Academic literature on the topic 'Wake Flight Testing'
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Journal articles on the topic "Wake Flight Testing"
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Zawodny, Nikolas, Nicole Pettingill, and Christopher Thurman. "Identification and Reduction of Interactional Noise of a Quadcopter in Hover and Forward Flight Conditions." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 265, no. 5 (February 1, 2023): 2947–58. http://dx.doi.org/10.3397/in_2022_0415.
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Advanced Air Mobility is a vision for a safe, accessible, and sustainable aviation system to transport people and packages between places not served by traditional aviation. With this emerging transportation industry, there is motivation to characterize the noise of vehicles to determine their potential impacts on the community. An experimental testing campaign was conducted on a small unmanned aerial vehicle in the NASA Langley Low Speed Aeroacoustic Wind Tunnel as a continuation of a previous testing campaign. The goals of the current test are to identify sources of interactional noise as well as to test custom designed rotors and noise reduction devices. The tested noise reduction methods involve increasing the vertical distances between the rotors and the vehicle airframe as well as between the forward and aft rotor disk planes. These methods are intended to reduce rotor-airframe interaction noise in hover and fore-aft rotor wake ingestion noise in forward flight. A phased microphone array is also utilized to identify the locations of prominent noise generation for the different vehicle configurations in forward flight. Elevation of the rotors from the vehicle airframe yielded up to an 8 dBA noise reduction in forward flight, while yielding only modest noise reductions in hover.
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Zhelannikov, A. I. "Features of vortex trace propagation for aircraft with propellers." Civil Aviation High Technologies 26, no. 3 (June 23, 2023): 103–13. http://dx.doi.org/10.26467/2079-0619-2023-26-3-103-113.
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The article presents the results of a study of the characteristics of the wake vortex of aircraft with turboprop engines. Using the example of the An-12 aircraft, it is shown that rotating propellers make a noticeable contribution to the propagation of the vortex trail behind the aircraft. This is proved by some studies, as well as numerous observations. It also describes a technique for studying the wake vortex of aircraft with propellers. The method is based on the method of discrete vortices. The relevance of such studies is due to the growing interest of carrier companies in aircraft with turboprop engines. It has been proven that when transporting passengers and cargo on such vessels over distances of 700–800 km, maintenance and fuel costs are reduced by about 30–40%. Therefore, the fleet of turboprop aircraft, such as An-22, An-70, An-12, as well as Tu-95, Il-38, C-130, etc., has been preserved so far. New turboprop aircraft are being developed and put into operation: A-400M, Il-114, Il-112M. The vortex trail behind such aircraft also poses a danger to other aircraft flying behind. A feature of the propagation of the wake vortex behind aircraft with propellers is the interaction of vortices coming off the airframe and vortices from the propellers. As a result, due to the rotation of all the screws in one direction, symmetry is broken in the propagation of vortices descending from the right and left halves of the wing. Therefore, it is important to understand how differently the vortices that descend from the airframe of an aircraft with turboprop engines behave. For the convenience of the study, the method of accounting for the effect of vortices from screws is integrated into a special calculation and software package, also based on the method of discrete vortices. In it, when calculating the characteristics of the wake vortex, the flight weight, speed and altitude of the aircraft, its flight configuration, atmospheric conditions, proximity of the earth, axial velocity in the core of the vortex and some other factors are taken into account. This complex has passed the necessary testing and state registration. A number of measures were carried out to validate and verify the developed complex, confirming the operability of the programs included in it and the reliability of the results obtained from it. The results of the study of the characteristics of the wake vortex behind the Antonov-12 aircraft in the form of vertical velocity spectra and fields of perturbed velocities at various distances from it are presented. It is shown that propellers noticeably affect the propagation of the wake vortex behind turboprop aircraft. This circumstance must be taken into account by the crews of aircraft flying behind such aircraft.
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Singh, Sunayna, Martin Sippel, and Sven Stappert. "Full-scale simulations of ‘In-Air Capturing’ return mode for winged reusable launch vehicles." Journal of Physics: Conference Series 2526, no. 1 (June 1, 2023): 012114. http://dx.doi.org/10.1088/1742-6596/2526/1/012114.
