't jump over people in basketball? That's OK. Learn to fake, and then jump around the other players. Can't do all the calculus or finite element analysis anymore? That's OK. Focus on the parts of a problem that you know well, and tune your model for that.

Forget it. This is all a lead up to me drawing pictures to make sense of a problem:

The pictures are trash, but they conjured up long buried memories from differential equations and aerodynamics classes when I could (maybe) draw or code Real Solutions to airflow problems. The Real Solutions are gone. I haven't had to solve a differential equation since I don't know when. (This doesn't diminish the need to learn how to solve those problems. I want engineers that can solve the problems that I have for them, but I also want engineers who learned to survive through training that was harder than what they might see in the field.) But I could feel the intuitive solutions still. I could remember some of the effects of pressure and velocity—static points and choke points and so on.

I could remember, last semester of grad school, taking a boundary layer theory class. And even though it was one of the hardest classes I ever took, I did relatively well in it. Boundary layer theory isn't done—people are still working out why fluids behave the way they do when flows get closer and closer and closer to something that they have to flow over and and around. In that class with sometimes no definitive answers, we could go as far as we wanted to understand the problems we were presented with, and read as much as we wanted to write papers about what we encountered. For someone who likes to revolt against established systems, being asked to learn as much as I wanted was a gift compared to the rest of the classes that focused on scores for this and that rolling up to a composite score that would be compared to the rest of the class for a grade. Grades never interested me much. Picking up a skill or seeing how far I could run in a field was more interesting.

Flow. The physics are easy, and the implementation is hard. Part of me wants to sit down and read more about it—to see what I understand with an older perspective. The majority, though, would like to avoid pain.

Middle age is funny—a sort of recognition of the capabilities that are no more combined with a recognition of the capabilities I can't be bothered to care about—a sort of place where the flow encounters an immovable object and either redirects itself or stops, depending on the math that I am too tired to worry about.