Research Interests in Applied Aerodynamics
Applied aerodynamics is the art and science of taking what we understand about the fundamentals of fluid flow and applying that to make a better aerodynamic system. Sometimes the process begins by researching the basic underlying fluid dynamics of the flow around some object, e.g. airfoil stall or rotors in steep descent. Other times when the fluid dynamics are better understood, it focuses on using aerodynamics tools and "know-how" in the process of advancing and optimizing the design of a system, e.g. designing a new airfoil to optimize a system like a new airplane, UAV or wind turbine.
Applied aerodynamics covers a broad range of topics involving generally any object that experiences aerodynamic forces in fluid flow, e.g. aircraft, wind turbines, yachts, automobiles/race cars, trains, sports balls, birds and insects to name a few. Currently, most of our particular research interests tend to center around and have impact on the following areas below.
Airfoil Design and Validation
Unique airfoil requirements and interests in improving aerodynamic efficiency are drivers on our research into airfoil design and validation. Methods at UIUC build off of an inverse design approach whereby the desired aerodynamic characteristics are specified from which the geometry is determined. At the heart of the approach is the inverse design code PROFOIL, which has been used to design single-element airfoils, multi-element airfoils, airfoils in cascade and airfoil in distributions along wings, i.e. 3D methods. The suite of 2D and 3D flow codes developed and built around the core PROFOIL engine have been applied in the design of airfoils and wings that are in use worldwide for a range of military and civilian applications. Some examples are airfoils for model aircraft, UAVs, homebuilt aircraft, large and small wind turbines as well as designs used in the America's Cup and Formula 1 racing series. New designs are validated using CFD methods and wind tunnel testing at UIUC. Some sponsors of our research have included NASA, AeroVironment, Boeing, Naval Research Lab, GE, Siemens, Northern Power Systems, Ford Motorsports, NHR, Jaguar Racing and Oracle-BMW Racing, Farr Yacht Design and many others.
Low Reynolds Number Aerodynamics of Airfoils, Propellers and Vehicles
Model aircraft, MAVs/UAVs, cooling fans and many other systems operating at small scale and low speeds can experience low Reynolds number flow effects. Low Reynolds numbers are also experienced on aircraft with low wing loadings flying at very high altitudes, such as 40,000 ft and above. If the aerodynamics are not managed well, the performance of such systems can seriously degrade and become economically and technically infeasible. For a conventionally shaped airfoil, these problems can occur when the Reynolds number falls below approximately 500,000. Low Reynolds number aerodynamics has been one focal point of our research in the UIUC Applied Aerodynamics Group. We have designed and tested new airfoils that are used in aerospace, wind energy, motorsports and sailing. Some examples include airfoil designs for the NASA/AeroVironment solar powered aircraft (e.g. 247-ft span flying-wing Centurion and Helios), AeroVironment Global Observer, UAVs, many model aircraft as well as airfoils for the wing-keel bulbs in the America's Cup and aerodynamic wings used in CART and Formula 1 designs. Research into the aerodynamics of low Reynolds number propellers is also ongoing. Over 100 propellers have been wind tunnel tested in straight flight, yawed flow and in steep descent. Also, full-vehicle low Reynolds number aerodynamics of UAVs is an area of research in our group. For more see UIUC LSATs.
Wind Turbine Blade Design and Wind Energy Research
Wind energy is growing at an unprecedented rate. Our research in this area centers around airfoil designs for wind turbine blades as well as the aerodynamic design of the entire rotor. We have used PROFOIL for wind turbine airfoil design and PROPID for inverse design of variable-speed and constant-speed rotor blades. One variant, PROPGA, is a hybrid approach that combines the advantages of an inverse design method with the optimization power of a genetic algorithm. These methods include approaches to capture high angle of attack post-stall aerodynamics. Areas of current research range from blade design with very thick airfoils for mega-watt scale large wind turbines to the airfoil and blade design for low Reynolds number small rotor systems. Applications of these methods include the large ~70-m dia 1.5-MW GE wind turbine (see patents) as well as many medium- and small-size rotor systems for companies and for government sponsored research. Research into 3D stall delay continues to be a challenging and interesting area of study. For more see the PROPID webpage.
Realtime Flight Simulation and Computational Flight Dynamics
Our research in realtime flight simulation of aircraft covers a broad spectrum. Over 30 small-scale UAV-sized aircraft (RC aircraft in fact) have been modeled in the flight simulation software FS One, which is now being used on campus in our research. Flight vehicles as small as 3 grams ("nano" MAVs) up to full-scale size are modeled in realtime at 300 Hz using a 4th-order Runge-Kutta integration scheme. The aerodynamics methods embodied in the base-code include a spectrum of nonlinear low Reynolds number effects and high angle of attack post-stall aerodynamics which give rise to a range of interesting topics for research such as the aerodynamics of airplane hover, unsteady lift and drag modeling in dynamic maneuvers, and incipient and fully-developed aircraft spin. Research in flight simulation at UIUC has also included realtime modeling of the early IAI Pioneer UAV, the NASA Twin Otter icing research aircraft, and the University of Toronto full-scale ornithopter to name a few. One of our current efforts in flight simulation and modeling is aimed at aircraft dynamics and control for energy extraction from wind shear and random gusts, e.g. dynamic soaring. Our work in flight simulation and modeling research has also been applied to aircraft accidents. Experience has also been applied to better understand aircraft loss of control in one of the worst aviation accidents in US history.