Aerodynamics Research Lab
|Faculty Researchers||Lab Location||Phone||Website|
|Phil Ansell (co-director)
Greg Elliott (co-director)
|103 Aerodynamics Research Laboratory||217-244-6918 (lab),
The Aerodynamics Research Laboratory (ARL) houses subsonic wind tunnels utilized to conduct research in aerodynamics, propulsion, and fundamental studies in fluid mechanics. The facility includes advanced instrumentation and flow diagnostics to allow researchers unique insight into the experimental models and flow regimes that are investigated. In recent years, research activities have included studies in unsteady aerodynamics, airfoil icing effects, flow control, motorsports aerodynamics, wind turbine blades, distributed propulsion systems, plasma assisted combustion, and turbojet bypass flows. Much of the performance data of low Reynolds number airfoils (UIUC Airfoil Data Site) and propeller performance curves (UIUC Propeller Data Site) were conducted by Prof. Michael Selig and his students in this facility. ARL has had a wide range of funding sources over the years including, AFOSR, ONR, NASA, DOE, Gulfstream, Rolls-Royce, 3M to name a few.
Facility and Equipment Description
15”x15” Subsonic Wind Tunnel Facility
The 15”x15” wind tunnel at ARL is a fan-driven open-loop design that exhausts outside the laboratory. This tunnel is particularly suited for diagnostic techniques which require particles or when conducting combustion experiments that result in products that need to be exhausted outside the laboratory. The tunnel has a high contraction area ratio resulting and low free stream turbulence and can operate up to a maximum Mach number of 0.4. The 4 foot long test section has excellent optical access for laser diagnostics and utilizes a dedicated 16 channel Netscanner PSI pressure transducer system to monitor total and static pressures of the tunnel and model. This facility has been utilized in the past to study plasma assisted combustion, iced airfoil separation bubbles, flow field from heated stack plumes and other aerodynamic phenomena.
Subsonic Wind Tunnel (2.8 ft x 4 ft)
The 2.8 ft x 4 ft wind tunnel is a low-speed, low-turbulence open-return wind tunnel. The test section features a 2.8-ft height and a 4-ft width, across an 8-ft length. The tunnel is driven by a 150-hp electric motor connected to a 5-bladed fan, and it can be operated at speeds up to a maximum Mach number of 0.2 with a test-section turbulence intensity below 0.1% for all operating conditions. The wind tunnel is operated from a dedicated control room directly adjacent to the wind tunnel high-bay area and is equipped with wide array of instrumentation for experiments. This instrumentation includes an Aerotech 3-component balance, a DTC Initium pressure system with 160 measurement ports, a wake rake composed of 52 total pressure ports, a direct-drive pitching system for unsteady airfoil experiments, and a set of dedicated high-resolution pressure transducers and thermocouples to monitor wind tunnel conditions. These instruments are supplemented by an array of additional capabilities, including advanced diagnostic measurement systems and multi-channel simultaneous sampling systems. This wind tunnel can be utilized to perform experiments across a wide array of test articles, though it is commonly used to conduct aerodynamics experiments on airfoil and wing geometries.
Axisymmetric Inlet/Bypass Transonic Wind Tunnel
The axisymmetric transonic wind tunnel is an in-draft open circuit tunnel with an inner test section diameter and length of 11.1 inches and 9 feet, respectively. It has a contraction ratio of 63:1 and is driven by a 125 hp blower due to the high pressure loss. Axisymmetric models are supported internally to allow the outer walls of the test section to rotate for static wall pressure measurements and radial sting probe measurements using pitot-static probes, hotwires, or 5-hole probes available in the laboratory. This results in a complete mapping of the pressure field on the outer circumference and at complete radial/circumferential cross-sections at any axial location. In addition, discrete surface flow visualization (see below) is utilized in the facility to determine flow direction and regions of flow separation in the channels. The wind tunnel has a maximum local Mach number of 0.6 for the bypass model tested. (Student: Arthur Herrera, Support: Gulfstream Aerospace Corporation and Rolls-Royce Plc.)