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Abstract The recent success of reusable launchers has become a driving force for sustainable launch technologies. An innovative approach proposed by DLR, involves winged rocket stages captured mid air and towed back to the launch site by an aircraft. This recovery concept known as ‘In-Air Capturing (IAC)’, shows potential for substantial cost reduction, when compared to existing return modes. In the light of the Horizon 2020 project FALCon, full-scale simulations and sub-scale flight testing were carried out for further development of the technology. The paper summarizes the full-scale studies performed within FALCon. The full-scale test cases are introduced and the simulation framework for analysis of trajectories is presented. Then, the IAC maneuver is analyzed through trajectory simulations. Major external disturbances coming from the wake of the aircraft and flexibility of the rope connecting the rocket stage to the aircraft (after capture) are also addressed.
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Zhelannikov, A. I., and A. N. Zamyatin. "Investigation of the influence of engine displacement along the aircraft wing on the propagation of a condensation trail." Civil Aviation High Technologies 25, no. 5 (October 23, 2022): 48–58. http://dx.doi.org/10.26467/2079-0619-2022-25-5-48-58.
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With the publication of this article, the authors continue their research into the interaction of vortex and condensation trails behind aircraft, which has begun in the previously published articles in the Civil Aviation High Technologies of the Moscow State Technical University of Civil Aviation. This paper presents the investigation results of the influence of engine displacement along the A320 aircraft wing on the development and propagation of a contrail. It should be clear that a contrail is a product of aviation fuel combustion in the engine and represents condensed moisture in the form of ice crystals, which is formed under certain conditions of the atmosphere. As numerous studies and observations have shown, contrails can affect the heat exchange processes in the atmosphere and deteriorate the environment contributing to the greenhouse effect. This is especially true for the areas where numerous airways pass. It was noted that inboard engine displacement or, vice versa, outboard affects the development and propagation of a contrail. Therefore, when forming the aerodynamic configuration of the future aircraft, designers should take this aspect into account. The fact is that a wake vortex, which is formed behind the aircraft, impacts the contrail in different ways, depending on the engine proximity to the vortices, trailing from the airframe. Let us point out that a wake vortex is the area of the disturbed airflow behind the aircraft, generated as a result of its movement. A contrail, interacting with a vortex one, dissipates in the atmosphere, and the substances, composing a contrail, lose their concentration. It is also significant that a contrail, interacting with a wake vortex, can reveal its structure and visualize the wake vortex propagation and decay processes. In this paper, a special computational software application, based on the discrete vortex method, was used to study the influence of engine displacement along the A320 aircraft wing on the development and propagation of a contrail. When calculating the characteristics of a wake vortex, it takes into consideration the aircraft weight, speed and altitude, flight configuration, ambient conditions, axial velocity in the vortex core and some other factors. This complex passed the required testing and the state registration. A variety of activities was undertaken to validate and verify the developed complex, confirming the operability of its programs and the reliability of the results obtained. The results obtained allow us to understand how engine displacement along the A320 aircraft wing influences the contrail development and propagation.
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Huber, F. W., P. D. Johnson, O. P. Sharma, J. B. Staubach, and S. W. Gaddis. "Performance Improvement Through Indexing of Turbine Airfoils: Part 1—Experimental Investigation." Journal of Turbomachinery 118, no. 4 (October 1, 1996): 630–35. http://dx.doi.org/10.1115/1.2840918.
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This paper describes the results of a study to determine the performance improvements achievable by circumferentially indexing successive rows of turbine stator airfoils. An experimental/analytical investigation has been completed that indicates significant stage efficiency increases can be attained through application of this airfoil clocking concept. A series of tests was conducted at the National Aeronautics and Space Administration’s (NASA) Marshall Space Flight Center (MSFC) to experimentally investigate stator wake clocking effects on the performance of the Space Shuttle Main Engine Alternate Fuel Turbopump Turbine Test Article. Extensive time-accurate Computational Fluid Dynamics (CFD) simulations have been completed for the test configurations. The CFD results provide insight into the performance improvement mechanism. Part one of this paper describes details of the test facility, rig geometry, instrumentation, and aerodynamic operating parameters. Results of turbine testing at the aerodynamic design point are presented for six circumferential positions of the first stage stator, along with a description of the initial CFD analyses performed for the test article. It should be noted that first vane positions 1 and 6 produced identical first to second vane indexing. Results obtained from off-design testing of the “best” and “worst” stator clocking positions, and testing over a range of Reynolds numbers are also presented. Part two of this paper describes the numerical simulations performed in support of the experimental test program described in part one. Time-accurate Navier–Stokes flow analyses have been completed for the five different turbine stator positions tested. Details of the computational procedure and results are presented. Analysis results include predictions of instantaneous and time-average midspan airfoil and turbine performance, as well as gas conditions throughout the flow field. An initial understanding of the turbine performance improvement mechanism is described.
