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13th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference, MAO 2010

作者： Crahan, Grady Rennie, Mark Jumper, Eric J. Tovar, Andrés Mejía-Rodríguez, Gilberto Renaud, John E. Center for Flow Physics and Control Department of Aerospace and Mechanical Engineering University of Notre Dame Notre Dame IN 46556 United States Design Automation Laboratory Department of Aerospace and Mechanical Engineering University of Notre Dame Notre Dame IN 46556 United States

ISBN: (纸本)9781600869549

Aero-optic aberrations originating from the nearby flowfield of an aircraft can seriously limit the ability to focus on-board laser systems onto farfield targets. These aero-optic aberrations can be mitigated by using fences to control the flow around the outgoing beam aperture. The objective of this investigation is to attempt to determine the best shape for these fences using computational fluid dynamics in combination with optimization techniques. Future work will experimentally and computationally build on the solutions presented here. © 2010 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Fences

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Non-intrusive measurements of a four-bladed rotor in hover - A first look

Non-intrusive measurements of a four-bladed rotor in hover -...

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AHS Aeromechanics Specialists Conference 2010

作者： Wong, Oliver D. Noonan, Kevin W. Watkins, A. Neal Jenkins, Luther N. Yao, Chung-Sheng U.S. Army Aeroflightdynamics Directorate NASA Langley Research Center Hampton VA 23681 United States Advanced Sensing and Optical Measurement Branch NASA Langley Research Center Hampton VA 23681 United States Flow Physics and Control Branch NASA Langley Research Center Hampton VA 23681 United States

ISBN: (纸本)9781615679898

A hover test using non-intrusive measurement techniques was conducted on a model scale four-bladed rotor in the NASA Langley 14- by 22- foot tunnel rotor test cell. Tests were conducted at thrust coefficients of 0.005, 0.007 and 0.009 to validate pressure sensitive paint (PSP) measurements on the rotor blade tips and to utilize a large field of view stereoscopic particle image velocimetry (PIV) system. Rotor forces and control settings were also measured and are presented here. Comparison of the PSP and conventional pressure tap measurements show reasonable correlation for most conditions and excellent correlation at the higher thrust conditions. The measurement plane of the PIV system was large enough, 5.0 feet high x 3.0 feet wide, to simultaneously capture the vortices from three blade passages. Rotor wake data is presented. Lessons learned and future directions are discussed.

关键词： NASA

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Feedforward adaptive-optic correction of a compressible shear layer using a laser beacon

Feedforward adaptive-optic correction of a compressible shea...

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作者： Rennie, R. Mark Goorskey, David Whiteley, Matthew R. Cavalieri, David Jumper, Eric J. Center for Flow Physics and Control University of Notre Dame Notre Dame IN 46556 United States MZA Associates Corporation Dayton OH 45459 United States Department of Aerospace and Mechanical Engineering United States MZA Dayton Operations United States

ISBN: (纸本)9781600867453

A feedforward adaptive-optic correction approach was investigated in which the return light from an artificial guide star is used to synchronize the deformable mirror with the regularized aberrations of a forced compressible shear layer with high- and low-speed Mach numbers of 0.75 and 0.12. The guide star was created by focusing a pulsed, frequency-tripled Nd:YAG laser emitting in the ultraviolet to create a laser-induced air breakdown spark. The experiments showed that the beacon system could successfully synchronize the feedforward correction to within a few hundredths of a millisecond, and that this temporal error would introduce a residual OPDrms on the corrected wavefront of around 0.06 μm. © 2010 by Rennie, R.M., Goorskey, D., Whiteley, M.R., Cavalieri, D., & Jumper, E.J.

关键词： Yttrium aluminum garnet

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Orbiter boundary layer transition prediction tool enhancements

Orbiter boundary layer transition prediction tool enhancemen...

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作者： Berry, Scott A. King, Rudolph A. Kegerise, Michael A. Wood, William A. Anderson, Brian P. NASA Langley Research Center Aerothermodynamics Branch MS 408A Hampton VA 23681 United States NASA Langley Research Center Flow Physics and Control Branch MS 170 Hampton VA 23681 United States Applied Aeroscience and CFD Branch NASA Johnson Space Center M/S EG3 Houston TX United States

ISBN: (纸本)9781600867392

Updates to an analytic tool developed for Shuttle support to predict the onset of boundary layer transition resulting from thermal protection system damage or repair are presented. The boundary layer transition tool is part of a suite of tools that analyze the local aerothermodynamic environment to enable informed disposition of damage for making recommendations to fly as is or to repair. Using mission specific trajectory information and details of each damage site or repair, the expected time (and thus Mach number) of transition onset is predicted to help define proper environments for use in subsequent thermal and stress analysis of the thermal protection system and structure. The boundary layer transition criteria utilized within the tool were updated based on new local boundary layer properties obtained from high fidelity computational solutions. Also, new ground-based measurements were obtained to allow for a wider parametric variation with both protuberances and cavities and then the resulting correlations were calibrated against updated flight data. The end result is to provide correlations that allow increased confidence with the resulting transition predictions. Recently, a new approach was adopted to remove conservatism in terms of sustained turbulence along the wing leading edge. Finally, some of the newer flight data are also discussed in terms of how these results reflect back on the updated correlations.

