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Publications (175)
Three 25 MW downwind offshore rotors with varying chord and twist were designed. • Blade geometry and rotor swept area were considered for maximizing power production. • Empirical correlations were found to estimate flatback airfoil characteristics. • A design space was created to validate prescribed lift coefficient distributions. • Simulations we...
Aeroelastic parked testing of a unique downwind two‐bladed subscale rotor was completed to characterize the response of an extreme‐scale 13‐MW turbine in high‐wind parked conditions. A 20% geometric scaling was used resulting in scaled 20‐m‐long blades, whose structural and stiffness properties were designed using aeroelastic scaling to replicate t...
The increase in popularity of unmanned aerial vehicles (UAVs) has been driven by their use in civilian, education, government, and military applications. However, limited on-board energy storage significantly limits flight time and ultimately usability. The propulsion system plays a critical part in the overall energy consumption of the UAV; theref...
A two-bladed downwind turbine system was upscaled from 13.2 MW to 25 MW by redesigning aerodynamics, structures, and controls. In particular, three 25-MW rotors were developed, and the final version is a fully redesigned model of the original rotor. Despite their radically large sizes, it was found that these 25-MW turbine rotors satisfy this limit...
Offshore extreme-scale turbines of 20–25 MW in size may offer reduced energy costs. The technical barriers at these extreme scales include escalating blade masses with increased flexibility as well as high gravity loads and tower-strike issues. These barriers may be addressed with a load-aligning downwind turbine. To investigate this type of design...
The quest for reduced levelized cost of energy has driven significant growth in wind turbine size; however, larger rotors face significant technical and logistical challenges. The largest published rotor design is 25 MW, and here we consider an even larger 50 MW design with blade length over 250 m. This paper shows that a 50 MW design is indeed pos...
Wind energy is recognized worldwide as cost-effective and environmentally friendly and is among the fastest-growing sources of electrical energy. To further decrease the cost of wind energy, wind turbines are being designed at ever larger scales, which is challenging due to greater structural loads and deflections. Large-scale systems such as moder...
Reduced scale wind turbines can be extremely cost-effective to test new rotor concepts since prototype costs are heavily dependent on the rotor diameter. Ideally, the scaled model would have the same non-dimensional deflections, dynamics, and control behavior as the full-scale model. This would provide a high-fidelity demonstration of the full-scal...
The increase in popularity of unmanned aerial vehicles (UAVs) has been driven by their use in civilian, education, government, and military applications. However, limited on-board energy storage significantly limits flight time and ultimately usability. The propulsion system plays a critical part in the overall energy consumption of the UAV; theref...
The size of offshore wind turbines over the next decade is expected to continually increase due to reduced balance of station costs per MW and also the higher wind energy at increased altitudes that can lead to higher capacity factors. However, there are challenges that may limit the degree of upscaling which is possible. In this paper, a two-blade...
Load alignment, balancing the thrust moment with the centrifugal moment, is a promising innovation for extreme-scale wind turbines. Load alignment allows for longer blades, capturing more power, while maintaining similar blade moments. As blades lengthen, larger coning angles are required to balance increasing thrust moments with centrifugal moment...
We examine the effect of rotor design choices on the power capture and structural loading of each major wind turbine component. A harmonic model for structural loading is derived from simulations using the National Renewable Energy Laboratory (NREL) aeroelastic code FAST to reduce computational expense while evaluating design trade-offs for rotors...
We examine the effect of rotor design choices on the power capture and structural loading of each major wind turbine component. A steady-state, harmonic model derived from simulations using the NREL aeroelastic code FAST is developed to reduce computational expense while evaluating design trade-offs for rotors with radii greater than 100 m. Design...
Novel findings are discussed in this paper that will be especially beneficial to designers and modelers of small-scale unmanned air vehicles and high-altitude long-endurance vehicles that both operate at low Reynolds numbers (Re=50,000–300,000). Propeller-induced flow effects in both tractor and pusher configurations on a rectangular wing using the...
An increase in the number of small quadrotors has created the interest in having performance data on the propellers used by these aircraft. With an aircraft size less than 5 in and propellers diameters less than 3 in, these quadrotors are typically referred to mini, micro, or nano by hobbyists and manufacturers. The size of the propellers used on t...
