Инженерная теория против бытовой практики: как попытка оптимизации полива привела к провалу системы

A friend from my old hackerspace was in grad school for electrical engineering. He had a professor who would ask, when something went wrong with a student project, “Have you fully characterized the system?” It’s a good, if lofty, goal, but it also became an inside joke around the hackerspace because YOLO was our MO about 95% of the time. Head crashes on the 3D printer – “not fully characterized”. Forgot to take out the trash last weekend? Was the system fully characterized? It’s maybe also the difference between theory and practice: In theory, there’s no difference between theory and practice, and all systems can be fully characterized. But in practice, it’s hard to fully characterize a system that you don’t yet fully understand. Case in point: we have nine small saplings growing in our front yard, and I have to water them. It’s boring moving the hose from tree to tree, so I thought I’d take a length of hose, stopper it at one end, and drill enough holes in it so that it could irrigate all of the trees at once. I kinda characterized the system: I figured out how much water flows per minute through our hose, and divided that up into a reasonable outflow in my mind, and drilled holes that ended up being way too large. Why? Because a length of hose has a resistance to flow, and the water came pouring out of the first few holes, while the last few were dry. It wasn’t a constant pressure system like I thought it would be. I hadn’t even thought that the drag in the hose would matter, so there was no way I would have tried to measure it. But how would I characterize this resistance anyway? You could make a hose with too-large holes and measure the falloff. (Oops, that’s exactly what I did.) In retrospect, professional drip irrigation systems always have holes that are tiny relative to the pipe diameter, which avoids this pressure-drop phenomenon, which means that they don’t have to worry about characterizing the hose resistance. So that’s what I ended up doing. I cut the hole size in half, and later widened up some of the downstream holes until it looked about right. Not even close to fully characterized, but it works. So now, in addition to the engineer’s “have you fully characterized the system?”, I have the hacker’s “can you avoid characterizing parts of the system?” in my mind. And a holey chunk of hose in the trashcan. Supercon News Just briefly, in case you missed it: Tickets are on sale now for Supercon Ten, and we’ve extended the call for participation by another two weeks. If you’re a Hackaday fan, you owe it to yourself to join us at our annual gathering.