Having addressed the issue of terminal velocity to death, what if we dropped a bug in a vacuum? Of course, with no wind resistance at all, the landing position would be darned near random, so we’d have the difference between landing on its wings (are we sticking to true bugs here, or using “bug” as a euphomism for any little critter with an exoskeleton?) and landing on its head (or its legs, or…). And what is it landing on?
I don’t think there’s an answer to this unless it gets ridiculously specific.
Bugs don’t have completely central brains. They have structures in the head that deals with learning, visual nerve structures near every eye, and ganglion groups in every segment that deal with muscle control. Two links simple and complex
We all know, from experience with our windshields, that impact at a certain velocity will kill an insect. My experience is that you don’t get much bug splat until you exceed 60 miles per hour. I’m not sure if it’s because slower impacts don’t kill, or because at slower speeds bugs can get the hell out of the way. But, for the sake of argument, let’s say 60 mph, or 88 feet per second, is the magic speed.
Acceleration due to Earth surface gravity = 32 feet/sec/sec, so a bug in a vacuum will accelerate to 88 feet per second in 2.75 seconds, during which time it will fall 121 feet.
Testing, anyone? Does anyone have access to a vertical, 120-foot-long vacuum tube?
NASA Lewis Research Center (aka Glenn Research Center, but I think it’s silly to rename it now) in Cleveland has a vacuum chamber 133 meters tall, and it’s specifically designed to drop things down it. Center employees jokingly refer to it as the “Martha Washington Monument”, because it’s a hole in the ground the same height as the Washington Monument obelisk. Unfortunately, it doesn’t appear that anyone calls it that on a webpage…
What are the chances that NGRC is willing to expand from microgravity combustion experiments to bug impact studies?
Although I would imagine that a windshield/radiator grill is a fairly effective means of gauging the velocity to splat different bugs (although some may be too small for their momentum to overcome aerodynamic forces)
The important issue here is how well the bug tracks the air flow. At moderate speed, it’s unlikely the bugs are getting out of their way under their own power, but they are being swept out of the way by the air that’s being pushed aside by the car. At higher speeds, the air can’t accelerate them fast enough to get them out of the way. They lag the air movement and get hit by the vehicle. The car’s velocity is an issue, but it also depends on the mass and drag coefficient of the bug. Some bugs surf, some splat.
How well a particle (bug) tracks the flow is a very well-studied problem in fluid dynamics because particles are often injected in wind tunnels for flow visualization and diagnostics. Bigger particles give better visibility, but too much mass means the particle won’t track the flow around obstacles. From my work in flow vis, this is more art than science, but it is possible to analyze the momentum and drag of the particle (bug) to see if it will follow the flow around an obstacle or go its own way (splat).
Yeah, I’ve noticed that. It fascinates me. It seems like, driving in the 60’s (mph), you get more skaters, but as you accelerate into the 70’s, you get more splatters. But you never get all one or all the other, reinforcing your point that bug airfoil plays a role in addition to velocity.
My gut feeling (heh heh) is that impacts slower than 60 mph would be just as fatal, but they don’t happen very often because of the air flow factor that you describe. Only vaccum tube experimentation can resolve this.
I hadn’t looked at it in the right context before, but both my PhD. research (in a supersonic wind tunnel) and my post-doc work (in laminar water channel) could be interpreted as spot-on this issue. I find that somehow unsettling.
Well, I just got out of the wind tunnel an hour ago where we were seeding the flow. Unfortunately, the particle size we were using was significantly smaller than most bugs. In fact, we were commenting on how the people who make the seeding material were crazy to think you would actually get particles as big as 50 microns in a real experiment. Maybe I can convince them to see with gnats and get back to you.
Note that there’s a big difference between not tracking the flow and not tracking the flow so badly you impinge on the flow obstruction. The bugs aren’t necessarily tracking the flow well compared to the particles we use for flow vis and laser diagnostics, but they may still avoid the splat.
