Comprehensive Analysis, Prediction, and Validation of UH-60A Blade Loads in Unsteady Maneuvering Flight
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Flight and wind tunnel tests were conducted and multidiscipline computer programs were developed as part of investigations of active control technology conducted at the NASA Langley Research Center. Unsteady aerodynamics approximation, optimal control theory, optimal controller design, and the Delta wing and DC-10 models are described. The drones for aerodynamics and structural testing (DAST program) for evaluating procedures for aerodynamic loads prediction and the design of active control systems on wings with significant aeroelastic effects is described as well as the DAST model used in the wind tunnel tests.
Aeroelasticity
Delta wing
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A review is presented of some of the early rotor systems flight research leading to the present comprehensive NASA/Army rotor system airloads program with the UH-60 helicopter. The experimental and analytical plans and progress for this program are described, including the design and development of a rotor blade which incorporated 242 pressure transducers buried in the surface of the blade, and also the development of calibration hardware for regular calibration and testing of the transducers. Supporting analytical developments based on the comprehensive analytical model of rotorcraft aerodynamics and dynamics (CAMRAD) and various CFD codes are discussed. The highly instrumented UH-60 as well as companion programs of full-scale and model wind tunnel tests of the UH-60 rotor with identical instrumentation will provide the opportunity to explore a full range of rotor experiments and the data necessary to validate the advanced methodologies under development.
Helicopter rotor
Instrumentation
Full scale
Flight test
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A methodology for the coupling of an advanced computational fluid dynamics method based on an overset grid flow-solver and an advanced computational structural dynamics method based on a finite element analysis is presented. Various procedures for the fluid-structure interactions modeling along with their limitations are also discussed. The flight test data for the four-bladed UH-60A Blackhawk helicopter rotor is chosen for the validation of the results. Convergence and accuracy are tested by numerical experiments with a single-bladed rotor. A comparison of airload predictions with flight test data as well as with a rigid blade case is presented. Grid and interpolation related issues for this aeroelastic application are described.
Solver
Interpolation
Helicopter rotor
Aeroelasticity
Unstructured grid
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In this paper, a methodology is presented to size an aircraft wing-box accounting for steady and dynamic loads combined with active control. Several aerodynamic corrections are used and benchmarked to ensure a consistent level of fidelity during the load analysis. Reduced order models (ROM) of the aircraft movables, gust loads and maneuvers loads are derived from rigid CFD analysis and used as substitutes for the loads in the aeroelastic simulation.
Aeroelasticity
Wing loading
Wing configuration
Flight Dynamics
Aileron
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Aeroelasticity
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The experimental data for a 4-bladed soft-inplane hingeless main rotor is used to validate a comprehensive aeroelastic analysis. A finite element model has been developed for the rotor blade which predicts rotating frequencies quite well, across a range of rotation speeds. The helicopter is trimmed and the predicted trim-control angles are found to be in the range of measured values for a variety of flight speeds. Power predictions over a range of forward speeds also compare well. Finally, the aeroelastic analysis is used to study the importance of aerodynamic models on the vibration prediction. Unsteady aerodynamics and free-wake models have been investigated.
Aeroelasticity
Helicopter rotor
Trim
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In this paper, a comprehensive computational modeling study of the unsteady aerodynamic environment around a warship with a helicopter is performed. An experimental validation exercise is also conducted, comparing computational fluid dynamics (CFD) results of the airwake calculated for a reduced-scale model of the isolated Landing Helicopter Assault (LHA) model with high-quality particle image velocimetry experimental data provided by the NASA AMES Research Center. Comparisons of the results generally obtain agreement, indicating that the CFD numerical method is able to resolve the large-scale turbulent airflow. Building on this, a numerical simulation of a real Robin helicopter, immersed in the unsteady airwakes of a full-scale Amphibious Assault Ship (AAS), is performed. The aerodynamic simulation of the influence on the coupled airflow of warship–helicopter is explored and compared with that of the solitary ship airflow field and the superposition airwakes, where the vortex patterns and pressure on the ship surface, as well as the velocity distribution, are circumvented. As a further step, dynamic landing analysis of the airflow field for a shipborne helicopter is implemented at an important location through the landing path for headwind. The aerodynamic characteristics of a helicopter during a flight deck landing are also explored for the unsteady ship airwakes impacting on rotor force during shipboard landings. In addition, different shipboard landing paths of the helicopter are comparatively investigated for obtaining an optimal landing path decision. The present study demonstrates an effective aerodynamic analysis and robust numerical approach, which creates a solid foundation supporting further alternative evaluations of ship airflow fields.
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