The NY Times published an article on insect aerodynamics last week (and also a beautiful photo series featuring recent science photos).
I've been immersed in micro-hydraulics for a few weeks now. Our Emriver models work in this realm of centimeter-deep flows and low Reynolds numbers. I've been going through the literature trying to make sense of it. No small feat; authors can't even agree on basic things, and most of the work's in engineering, with severely restricted experiments, not freely meandering channels like the ones we use. I keep going back to Steven Vogel's wonderful book Life in Moving Fluids. Vogel explains these things much better than the engineers who write about hydraulic modeling do.
The Times article scientists used a combination of mathematical models and tethered insets in wind tunnels. While there is much work to be done on the use of low density plastic media in river models, I argue that the mathematical models are not any better at prediction. Which is one of the reasons we keep building the physical ones. And because they're a lot more fun.
From the Times article:
The researchers suggest there is a lesson in this for engineers who are trying to develop tiny flying vehicles that mimic insects. Camber and the ability to twist while flapping are the keys to success, they say. But insects are far advanced when it comes to wing materials that can flap and twist thousands of times without cracking or tearing. The researchers note in the paper that it may be difficult for engineers “even to approach the elegance of an insect.”I'd argue the workings of an alluvial river are certainly as complex as an insects wings, and we have a long way to go in our understanding, and need all the tools we can find.
Photo from the article in Science.