关键词： Stress analysis

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NASA high-reynolds number circulation control research - Overview of CFD and planned experiments

NASA high-reynolds number circulation control research - Ove...

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作者： Milholen II, W.E. Jones, G.S. Cagle, C.M. NASA Langley Research Center Configuration Aerodynamics Branch MS 499 Hampton VA 23681-2199 United States NASA Langley Research Center Flow Physics and Control Branch MS 499 Hampton VA 23681-2199 United States NASA Langley Research Center Aeronautics Systems Engineering Branch MS 238 Hampton VA 23681-2199 United States

ISBN: (纸本)9781600867392

A new capability to test active flow control concepts and propulsion simulations at high Reynolds numbers in the National Transonic Facility at the NASA Langley Research center is being developed. This technique is focused on the use of semi-span models due to their increased model size and relative ease of routing high-pressure air to the model. A new dual flow-path high-pressure air delivery station has been designed, along with a new high performance transonic semi-span wing model. The modular wind tunnel model is designed for testing circulation control concepts at both transonic cruise and low-speed high-lift conditions. The ability of the model to test other active flow control techniques will be highlighted. In addition, a new higher capacity semi-span force and moment wind tunnel balance has been completed and calibrated to enable testing at transonic conditions.

关键词： NASA

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Laminar-turbulent transition behind discrete roughness elements in a high-speed boundary layer

Laminar-turbulent transition behind discrete roughness eleme...

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作者： Choudhari, Meelan Li, Fei Wu, Minwei Chang, Chau-Lyan Edwards, Jack Kegerise, Michael King, Rudolph Computational AeroSciences Branch NASA Langley Research Center M.S. 128 Hampton VA 23681 United States National Institute of Aerospace Hampton VA United States Department of Mechanical and Aerospace Engineering North Carolina State University Raleigh NC 27695 United States Flow Physics and Control Branch NASA Langley Research Center M.S. 170 Hampton VA 23681 United States

ISBN: (纸本)9781600867392

Computations are performed to study the flow past an isolated roughness element in a Mach 3.5, laminar, flat plate boundary layer. To determine the effects of the roughness element on the location of laminar-turbulent transition inside the boundary layer, the instability characteristics of the stationary wake behind the roughness element are investigated over a range of roughness heights. The wake flow adjacent to the spanwise plane of symmetry is characterized by a narrow region of increased boundary layer thickness. Beyond the near wake region, the centerline streak is surrounded by a pair of high-speed streaks with reduced boundary layer thickness and a secondary, outer pair of lower-speed streaks. Similar to the spanwise periodic pattern of streaks behind an array of regularly spaced roughness elements, the above wake structure persists over large distances and can sustain strong enough convective instabilities to cause an earlier onset of transition when the roughness height is sufficiently large. Time accurate computations are performed to clarify additional issues such as the role of the nearfield of the roughness element during the generation of streak instabilities, as well as to reveal selected details of their nonlinear evolution. Effects of roughness element shape on the streak amplitudes and the interactions between multiple roughness elements aligned along the flow direction are also investigated.

关键词： Wakes

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Designing and testing a high-bandwidth 2-D wavefront sensor for aero-optics

Designing and testing a high-bandwidth 2-D wavefront sensor ...

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SPIE Optical Engineering + Applications

作者： Abado, Shaddy Gordeyev, Stanislav Jumper, Eric J. Center for Flow Physics and Control University of Notre Dame Notre Dame IN 46656 United States

ISBN: (纸本)9780819477569

A novel two-dimensional high-bandwidth Shack-Hartmann wavefront sensor was designed, addressing the high temporal bandwidth of optical aberrations caused by compressible flows. The principle of operation and modifications from an earlier version of the wavefront sensor are presented and compared to a commercially available wavefront sensor. A wavefront reconstruction algorithm is derived. The high-temporal resolution and spatial resolution of the sensor is demonstrated. A two-dimensional, acoustically forced heated jet was used to test the sensor. © 2009 SPIE.