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Raffel, Markus, James T. Heineck, Edward Schairer, Friedrich Leopold, and Kolja Kindler. "Background-Oriented Schlieren Imaging for Full-Scale and In-Flight Testing." Journal of the American Helicopter Society 59, no. 1 (January 1, 2014): 1–9. http://dx.doi.org/10.4050/jahs.59.012002.
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Background-oriented schlieren (BOS) methods suited for large-scale and in-flight testing are presented with special emphasis on the detection and tracing of blade tip vortices in situ. Retroreflective recording and photogrammetric epipolar analysis for the computation of the vortices' spatial coordinates in the wind tunnel are described. Feasibility and fidelity of reference-free BOS in conjunction with natural formation backgrounds and related evaluation methods are discussed, additionally, illustrating their simplicity and robustness. Results of successful image acquisition from a chaser aircraft are presented allowing vortex wakes to be identified at a wide range of flight attitudes, including complex maneuvers.
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Hall, David S., Rhodri Jervis, Louis F. J. Piper, Alexandra L. Kersting, and Clare P. Grey. "Battery Degradation and Lifetime – Studies within the Faraday Institution on NMC811/Graphite Full Cells." ECS Meeting Abstracts MA2022-01, no. 2 (July 7, 2022): 341. http://dx.doi.org/10.1149/ma2022-012341mtgabs.
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Lithium-ion batteries (LIBs) find use in a wide range of applications, each of which has its own design specifications and practical requirements. With regards to the role of LIBs in mitigating carbon emissions, and therefore climate change, it is desirable to support the rapidly growing adoption of electric vehicles and renewable grid-storage systems via development of higher energy density, lower cost, and improved rate capability. However, the design of energy-dense, low-cobalt, and/or high-rate cell chemistries is impeded by inherent trade-offs with cycling and calendar lifetimes. A key goal for the automotive and utilities industries is therefore to predict battery lifetime for new cell designs and chemistries at a very high level of confidence, for example through improved understanding of the physical and chemical processes that determine the state of health of battery systems. As part of the Faraday Institution, the UK’s independent institute for electrochemical energy storage technology, the Battery Degradation Project has built new understanding of the underlying physical and chemical processes that can lead to degradation in energy-dense NMC811/graphite lithium-ion cells as a model system. Led by the University of Cambridge (Clare Grey PI) in collaboration with eight UK universities, the research consortium is working closely with industry partners to create a new hub for lithium-ion battery research and to address key challenges and opportunities in the field. This presentation will give an overview of the research consortium’s diverse membership, key milestones, and technical progress. To date, the consortium has been applying a variety of analytical techniques to study degradation processes in NMC811/graphite cells. For example, electrochemical testing and operando solid-state 7Li nuclear magnetic resonance spectroscopy (NMR) were combined to monitor processes in both electrodes individually, including Li-ion mobility and its changes with temperature.1 The method is now being applied to understand how the dynamics are affected by long-term structural damage to the NMC811 material. A series of differential voltage analysis experiments have been paired with operando X-ray diffraction measurements to propose the mechanism behind a critical ‘turning point’ in NMC811/graphite cells, following which degradation accelerates significantly.2 New operando cell designs have been developed to measure changes in cell pressure,3 which are being paired with solution NMR spectroscopy,4 and differential electrochemical mass spectrometry to quantify electrolyte oxidation. The role and rate of transition-metal dissolution in cells under stressed cycling conditions, namely cycling at high temperature (60 °C) and high upper cut-off voltages (4.4, 4.6 V), has been investigated.5 Scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDX) measurements were coupled with time-of-flight secondary-ion mass spectrometry (Tof-SIMS) to observe the Al-containing phases at NMC811 surfaces and grain boundaries.7 New spectroscopic methods are also being developed, including Kerr-gated Raman, which allows sensitive measurements of electrode materials and electrolytes with lower background signal than conventional Raman spectroscopy.6 Finally, X-ray computed tomography methods have been developed that enable operando imaging and spectroscopic mapping of heterogeneities at a sub-particle length scale and across large areas of electrodes, which are being applied to study the origins of microstructural defects, cracking, and redox activity during charging, cycling, or storage.8,9 Reference s: K. Märker, C. Xu, and C. P. Grey, J. Am. Chem. Soc., 142, 17447–17456 (2020). W. M. Dose, C. Xu, C. P. Grey, and M. F. L. De Volder, Cell Rep. Phys. Sci., 1, 100253 (2020). N. Ryall and N. Garcia-Araez, J. Electrochem. Soc., 167, 110511 (2020). B. L. D. Rinkel, D. S. Hall, I. Temprano, and C. P. Grey, J. Am. Chem. Soc., 142, 15058–15074 (2020). Z. Ruff, C. Xu, and C. P. Grey, J. Electrochem. Soc., 168, 060518 (2021). L. Cabo-Fernandez, A. R. Neale, F. Braga, I. V. Sazanovich, R. Kostecki, and L. J. Hardwick, Phys. Chem. Chem. Phys., 21, 23833–23842 (2019). J. Lee, H. Amari, M. Bahri, Z. Shen, C. Xu, Z. Ruff, C. P. Grey, O. Ersen, A. Aguadero, N. D. Browning, and B. L. Mehdi, Batter. Supercaps, 4, 1813–1820 (2021). T. M. M. Heenan, A. Wade, C. Tan, J. E. Parker, D. Matras, A. S. Leach, J. B. Robinson, A. Llewellyn, A. Dimitrijevic, R. Jervis, P. D. Quinn, D. J. L. Brett, and P. R. Shearing, Adv. Energy Mater., 10, 2002655 (2020). C. Tan, A. S. Leach, T. M. M. Heenan, H. Parks, R. Jervis, J. N. Weker, D. J. L. Brett, and P. R. Shearing, Cell Rep. Phys. Sci., 100647 (2021).
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Saetti, Umberto, and Batän Buäday. "Tiltrotor Simulations with Coupled Flight Dynamics, State-Space Aeromechanics, and Aeroacoustics." Journal of the American Helicopter Society, 2023. http://dx.doi.org/10.4050/jahs.69.012003.
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This article describes the development, implementation, and validation of a generic tilt-rotor simulation model with coupled flight dynamics, state-variable aeromechanics, and aeroacoustics. A major novelty of this work lies in the integration of the flight dynamics with a state-space free-vortex wake code that adopts a near-wake vortex-lattice model. This way, the flight dynamics are augmented by the vortex wake dynamics so that the coupled flight and wake dynamics are self-contained and inherently linearizable. The model is implemented for a Bell XV-15 tiltrotor and validated against U.S. Army/NASA XV-15 flight-test data and other data in the literature. Flight control design is performed to provide desired stability, performance, and handling-quality properties and to allow for a fully autonomous transition between hover in helicopter mode and high-speed flight in aircraft mode. The simulation model has clear applications in the development and testing of advanced flight control laws, aeromechanics analysis, and the prediction of aerodynamically generated noise in generalized maneuvering flight.
Dissertations / Theses on the topic "Wake Flight Testing"
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Rogge, Matthew Douglas. "In-process sensing of weld penetration depth using non-contact laser ultrasound system." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31698.
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Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2010.Committee Chair: Ume, Charles; Committee Member: Chen, Ye-Hwa; Committee Member: Michaels, Jennifer; Committee Member: Sadegh, Nader; Committee Member: Vachtsevanos, George. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Poggi, Francesco. "Bending properties of commercial wood-based panels by NDT methods." Thesis, Linnéuniversitetet, Institutionen för skog och träteknik (SOT), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-66162.