General Aviation Upset and Stall Aircraft Recovery (GA-USTAR) is a project being conducted by the Applied Aerodynamics Group at the University of Illinois at Urbana-Champaign. GA-USTAR aims to construct a 1/5th dynamically-scaled Cessna 182 model to validate upset and stall flight simulations for general aviation aircraft. Dynamic scaling is the pr...
The thick root airfoils of modern wind turbines, with current technology designs reaching 45% thickness, are incapable of producing high lift, and as a consequence, the blades are aerodynamically and structurally suboptimal. Additionally, the road-transportable blade length is limited to between 53 and 62 m depending on the specific blade geometry....
The Segmented Ultralight Morphing Rotor (SUMR) concept for a 50 MW wind turbine will help alleviate the technical challenges presented by a conventional upwind rotor design for such extreme-scale wind turbines. Such segmented rotor blades can be morphed to achieve load alignment which will significantly reduce the cantilever moments, thus allowing...
A rolling rig for propeller performance testing was developed. The rolling rig presented was used for performance testing of a Mejzlik 27 x 12 TH propeller, which is used on the UIUC AeroTestbed and the UIUC Subscale Sukhoi unmanned research aircraft. The performance parameters measured for the propeller will be used in the future to aid in the cal...
The General Aviation Upset and Stall Testing Aircraft Research (GA-USTAR) project described in this paper aims to develop a dynamically-scaled, Reynolds number corrected, GA aircraft to provide validation data sets for the stall/upset aerodynamic model development. This paper describes the first of three phases of the GA-USTAR project, where the ba...
This paper discusses the motivation, requirements, and approach of the University of Illinois at Urbana-Champaign (UIUC) General Aviation Upset and Stall Testing Aircraft Research (GA-USTAR) project. The goal of the GA-USTAR project is to build and flight test a dynamically-scaled, Reynold number corrected model of a General Aviation (GA) type airc...
Downwind force angles are small for current turbines systems (1–5 MW) such that they may be readily accommodated by conventional upwind configurations. However, analysis indicates that extreme-scale systems (10–20 MW) will have larger angles that may benefit from downwind-aligned configurations. To examine potential rotor mass reduction, the pre-al...
An approach to modeling longitudinal airplane aerodynamics during unsteady maneuvers was developed for a micro air vehicle at angles of attack well past stall under unsteady conditions, including dynamic stall as might be experienced in perching maneuvers. To gather unsteady micro air vehicle flight data, an offboard motion tracking system was used...
A time-marching code for predicting the evolving shape of wind turbine airfoils subject to erosion is discussed. The erosive damage to the blade surface was represented by sand grains colliding with the blade leading edge. The erosion rate was computed on the airfoil, and the damage depth was evaluated at each location. It was found that the locati...
Experimental wind tunnel tests were conducted in the University of Illinois at Urbana-Champaign lowspeed low-turbulence wind tunnel to study the aerodynamics of stalled spinning wings. Wings with airfoils of t=c 10% and aspect ratios between 1 and 10 were tested at pitch angles of 30, 60, and 90 deg. In addition, the effects of airfoil shape were i...
A mathematical model and simulation of airborne particle collisions with a 38 m, 1.5 MW horizontal axis wind turbine blade are presented. Two types of particles were analyzed, namely insects and sand grains. Computations were performed using a two-dimensional inviscid flowfield solver coupled with a particle position code. Three locations along the...
The continuing growth in the use of small UAVs has required the need to more fully understand the propellers that power them. Part of this understanding is the behavior of the propeller slipstream. Using a 7-hole probe, the slipstreams of several small-scale propellers (diameters of 4.2, 5, and 9 in) were measured in both static (V∞ =0 )a nd advanc...
This paper describes initial high angle of attack flight testing performed by a subscale aerobatic aircraft. A 35% scale, 2.6 m (102 in) wingspan Sukhoi 29 S electric aircraft, the UIUC Subscale Sukhoi, was developed and used for this research. The aircraft was instrumented with a custom 100 Hz sensor data acquisition system, which had been previou...
To alleviate the mass-scaling issues associated with conventional upwind rotors of extreme-scale wind turbines (≥10 MW), a morphing downwind-aligned rotor (MoDaR) concept is proposed herein. The concept employs a downwind rotor with blades whose elements are stiff (no intentional flexibility) but with hub-joints that can be unlocked to allow for mo...