关键词： Adaptive optics

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Stability of supersonic boundary layers on a cone at an angle of attack

Stability of supersonic boundary layers on a cone at an angl...

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作者： Balakumar, P. Flow Physics and Control Branch NASA Langley Research Center Hampton VA 23681 United States

ISBN: (纸本)9781563479755

The stability and receptivity of three-dimensional supersonic boundary layers over a 7° sharp tipped straight cone at an angle of attack of 4.2° is numerically investigated at a free stream Mach number of 3.5 and at two high Reynolds numbers, 0.25 and 0.50*106/inch. The generation and evolution of stationary crossflow vortices are also investigated by performing simulations with three-dimensional roughness elements located on the surface of the cone. The flow fields with and without the roughness elements are obtained by solving the full Navier-Stokes equations in cylindrical coordinates using the fifth-order accurate weighted essentially non-oscillatory (WENO) scheme for spatial discretization and using the third-order total-variation-diminishing (TVD) Runge-Kutta scheme for temporal integration. Stability computations reveal that the azimuthal wavenumbers are in the range of m ∼ 25-50 for the most amplified traveling disturbances and in the range of m ∼ 40-70 for the stationary disturbances. The N-Factor computations predicted that transition would occur further forward in the middle of the cone compared to the transition fronts near the windward and the leeward planes. The simulations revealed that the crossflow vortices originating from the nose region propagate towards the leeward plane. No perturbations were observed in the lower part of the cone.

关键词： Angle of attack

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Wake measurement downstream of a hybrid wing body model with blown flaps

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International Journal of flow control 2010年第1期2卷 1-19页

作者： Lin, John Jones, Gregory Allan, Brian Westra, Bryan Collins, Scott Zeune, Cale NASA Langley Research Center Hampton VI 23681 United States Northrop Grumman Corporation El Segundo CA 90245 United States Air Force Research Laboratory Wright-Patterson AFB OH 45433 United States Flow Physics and Control Branch MS 170 United States Propulsion System Design and Integration MS 9V14/W6 United States Future Tactical Systems MS XE 40/W6 United States AFRL/RBAA United States

flow-field measurements were obtained in the wake of a full-span Hybrid Wing Body model featuring steady blowing through internally blown flaps. The test was performed at the NASA Langley 14×22 Foot Subsonic Tunnel at low speeds. Off-body measurements were obtained with a 7-hole probe rake survey system. Three model configurations were investigated. At 0° angle of attack the surveys were completed with 0° and 60° flap deflections. At 10° angle of attack the wake surveys were completed with a slat and a 60° flap deflection. The 7-hole probe results further quantified two known swirling regions (downstream of the outboard flap edge and the inboard/outboard flap juncture) for the 60° flap cases with blowing at both angles of attack. flow-field results and the general trends are very similar for the two blowing cases at nozzle pressure ratios of 1.37 and 1.56. High downwash velocities correlated with the enhanced lift for the 60° flap cases with blowing. Jet-induced effects are the largest at the most inboard station for all (three) velocity components due in part to the larger inboard slot height. The experimental data are being used for the validation of computational tools for high-lift wings with integrated powered-lift technologies.

关键词： Angle of attack

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flow separation control on trailing edge radii using single dielectric barrier discharge plasma actuators: An application to vehicle drag control

Flow separation control on trailing edge radii using single ...

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The Aerodynamics of Heavy Vehicles II: Trucks, Buses, and Trains

作者： Spivey, R. Hewitt, R. Othman, H. Corke, T. Mach Zero Associates United States Center for Flow Physics Control Aerospace and Mechanical Engineering Department University of Notre Dame United States

As cruise speeds of ground vehicles has risen to as high as 70 miles per hour, overcoming the aerodynamic drag has become a significant percentage of the total power required. Engines have been increased in power and fuel tanks made larger to provide reasonable range between fuel stops. Heavy truck data in particular indicate that 2/3rds of the cruise power is needed to overcome drag. This paper focuses on reducing drag on class-8 trucks, but the principles can be applied to lighter trucks, busses, pick-ups, SUVs, and many other ground vehicles. The University of Notre Dame has developed unique actuators that have shown potential to maintain unseparated airflow around corners. This technology promises to reduce drag on ground vehicles thus increase fuel efficiency and gas mileage. This paper discusses these actuators and the preliminary wind tunnel tests that have been conducted at Notre Dame in 2007. The cost of fuel has risen so rapidly in the past few years that drag is now a major contributor to the cost of moving freight and consumer goods around the country. The use of these actuators can be applied to passenger cars and as well as many other types of ground vehicles. © 2009 Springer-Verlag Berlin Heidelberg.

关键词： Actuators

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