Water Tunnel is Used to Study Flapping Flight

With the approaching completion of the latest flapping mechanism, Steve Naegle is focusing his efforts on preparing for flapping experiments. The flapping mechanism will be studied underwater so that the wings can be flapped more slowly than in air.
Primarily used by the civil engineering department to simulate flows in riverbeds and around bridges, the water tunnel to be used is the only one on campus that is large enough to provide a consistent flow around the wings of the flapping mechanism. Size is important so that the wingtips do not enter the boundary layers near the walls of the tunnel. “The water tunnel is huge,” says Naegle. “It’s a lot bigger than what I was expecting the first time I saw it.”
Naegle will be using a technique called Particle Image Velocimetry (PIV) to get information about the flow of the water around the flapping wings. PIV works by seeding the water flow with small particles and taking pictures of them as they move past the wings. By tracking how each particle moves from one image to the next, the velocity of the fluid can be determined.
“With information about the fluid velocity we can estimate the lift and forward thrust generated by the wings,” says Naegle. “We are trying to understand why certain flapping motions are more effective than others, and using PIV to visualize the flow pattern will help us describe what is going on behind the wings.”
Experimentation will begin in the water tunnel when the manufacturing of the mechanism is completed.