Transonic Wind Tunnel
The transonic wind tunnel at the Aerodynamics Research Laboratory is features a 6” × 9” test section and is capable of reaching maximum test-section Mach numbers up to 0.85. This wind tunnel is a continuous, open-return type and is driven by a 250-hp electric motor and centrifugal blower system. The test section is configured with a porous ceiling and floor to mitigate shock reflections and test-section choking. Suction through these porous walls are controlled through a set of motorized flaps that route air through the suction plenum and into the tunnel diffuser. A set of motorized choke vanes are also installed downstream of the test section for fine-tuning of the sonic throat. Ample optical access is provided through a set of optically-clear sidewall windows and a slot in the ceiling for a laser sheet. This wind tunnel is outfitted with a set of dedicated pressure transducers and thermocouples, which are used to monitor and measure tunnel conditions. The wind tunnel utilizes a dedicated 16 channel Netscanner PSI pressure transducer system to measure airfoil pressure distributions. This wind tunnel has been recently used to study innovative transonic natural laminar flow airfoil systems at flight Reynolds numbers for to characterize the drag reduction offered by these airfoils over conventional designs.
Diagnostics and Instrumentation
In addition to housing subsonic and supersonic wind tunnels, the Aerodynamics Research Laboratory is equipped for a wide range of measurement capabilities, ranging from point-based measurement techniques to advanced diagnostic methods. Standard measurement methods include the use of electronically-scanned pressure measurements, 3-component and 6-component integrated force/moment balance systems, thermal anemometry (hot wire and hot film array), multi-hole pressure probe systems, and high-frequency, multi-channel pressure distribution acquisition. Additional instrumentation is also available for high-resolution two- and three-component planar particle image velocimetry, high-speed time-resolved particle image velocimetry, tomographic particle image velocimetry, laser Doppler velocimetry, pressure and temperature sensitive paint measurements, various flow visualization methods, and high-speed photogrammetry. The laboratory also features advanced sampling and data acquisition equipment, including a 48-channel simultaneous sampling system, a 36-channel constant-temperature anemometer system, a 4-axis high-resolution servo controller with motion system. The laboratory is outfitted with a robust sidewall suction system for wall boundary-layer control for testing high-lift airfoil geometries as well as dedicated pneumatic and electrical supply and control systems for active flow control experiments.
Model Assembly/Machine Shop
A model assembly shop is located in room 104 of the Aerodynamics Research Lab. This space provides work benches for instrumenting and constructing models that are tested in the wind tunnels housed in the ARL facility. A variety of hand tools, drill press, manual Bridgeport mill, and 3 axis CNC mill are available to research students to construct and make modifications to their experimental test articles. All students utilizing the tools in the Model Assembly/Machine Shop are trained by university AE shop personnel who also give them a safety check-out. This is an excellent shop to have quick turnaround of minor modifications to a wind tunnel model and give students hands-on experience in machining and manufacturing.
Distributed Propulsion Flight Control Testbed
Ongoing flight testing research at Illinois is currently being conducted in an effort to better understand how aircraft distributed propulsion can be used to enable new control flight capabilities on aircraft platforms. A flight test bed has been developed based on a 21%-scale Cirrus SR22T aircraft, which also includes on-board data acquisition, sensory, and flight computer systems. Flights from this aircraft are used to first develop a dynamics model and understand the baseline aircraft flight performance characteristics. An overwing electric fan distributed propulsion system has also been configured to be integrated into the aircraft to replace the main propulsion system. In addition to providing the necessary thrust to fly this aircraft, the distributed propulsion system is also used to explore the use of system propulsors as control effectors, which can be modulated to perform maneuvers or enable new trim states of the aircraft.
