June 5, 2012
How Are Mosquitoes Able To Fly In The Rain?
[ Watch the Video ]
Brett Smith for redOrbit.com
Anyone who has ever seen mosquitoes fly in the rain has probably rooted for the tiny pests to be taken out of the air by the constant barrage of aqua missiles sometimes weighing 50 times their mass.
Unfortunately, mosquitoes have nothing to worry about because their low mass, wing design, hydrophobicity, and hard exoskeleton afford them substantial protection from the rain, according to a new report published in the Proceedings of the National Academy of Sciences.
The Georgia Institute of Technology research team, led by Professor David Hu and his doctoral student Andrew Dickerson, found that mosquitoes receive low impact forces from raindrops because the mass of mosquitoes causes raindrops to lose little momentum as they deflect or pass across the insects.
“The most surprising part of this project was seeing the robustness this small flyer has in the rain,” Dickerson said. “If you were to scale up the impact to human size, we would not survive. It would be like standing in the road and getting hit by a car.”
A video posted by Dickerson also explained that hair on the mosquitoes aids their rain resistance by contributing to their hydrophobicity. The hair accomplishes this by increasing the surface area of the insect´s wings.
In their study, the research team constructed a small acrylic cage covered with mesh to contain six mosquitoes but permit entry of water drops. A water jet was used to simulate rain stream velocity at different speeds. Rain typically travels between 13 and 20 mph as it approaches the ground.
The team found several different types of droplet-insect collisions. A glancing blow would simply rotate the insect in flight; a more direct hit can knock a mosquito down before it quickly recovers. The researchers found another mechanism that allows the mosquito to escape a watery demise.
“To survive, the mosquito must eventually separate from the front of the drop,” Hu said. “The mosquito accomplishes this by using its long legs and wings, whose drag forces act to rotate the mosquito off the point of contact. This is necessary, otherwise the mosquito will be thrown into the ground at the speed of a falling raindrop.”
While the study could have been viewed as an exercise in pest control, the findings also have implications for designers and engineers. The upcoming generation of micro aerial vehicles (MAV) is expected to be the size of bumblebees and could benefit from the study´s findings.
Insect-sized robots are still in the early stages of development, but larger MAVs could also benefit from the findings. One of the smallest robotic flying machines ever was just unveiled by engineers at the University of Illinois. Weighing 1.5 ounces, and having the size of a small bird, the MAV replicates the natural flight of a bird or bat by flapping its wings. An onboard microcontroller even performs the complex mathematical operations necessary for the “craft” to swoop in and perch on a human hand.
No word on if the device, which is being built with a $300,000 grant from the U.S. Air Force, is able to fly through the rain.