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This thesis work focuses mainly on the application of non-destructive testing (NDT) methods on wood-based panels (WBP) in order to estimate the bending properties. To prove the accuracy and applicability of these methods on WBP, their results are correlated with results from a standardized static bending test. The behavior in different climate conditions and the application on panels of larger sizes is also questioned to provide an indication about strong points and boundaries of NDT methods applied on WBP.The bending properties are of major importance, especially for materials suited to bear loads. Bending stiffness, represented by the modulus of elasticity (MOE), is an expression of the deflection rate of a material under load. The bending strength, represented by the modulus of rupture (MOR), is an expression of the maximum load withstood by a material before rupture.Before testing, the material is acclimatized in three climate conditions: dry (20°C, 35% RH), standard (20°C, 65% RH) and wet (20°C, 85% RH), to understand the bending properties variation and how the NDT methods are affected by the variation in moisture content.The materials used are seven types of WBP, in particular four types of particleboards (PB), one type of high-density fiberboard (HDF), one type of dual density PB (with high and low density areas along the production direction) and one type of light-weight panel (Board-on-stiles, a composite panel of HDF, PB and paper honeycomb).To test the bending properties the following NDT methods are considered: transversal resonance vibration and longitudinal resonance vibration with the use of the BING system and the time-of-flight with the use of Fakopp Ultrasonic Timer and Silvatest Trio. The resonance vibration methods, transversal and longitudinal, are based on the relation between resonance vibration properties and bending properties of a material. The relation with bending properties also exists for the stress wave velocity (SWV) through a material, calculated with the time-of-flight method. The dynamic MOE resulting from these tests is then correlated with the static MOE and MOR from the static bending test.The NDT methods resulted to be reliable on WBP, with generally high levels of correlation between dynamic MOE and static MOE and MoR. The highest correlation value for MoE is with the transversal resonance vibration while the highest for MOR is with the longitudinal resonance vibration. The results of the dynamic MOE for all the NDT methods are higher than the static MOE, as confirmed also in the literature; the average ratio between the dynamic and the static MOE is, for example, up to 1,6 for WBP in standard climate condition, tested with Fakopp U.T.. These results are extremely higher than values suggested by previous studies. Moreover, the ratio increases with increasing relative humidity of the climate condition. The results from the tests on larger sizes suggest a possible application in this field. The time-of-flight method is suitable for in-plane uniform materials, like the PB and HDF, while the transversal resonance methods give also a good representation of the properties of the dual density PB and the light-weight panel.
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Carbol, Ladislav. "Měření akustických vlastností stavebních materiálů pomocí pseudonáhodné sekvence." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-355599.
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The thesis deals with research of pulse compression of the acoustic signal in terms of applications in civil engineering. Based on the study and analysis of these methods, automated measuring equipment for non-destructive testing with pseudorandom sequence of maximum length and automated signal analysis, have been designed and implemented. In a single test cycle are obtained three parameters that characterize the linear and nonlinear behavior of the sample. A nonlinear parameter, Time of Flight of ultrasonic wave in the sample is further in the work compared with the conventional pulse measuring, and spectral analysis is compared with the method impact-echo. Functionality and optimization of the testing method was performed on a total of three sets of test pieces made of various building materials. The experiments proved simple result interpretation, and high sensitivity to structural damage associated with temperature loading. The results were correlated with conventional nondestructive methods and by destructive testing was measured change in compressive strength and flexural strength. This work also includes continual measurement of fundamental frequency influenced by moisture on a mortar sample. Use of pulse compression signal is in the civil engineering quite unusual. Only in recent years this topic is discussed in scientific articles with increasing frequency. Great potential lies in the association of three test methods into a single. Beneficial is high test speed and measurement reproducibility, but also theoretical possibility of testing massive test elements.
Books on the topic "Wake Flight Testing"
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Garodz, Leo J. Vortex characteristics of C5A/B, C141B, and C130E aircraft applicable to ATC terminal flight operations tower fly-by data. Silver Spring, Md: U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, Environmental Research Laboratories, Air Resources Laboratory, 1991.
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L, Clawson K., and Air Resources Laboratory (U.S.), eds. Vortex characteristics of C5A/B, C141B and C130E aircraft applicable to ATC terminal flight operations tower fly-by data. Silver Spring, Md: U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, Environmental Research Laboratories, Air Resources Laboratory, 1991.
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Vortex characteristics of C5A/B, C141B and C130E aircraft applicable to ATC terminal flight operations tower fly-by data. Silver Spring, Md: U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, Environmental Research Laboratories, Air Resources Laboratory, 1991.
Find full textBook chapters on the topic "Wake Flight Testing"
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Bai, Xuejiao, and Haijiang Zhu. "Research on Finite Element Analysis Method of Laser Ultrasonic Velocity Measurement." In Proceedings of the 2022 International Conference on Smart Manufacturing and Material Processing (SMMP2022). IOS Press, 2022. http://dx.doi.org/10.3233/atde220833.