A numerical study of how to simulate heavy atmospheric particle collisions with a 38-m, 1.5-MW horizontal axis wind turbine blade is discussed. Two types of particles were considered, namely hailstones and rain drops. Computations were performed by using a two-dimensional inviscid flowfield solver along with a particle position predictor code. Thre...
This paper presents a sensor data acquisition unmanned aerial system (SDAC-UAS) for flight state monitoring and aerodynamic data collection research on small to mid-sized unmanned aerial vehicles (UAVs). The SDAC-UAS was developed to provide the ground-based human (safety) pilot an easily discernible display of sensor and state data for aircraft mo...
An aerodynamic fairing can reduce the effects of the wind turbine tower wake on the blades of a downwind rotor. Previous studies on fairing design have focused on idealized conditions and time-averaged drag reductions, whereas this is the first study to obtain and analyze unsteady velocity field data in the wake of minimum drag fairings at non-zero...
This paper focuses on full six degree-of-freedom aerodynamic modeling of small unmanned aerial vehicles at high angles of attack and high sideslip in maneuvers performed using large control surfaces at large deflections for aircraft with high thrust-to-weight ratios. Configurations, such as this, include many of the currently available propellerdri...
This paper presents results of a study to investigate the effect of leading edge erosion on the aerodynamic performance of a wind turbine airfoil. The tests were conducted on the DU 96-W-180 wind turbine airfoil at three Reynolds numbers between 1 million and 1.85 million, and angles of attack spanning the nominal low drag range of the airfoil. The...
Wind tunnel measurements of rectangular at-plate wings of varying aspect ratios (A = 2, 3, and 4) under different propeller-induced ow conditions were taken at Reynolds numbers from 60,000 to 90,000. The GWS 5×4.3 and GWS 3×3 propellers were used in both the tractor and pusher configurations at various advance ratios. In the tractor configuration,...
A numerical study of how to simulate airborne particle collisions with a 38-m, 1.5-MW horizontal axis wind turbine blade is presented. Two types of particles were analyzed, namely insects and sand grains. Computations were performed using a two-dimensional inviscid flowfield solver coupled with a particle position predictor code. Three locations al...
The growing use of small UAVs and MAVs has increased the interest in determining the performance of small-scale propellers that power them. These small-scale propellers operate at much lower Reynolds numbers than propellers for larger aircraft; typical Reynolds numbers for small-scale propellers are less than 100,000 based on the velocity and chord...
This paper describes a high-frequency sensor data acquisition system (SDAC) for flight control and aerodynamic data collection research on small to mid-sized unmanned aerial vehicles (UAVs). The system is both low weight and low power, operates at 100 Hz and features: a high-frequency, high-resolution six degree-offreedom (6-DOF) inertial measureme...
Unmanned Aerial Vehicles (UAVs) are becoming increasingly popular thanks to an increase in the accessibility of components with high reliability and reduced cost, making them suitable for civil, military and research purposes. Vehicles classified as UAVs can have largely different properties in terms of physical design, size, power, capabilities, a...
High-lift multi-element airfoils, such as those used on large transport aircraft during takeoff and landing, can
generate strong adverse pressure gradients that, while the surface flow is attached, can cause off-the-surface
separation in the wake: so-called wake bursting. The sudden expansion and thickening of the separated wakes has been shown to...
The aerodynamic performance of small-scale fixed-wing flight is not well understood, and flight data is needed to gain a better understanding of the aerodynamics of micro air vehicles. The flight characteristics of micro air vehicles are difficult to measure because the small size and low weight prevent the use of conventional onboard instrumentati...
High lift multielement airfoils, such as those used on large transport aircraft during takeoff and landing,
can generate strong adverse pressure gradients that, while the surface flow is attached, can cause off-thesurface separation in the wake, so called, wake bursting. The sudden expansion and thickening of the separated
wakes has been shown to de...
An aerodynamic shroud was designed to reduce the effects of the wind turbine tower wake on the blades of a downwind rotor. For a given tower diameter and wind speed the shroud was designed to have the minimum drag and minimum chord length downstream of tower centerline, while being able to self-align and resist flow separation when subjected to a n...
This paper describes the development of a large 35%-scale unmanned aerobatic platform named the UIUC Aero Testbed, which is primarily intended to perform aerodynamics research in the full flight regime. The giant-scale aircraft with a 105-in (2.7-m) wingspan and weight of 37 lb (17 kg) was constructed from a commercially available radio control mod...
