Tuesday, July 9, 2013

Bow waves

The effect didn't videotape very well;
it's actually kind of dark in there.
This plastic sheeting (at left) is giving me an interesting lesson in wind resistance. There’s a remodeling project going on here at work, and the facilities folks kindly put this sheeting up to keep the dust and debris levels down.

When I walk down the hallway, the plastic starts billowing outward — at first, just a half-inch or so right alongside. But as you proceed (at a fairly brisk pace, as I tend to do), the air-compression wave gets stronger and moves ahead of me as far as 15-20 feet. It’s a classic “bow wave” (think of the wave moving ahead of the bow of a boat). 

Yes, if I had to compare my normal bicycling speed to
a watercraft of some sort, it would be this one.
Obviously this is taking place in the relatively confined space of the hallway; still, this has given me a new appreciation for just how much air we’re pushing aside as we ride along on a bicycle and why it gets more and more difficult to maintain a steady pace the faster you go.

I’m compressing and pushing a fairly significant air column out of my way just walking at 3-5 mph.  Imagine what’s happening at 15 or 20 mph, let alone a Tour de France pace.

dsj 130409

1 comment:

  1. I think about air resistance. I think about it a LOT. I bike along a path that follows the shore of Lake Michigan in Chicago. I do this twice a day going to and from work and it's pretty exposed. Whatever the NOAA weather station at Midway Airport (15 miles west) says about wind speed, you can bet it's going to be worse on the Lake Front Path - WAY worse. Add on those bulky panniers and a headwind and you've got a recipe for frustration, and that's just a headwind on top of the normal air resistance. Funny thing is, I feel like my cargo bike overcomes this air resistance better than my touring bike (daily ride). I think there's some sort of inertia thing at work with the cargo bike. Once you get it up to speed it tends to want to stay at that speed for longer than the lighter weight bike. I'm not a physicist, but I'm sure there's some math (hate math), that probably explains all of that.