Bats are unique animals, and present a very compelling model for small scale animal flight. The following characteristics of bats and their accomplishment of flight are particularly interesting for inspiring developments in unmanned aerial vehicle design:
Bats are extremely manouverable animals, often capable of rapid changes in direction (prey capture, manouvering, capture evasion, etc). This maneuverability is desireable for unmanned vehicles providing the potential for perching, and flight through urban-like environments.
Bats are efficient and effective flapping flight vehicles. A primary concern of unmanned aerial vehicles is gaining an efficient low power platform.
Bats utilize an actuated morphing membrane wing structure to achieve flight. The active membrane used by bats presents an attractive strategy for UAV flight where membranes would be simpler to design, build and fly than feathered wings. Membrane wings may also provide aerodynamic advantages such as camber inducing, stall alleviation, and softer stall.
In this project we are examining the aero-structural characteristics of bat flight to determine the applicability of similar structural strategies in vehicle design.
Our collaborators at Brown University (Breuer Lab and Swartz Lab) provide state of the art high speed stereo digital video capture of bats in flight (both in windtunnels and flight cages). This video data is processed using state of the art motion capture approaches. Following motion capture a 3-dimensional reconstruction and surface model of the bats are constructed. These high fidelity, time accurate models of bat flight provide an accurate shape which can be analysed using computational methods.
Using several different computational tools, we are examining the flight and efficiency of flight. The computational tools which are considered are HallOpt, ASWING, FastAero, and 3DG. Each of these tools is briefly highlighted below (See the tools page for details):
- HallOpt: Using the trace of the trailing edge line we can construct and approximate wake sheet. Using methods proposed by Hall et al., we examine these wakes to determine how vorticity should be distributed in the wake of a bat if the lift and thrust generation is performed in an efficient manner.
- ASWING: Using simple, yet accurate, models for aerodynamics, structures and dynamics, simulating the flight of a bat or flapping vehicle is simple.
- FastAero: Using a potential flow model, and the 3-dimensional bat geometry, the flow around the bat can be simulated rapidly using an accelerated potential flow method. FastAero, originally designed for aircraft analysis applications has proven useful where a tradoff between time and flow physics accuracy is desireable.
- 3DG: 3DG is a discontinuous Galerkin method for solving the Navier Stokes equations. This method is very accurate; however, can be time consuming to use for large 3-dimensional simulations. As such, the method is used for confirming results and roviding insight into viscous effects.
Please explore the links to the Right Hand Side to learn more about the project.
The current project has been funded by several different sources at different times. We are very thankful to the following funding sources:
Singapore-MIT Alliance (SMA), National Science Foundation (NSF), Natural Science and Engineering Councile of Canada (NSERC), and the Air Force Office of Scientific Research.