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As a new nondestructive testing method, the accurate measurement of laser ultrasonic velocity is of great significance for judging the internal crack defects of composites, calculating the elastic modulus, residual stress and grain size. Based on the finite element analysis method, the thermoelastic effect of laser induced ultrasonic vibration, the time-of-flight method and laser grating method for measuring ultrasonic velocity are studied in this paper. Firstly, the waveforms of laser point source, line source and laser grating are compared and analyzed. Secondly, the error analysis of the wave velocity under different radius laser point source, different half width laser line source and different grating spacing is carried out. The simulation results show that the laser grating method has higher stability and smaller measurement error. In addition, this method is less affected by other waves and the external environment. This paper provides a basis for improving the measurement accuracy of laser ultrasonic velocity and further applying laser ultrasonic velocity to nondestructive testing and measurement of related physical quantities.
Conference papers on the topic "Wake Flight Testing"
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Tierney, Charles, Nicholas Jaffa, David Reich, and Sven Schmitz. "Scaled Model Testing of Coaxial Rotor Hub Flows." In Vertical Flight Society 77th Annual Forum & Technology Display. The Vertical Flight Society, 2021. http://dx.doi.org/10.4050/f-0077-2021-16877.
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Rotor hub parasite drag remains a primary obstacle to improving the forward-flight capabilities of helicopters. As part of a rotor hub flow physics project at the Vertical Lift Research Center of Excellence (VLRCOE) at Penn State, this investigation was designed to improve the understanding of the interactional aerodynamics and wake flow physics of counter-rotating coaxial rotor hubs and explore designs for reducing the rotor hub drag factor, Kfe. These experiments measured the time-averaged and time-varying drag on four rotor hub designs, each with unique blade stubs. The four shapes tested were the DBLN 526 airfoil, 3.25:1 Rectangle, 4:1 Ellipse, and the novel profile named the Optimized Cambered Shape (OCS). Load data was collected at four Reynolds numbers ranging from 3.77×105 to 1.51×106 and advance ratios ranging from .25 to .6. Additionally, stereoscopic particle-image velocimetry (SPIV) measured the three velocity components at two downstream locations in the wake of the DBLN 526 rotor hub at Re=1.13×106 and advance ratios of .25 and .6, providing insight into and visualizing the development of the wake. Presented here is the compiled load data and calculated Kfe from these experiments, as well as the flow fields at the near- and midwake locations, with discussion of new knowledge gained of the coaxial rotor hub wakes.
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Brown, Anthony, and Matthew Bastian. "Wake Vortex Flight Measurements and Tactical Aircraft WVE Design and Flight Testing Requirements." In 2008 U.S. Air Force T&E Days. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2008. http://dx.doi.org/10.2514/6.2008-1651.
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Steen, Meiko, Mirko Stanisak, Thomas Feuerle, and Peter Hecker. "In-Flight Testing of Airborne LIDAR for Wake Vortex Detection, Characterization and Tracking." In 6th AIAA Atmospheric and Space Environments Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2014. http://dx.doi.org/10.2514/6.2014-2336.
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Saetti, Umberto, and Batin Bugday. "Generic Tilt-Rotor Simulation Model with Coupled Flight Dynamics, State-Variable Aeromechanics, and Aeroacoustics." In Vertical Flight Society 79th Annual Forum & Technology Display. The Vertical Flight Society, 2023. http://dx.doi.org/10.4050/f-0079-2023-18110.
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This paper describes the development, implementation, and validation of a generic tilt-rotor simulation model with coupled flight dynamics, state-variable aeromechanics, and aeroacoustic. A major novelty of this work lies in the integration of the flight dynamics with a state-space free-vortex wake code that adopts a near-wake vortex-lattice model. This way, the flight dynamics are augmented by the vortex wake dynamics so that the coupled flight and wake dynamics is self-contained and inherently linearizable. The model is implemented for a Bell XV-15 tiltrotor and validated against U.S. Army/NASA XV-15 flight-test data and other data in the literature. Flight control design is performed to provide desired stability, performance, handling-quality properties and to allow for a fully-autonomous transition between hover in helicopter mode and high-speed flight in aircraft mode. The simulation model has clear applications in the development and testing of advanced flight control laws, aeromechanics analysis, and in the prediction of aerodynamically-generated noise in generalized maneuvering flight.