The effects of configuration changes on the stall/spin characteristics of a single-engine subscale airplane are presented. A 35%-scale, 2.7-m (105-in) wingspan Extra 260 electric aircraft, the UIUC Aero Testbed, was used for this research. A series of flight tests were conduced with the instrumented aircraft, and over 20 different stall/spin maneuv...
This paper presents results of a study that was commissioned by the 3M Re-newable Energy Division to measure the drag reduction by using riblet film on airfoils specifically designed for wind turbine applications. The DU 96-W-180 airfoil was tested with four different symmetrical V-shaped riblet sizes (44, 62, 100 and 150-µm) at three Reynolds numb...
Signficant performance benefits have been found for a wing with a propeller in the tractor configuration at low Reynolds numbers (30,000 to 80,000) based on the wing chord. Propeller induced flow experiments on a wing with an aspect ratio of 4 using the Wortmann FX 63-137 airfoil show that an increase in propeller rotation rate (decreasing advance...
This paper presents results of a study to investigate the impact of using wind protection tape (WPT) to protect the leading edge of wind turbine airfoils from erosion. The tests were conducted on the DU 96-W-180 wind turbine airfoil at three Reynolds numbers between 1 and 1.85 million and angles of attack spanning the low drag range of the airfoil....
Large wind turbines have thick airfoils at the root section of the wind turbine to support the weight of the blade and structural requirements, and aerodynamic efficiencies are in conflict near the root section of the blades. A four-element multielement airfoil system was tested as a replacement airfoil system for a thick single element airfoil nea...
Aerodynamic characteristics of Micro Air Vehicles (MAVs) is not well addressed in aeronautics literature, and more experimental data are required to help better understand the behavior of fixed-wing MAVs. In the current research, aerodynamic characteristics of two MAVs were measured using a motion tracking system. The aircraft used were flat-foam s...
Multielement airfoil configurations have shown promise in improving the aerodynamic characteristics of the inboard section of megawatt-scale wind turbine blades by increasing the lift-to-drag ratios, lift coefficients, and structural efficiency. Steady-state, twodimensional CFD calculations were carried out for a closely-coupled multielement airfoi...
This paper presents wind tunnel results of wings of low-to-moderate aspect ratio (2≤A≤5) at low Reynolds numbers (60,000 to 160,000). Tests were conducted in the low-turbulence wind tunnel in the Subsonic Aerodynamics Research Laboratory at the University of Illinois at Urbana-Champaign (UIUC). A 3-component force/moment balance was designed and fa...
To alleviate the mass-scaling issues associated with conventional upwind rotors of extreme-scale turbines, a downwind rotor concept is proposed which employs fixed blade curvature based on force alignment at rated conditions. For a given peak stress constraint, the reduction in downwind cantilever loads allows reduced shell and spar thickness, and...
The extremely thick blade root airfoils of the modern megawatt-scale wind turbines are prone to having sharp stall characteristics with associated unsteady aerodynamic blade loading and fatigue. With current technology designs reaching 45% thickness, these thick airfoils are incapable of producing high lift, and as a consequence they are aerodynami...
A motion tracking system was used to experimentally determine the aerodynamic forces and moments of two micro UAVs. The airplanes have wingspans ranging from approxi-mately 9 to 15 in and fly at Reynolds numbers below 25,000. The motion track provided a time history of the position and attitude and was used to derive the aerodynamic moments and ana...
This paper investigates the flight mechanics of a micro aerial vehicle without a vertical tail in an effort to reverse-engineer the agility of avian flight. The key to stability and control of such a tailless aircraft lies in the ability to control the incidence angles and dihedral angles of both wings independently. The dihedral angles can be vari...
While much research has been carried out on propellers for full-scale aircraft, not much data exists on propellers applicable to the ever growing number of UAVs. Many of these UAVs use propellers that must operate in the low Reynolds number range of 50,000 to 100,000 based on the propeller chord at the 75% propeller-blade station. Tests were perfor...
This paper describes the wind tunnel testing methodology that has been applied to testing over 200 airfoils at low Reynolds numbers (40,000 to 500,000). The ex-periments were performed in the 2.8×4.0 ft (0.853×1.219 m) low-turbulence wind tunnel in the Subsonic Aerodynamics Research Laboratory at the University of Illi-nois at Urbana-Champaign (UIU...