Active Flow Control Flight Research
In order to augment the ground testing research of novel aerodynamic flow control devices, a dedicated UAV-scale aircraft has been developed for integration and flight testing of flow control actuators. Like other efforts, the active flow control testbed uses a 21%-scale Cirrus SR22T aircraft. This aircraft is outfitted with a flight hardware system consisting of an on-board microcontroller, data acquisition unit, and sensor suite. Flight testing research on a new cyclotronic plasma actuator for aerodynamic flow control is currently being performed to indicate the reduction in takeoff and landing distances required with the use of this flow control method.
Spanload Optimization for Minimum Wing Drag
The wake vorticity distribution downstream of an elliptically-loaded wing is shown, with the dominant tip vortex structure displayed. This vorticity distribution was determined from a 5-hole probe survey, which was used to provide a mapping of the velocity distribution across the wake. During this study, a series of optimized wing geometries were developed and experimentally validated in order to better understand the sensitivity of minimum drag on design constraints.
Closed-Loop Aerodynamic Flow Control
Active flow control is commonly envisaged as a way to deliver on-demand control of aerodynamic flows, providing improved performance during critical operational regimes of aircraft. A closed-loop active flow control system was developed to detect, in-situ, the extent of separated flow and the fundamental frequencies of flow instabilities. The system developed in this research effort was able to perform pulsed blowing at this natural frequency of the flow to increase mean actuation effectiveness, with real-time modulation of the blowing amplitude to reach a sufficient to reach a desired value of the airfoil lift.
Airfoil Dynamic Stall Vortex Formation Physics
Dynamic stall is a complex phenomenon in aerodynamics, which occurs for wings and bodies in highly unsteady flow fields. The flow field is dominated by a dynamic stall vortex that forms at the leading edge of an airfoil and leads to drastic increases in flow field unsteadiness and large-amplitude variations in lift, drag, and pitching characteristics. In order to better understand how the dynamic stall process can be better controlled, current research efforts have focused on understanding the detailed formation physics of the dynamic stall vortex itself.
In order to meet future goals in efficiency, a synergistic coupling between aerodynamic surfaces and propulsion systems can be used to reduce energy required for aircraft missions and operational costs. However, little is understood about the coupling between these aerodynamic sections and integrated propulsors. During this study the influence of the propulsion system on the aerodynamic performance of a wing section is studied, as well as the flow field effects that produce these changes.
Laser induced Breakdown Ignition of a Hydrogen Jet in a Crossflow
In order to provide a test case for the next generation of supercomputers (Exascale - 1015 calculations each second) researchers at the University of Illinois are investigating plasma assisted combustion in various turbulent cross flows as a predictive computer simulation target. As part of this effort an experimental target is selected each year to simulate. At ARL researchers are utilizing the 15”x15” tunnel for plasma assisted hydrogen jet ignition from laser induced breakdown (LIB) in a subsonic cross flow as the predictive target. Researchers also utilize a wide array of diagnostics such as particle image velocimetry, coherent anti-stokes Raman spectroscopy, and two photon absorption laser induced fluorescence to characterize the reacting flow field. (Postdoc: Dr. Ryan Fontaine, Support: DOE)
Segmented-Ultralight Morphing Rotor
Research activities conducted by the Applied Aerodynamic Group directed by Prof. Selig at ARL include wind tunnel testing of low Reynolds number airfoils (UIUC Low-Speed Airfoil Testing program), wings, propellers (over 250 propellers tested), and multi-element airfoils. Over 200 low Reynolds number airfoils, many of them new designs, have been built and validated in the UIUC Subsonic Aerodynamics Lab 3x4 ft wind tunnel with the results being documented in books, reports, and journal/conference publications. More recently, for the ARPA-E funded Segmented-Ultralight Morphing Rotor (SUMR) project, wind tunnel tests were conducted to measure power and thrust for subscale highly-coned SUMR wind turbine rotors at various wind speeds and rotation rates. The results obtained here will be used to validate aerodynamics models and simulations carried out by the SUMR team. In addition, airfoils designed for the SUMR turbines will be tested at Reynolds numbers up to 1.5 million at ARL.