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Tritschler, John, Joseph Milluzzo, and John Holder. "Performance Effects of Hover In-Ground-Effect over Sloped Terrain." In Vertical Flight Society 75th Annual Forum & Technology Display. The Vertical Flight Society, 2019. http://dx.doi.org/10.4050/f-0075-2019-14520.
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The present work reports the results of a research investigation into the performance effects of hovering over sloping terrain as characterized in both laboratory-scale testing of an isolated rotor as well as flight testing of a UH-72A helicopter. The design of the experiment included variation in the slope magnitude, rotor hub height, thrust/power setting, and aircraft orientation with respect to the slope (for the flight test data). In addition to performance measurements, flow field measurements of the laboratory flows were computed via particle image velocimetry, and rotor wake visualizations from flight testing were created via background-oriented Schlieren post-processing techniques. The results show that hovering over sloped terrain results in performance effects that are both nonintuitive and operationally significant. Additionally, the hover performance data collected over level terrain show that inground-effect hover performance is truly a complicated, interdependent relationship that includes multiple specifying conditions; it is not simply a one-dimensional function of hub height above the ground plane. Lastly, a comparison of the flow field measurements from laboratory testing and the rotor wake visualization from flight testing is presented to speculate on the fundamental flow field mechanisms at play and propose an approach for a more rigorous reconciliation of these two data sets in future studies.
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Staruk, William, Evan Bonny, Lauren Butt, Cody Gray, Garrett Hennig, Diego Represa, and Richard Toner. "Wind Tunnel Testing and Analysis of a Rigid, Variable Speed Rotor for eVTOL Applications." In Vertical Flight Society 76th Annual Forum & Technology Display. The Vertical Flight Society, 2020. http://dx.doi.org/10.4050/f-0076-2020-16411.
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Many electric vertical take-off and landing (eVTOL) aircraft intended for the urban air mobility (UAM) market are currently being designed with multirotor configurations using variable speed fixed-pitch, rigid rotors for lift. These types of rotors, which are similar in construction to general aviation airplane propellers, are simpler than helicopter rotors and have no moving parts in the rotating frame. This paper discusses wind-tunnel testing of a full-scale, UAM multirotor size, fixed-pitch, rigid rotor with a focus on vibratory blade loads and on the ability to predict these loads with comprehensive analysis. Test results show that vibratory loads are very high, with peak-to-peak magnitudes up to three times greater than the steady component. Correlation of test data to comprehensive analysis using geometrically exact composite beam structural elements and dynamic inflow wake modeling captures the trends in the steady and vibratory loads, but under-predicts the magnitudes by up to 50%. The paper also discusses the physical sources of the observed vibratory loads and suggests potential options for mitigating their magnitude.
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Welsh, Jake, and David Peters. "Floquet Instability in Periodically Reversing Flows." In Vertical Flight Society 79th Annual Forum & Technology Display. The Vertical Flight Society, 2023. http://dx.doi.org/10.4050/f-0079-2023-18107.
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Current 3-D finite-state wake models are incapable of simulating a maneuver in which the sign of the free-stream velocity changes direction and the rotor enters its own wake - as might occur in the case of a helicopter which ascends and then descends. It is the purpose of this work to create a 2-D finite-state wake model which is capable of handling changes in free-stream direction as a precursor to development of a 3-D model that can do the same. The 2-D finite-state model used for reentry modifications is an existing model created by Peters, Johnson, and Karunamoorthy. By the addition of a parameter which changes the sign of the free-stream accordingly, a model capable of handling forward and backward flight is developed and tested. Upon testing of the model for an oscillatory free-stream which changes direction, it was discovered that the presence of a singularity causes the system to become unstable. This behavior was determined to be due to a Floquet instability which occurs in periodic free-streams that reverse direction.
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Keller, Jeffrey, Mark J., Ondrej Juhasz, Robert McKillip, Daniel Wachspress, and Mark Tischler. "Linearized Inflow and Interference Models from High Fidelity Free Wake Analysis for Modern Rotorcraft Configurations." In Vertical Flight Society 76th Annual Forum & Technology Display. The Vertical Flight Society, 2020. http://dx.doi.org/10.4050/f-0076-2020-16290.