The behavior of small-scale propellers operating in vertical descent and through the vortex ring state (VRS) was measured. In particular, a total of 26 propellers with diameters ranging from 9 to 11 in. (0.229 to 0.279 m) were tested in the University of Illinois at Urbana-Champaign (UIUC) 2.8×4 ft (0.853×1.219 m) low-turbulence wind tunnel at low...
This paper focuses on full six degree-of-freedom (6-DOF) aerodynamic modeling of small UAVs at high angles of attack and high sideslip in maneuvers performed using large control surfaces at large deflections for aircraft with high thrust-to-weight ratios. Configurations such as this include many of the currently available propellerdriven RC-model a...
This paper focuses on strong propeller effects in a full six degree-of-freedom (6-DOF) aerodynamic modeling of small UAVs at high angles of attack and high sideslip in maneuvers performed using large control surfaces at large deflections for aircraft with high thrust-to-weight ratios. For such configurations, the flight dynamics can be dominated by...
Measuring flight characteristics of micro-UAVs is challenging because of their small size and low weight. These constraints prevent the use of conventional onboard measurement systems. The objective of this research was to capture the state information of a radio controlled (RC) airplane using an off-board motion tracking system and to use this sta...
A morphing segmented concept is proposed herein for future extreme-scale wind turbine systems. The morphing may be accomplished by using segmented blades connected by screw sockets and a tension cable system. At low wind and rotor speeds, the segmented blades are fully tensioned and set at high pitch to ensure start-up and maximum power at low spee...
Dynamic soaring of a sailplane in the Earth's atmospheric boundary layer was computationally investigated over a range of conditions to explore the feasibility of sustained unpowered flight over open fields by taking advantage of wind shear. A point-mass sailplane model was studied, as well as a full six-degree-of-freedom piloted sailplane model. F...
Available performance data for micro propellers are very lacking. Prediction of mi-cro propeller performance is made difficult due to the small Reynolds numbers (less than 50,000) at which the propellers operate. A test rig was designed and built at the Univer-sity of Illinois at Urbana-Champaign in order to measure the static performance of micro...
Limited data exists for propeller and wind turbine post stall aerodynamics. Post stall aerodynamics was observed in small propellers at low Reynolds numbers. First, perfor-mance data (thrust, power, and efficiency) for a set variable pitch propellers was acquired in a wind tunnel. The propellers were 6 to 9.9 inches in diameter and were able to pit...
To reduce the cost of payload to orbit, a conceptual design of a supersonic air-launch system for the Space Exploration Technologies Falcon 1 rocket was performed. Several design candidates were reduced to three preliminary concepts, which in turn underwent comparative analyses to determine a final design that best fulfilled performance requirement...
Copyright: 2006 American Inst of Aeronautics and Astronautics A methodology for the inverse design of non-lifting axisymmetric bodies in compressible flow is presented. In this method, an inverse design approach based on conformal mapping is used to design a set of airfoils in isolation. These airfoils are then assembled into a 3D body and the flow...
an ice management system was designed that would sense and characterize ice, notify the pilot, and if necessary take measures to ensure the safety of the aircraft. The icing simu-lator was used as a platform to integrate and test different components of the Smart Icing System. To create an Icing Encounter Flight Simulator, functionality and Smart I...
Wind Tunnel Aerodynamic Tests of Six Airfoils for Use on Small Wind Turbinesrepresents the fourth installment in a series of volumes documenting the ongoing work of th University of Illinois at Urbana-Champaign Low-Speed Airfoil Tests Program. This particular volume deals with airfoils that are candidates for use on small wind turbines, which opera...
This paper investigates the wake characteristics of rotating and static objects, typical of US Navy ship emitters, using a four-hole Cobra Probe. The Cobra Probe has the ability to measure unsteady 3D velocity. An in-situ calibration was performed and compared to manufacturer specifications. Agreement between the in-situ and manufacturer calibratio...
This paper presents detailed wind tunnel tests data taken on six airfoils having applica-tion to small wind turbines. In particular, lift, drag and moment measurements were taken at Reynolds numbers of 100,000, 200,000, 350,000 and 500,000 for both clean and rough conditions. In some cases, data were also taken at a Reynolds number of 150,000. The...
The centennial of flight has brought about a renewed interest in the first airplanes and their flight characteristics. It is known that the first Wright Flyers were unstable, but history showed that they were flyable. It is the longitudinal handling characteristics that are of interest in this paper. Wind tunnel tests have been performed on the 190...