Full textAbstract:
Linearized inflow models have been used to represent dynamic wake effects for control law development and flight dynamics simulation of conventional main rotor / tail rotor helicopters. With the current focus in the industry toward high-speed concepts and electric vertical take-off and landing (eVTOL) aircraft, modern rotorcraft designs are trending away from the conventional main rotor / tail rotor configuration for which low-order dynamic inflow models have been applied and validated. Configurations currently in design and flight testing stages include coaxial, coaxialcompound, tiltrotor, multi-rotor, and augmented lift concepts that involve strong rotor-rotor and rotor-airframe aerodynamic interactions. A procedure for extracting linearized inflow and interference models from higher fidelity comprehensive analyses suitable for advanced rotorcraft configurations has been developed and applied to a modern lift-offset coaxial rotorcraft. A second-order inflow model structure including wake distortion effects due to pitch and roll motion is shown to capture the critical dynamic response characteristics when compared to a nonlinear flight dynamics simulation coupled with a free wake model. This second-order model structure is more accurate and provides better prediction of flight controller performance metrics than a more conventional Pitt-Peters model structure.
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Taymourtash, Neda, Daniele Zagaglia, Alex Zanotti, Giuseppe Gibertini, and Giuseppe Quaranta. "Towards a Wind Tunnel Testing Environment for Rotorcraft Operations Close to Obstacles." In Vertical Flight Society 75th Annual Forum & Technology Display. The Vertical Flight Society, 2019. http://dx.doi.org/10.4050/f-0075-2019-14640.
Full textAbstract:
The correct identification of the aerodynamic loads due to interaction between rotorcraft and obstacles requires to run computationally intensive numerical models characterized by a high level of uncertainty. Wind tunnel data can be used as a source of information to improve those models. The present paper investigates the aerodynamic interaction of a helicopter and ship airwake exploiting wind tunnel data. A series of wind tunnel experiment, using a scaled helicopter model and Simple Frigate Shape 1, has been performed to measure forces and moments acting on the rotor, while the helicopter is approaching the flight deck. In addition, the velocity components along the longitudinal symmetry plane of the rotor have been visualized using PIV technique. With the rotor positioned at the starting point of the landing trajectory, the load measurements are used to modify the distribution of the inflow over the rotor in multibody simulation environment, in order to generate same loads, including thrust, torque and in-plane moments. Then, an identification algorithm is developed to capture the effect of ship airwake on the rotor loads during the maneuvers, modeling it as an external gust to the rotor inflow. The gust velocity is obtained through an optimization algorithm with the objective of generating same load coefficients as the experiment. The simulation results show that the same load coefficients as the experiment can be generated by implementing a linear gust over the rotor with a magnitude that changes as the rotor moves through the wake of ship. The experiment showed that this test setup could be used for identification of aerodynamic interaction to be used for maneuver analysis.
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Keller, Jeffrey, Mark Tischler, Robert M., Daniel Wachspress, and Ondrej Juhasz. "Linearized Inflow and Interference Models from High Fidelity Free Wake Analysis for Modern Rotorcraft Configurations." In Vertical Flight Society 75th Annual Forum & Technology Display. The Vertical Flight Society, 2019. http://dx.doi.org/10.4050/f-0075-2019-14638.
Full textAbstract:
Linearized inflow models have been used to represent dynamic wake effects for control law development and flight dynamics simulation of conventional main rotor / tail rotor helicopters. With the current focus in the industry toward high-speed concepts and electric vertical take-off and landing (eVTOL) aircraft, modern rotorcraft designs are trending away from the conventional main rotor / tail rotor configuration for which low-order dynamic inflow models have been applied and validated. Configurations currently in design and flight testing stages include coaxial, coaxialcompound, tiltrotor, multi-rotor, and augmented lift concepts that involve strong rotor-rotor and rotor-airframe aerodynamic interactions. To support current trends in rotorcraft designs, it is necessary to revisit the low-order inflow model structure and application with respect to modern rotorcraft analysis and flight simulation methods. Research and development in recent years has focused on methods to extract equivalent linearized inflow / interference models from high-fidelity nonlinear rotorcraft aeromechanics models. This paper describes continuing work to develop an automated method for linearized inflow model extraction from high-fidelity rotorcraft aerodynamic / wake models. Emphasis is placed on the formulation of generic inflow model structures for single and coaxial rotor systems that capture relevant physical phenomena without over-parameterizing the low-order state-space inflow model.