Browse Topic: Tools and equipment
This paper presents a meshless large eddy simulation approach for rotorcraft wake prediction, using a vortex particle method accelerated on GPUs. The solver couples a rotor model with a vortex particle wake model, employing the Fast Multipole Method for computational efficiency and implementing viscous diffusion through Particle Strength Exchange and Core Spreading Methods. GPU acceleration achieves speed-ups of up to 10x compared to CPU execution. The solver’s predictions are validated against experimental data, showing excellent agreement. Effects of time step size, numerical integration schemes, viscous models, and particle overlap factors on simulation accuracy and computational cost are systematically analyzed. This GPU-based vortex particle framework provides a fast, accurate, and scalable tool for rotorcraft wake simulations.
Rotorcraft continue to experience higher fatal accident rates compared to fixed-wing aircraft, primarily due to low altitude flight operations and reduced situational awareness in complex environments. A critical factor is the limited availability of accurate, up-to-date information on helipads and surrounding obstacles - such as trees, poles, and buildings - that pose significant risks during takeoff and landing. Existing resources, including the Federal Aviation Administration's heliport registry, are often outdated and incomplete, particularly for private or state-operated sites, and fail to report nearby obstacles. This lack of up-to-date data is largely due to privacy restrictions at certain locations and the high cost associated with comprehensive obstacle surveys. To address this challenge, we develop a deep learning (DL) framework that automatically detects helipads and nearby obstacles from high-resolution satellite imagery. Our approach combines Mask R-CNN for precise pixel
The Shake-The-Box technique was applied to experimentally quantify the time-resolved volumetric flow field around a free-flying quadcopter UAV with an overall span of about 0.5 m. State-of-the-art LED illumination and high-speed camera equipment was combined with modern Lagrangian tracer particle tracking and data assimilation techniques, facilitating a measurement volume larger than 1.5m3. The setup allowed for both hover and limited maneuvering of the quadcopter, while resolving even small details of the complex interactional aerodynamics. In hover out of ground effect, the four individual rotor wakes merged into a single jet within a few rotor radii below the rotor planes. Evaluating the mass and momentum fluxes over suitable control volumes yields accurate estimates for the quadcopter's total thrust, the asymmetric thrust distribution between front and back rotors, and the entrainment of external flow through turbulent mixing. Hover in ground effect decreases the power requirement
This paper documents the re-evaluation and updates to the previous Partial Regime Recognition Spectrum effort for the MH-47G using Structural Usage Monitoring System (SUMS). Further validation of the SUMS algorithm allowed for additions to the spectrum. These additions include more refined categorization of turn and partial power descent regimes based on angle of bank and descent rates, respectively; high load prorates for turns, partial power descents, level flight, and climbs based on the Cruise Guide Indicator; exceedances of maximum density altitude; and use of occurrences for Landing and Run-On Landing regimes. Additional years of flight data from 2013 to 2019 were included in this effort. The updated usage spectrum for the Army MH-47G aircraft has been delivered to the OEM (Original Equipment Manufacturer). The OEM calculated new fatigue lives and updated the "Fatigue Substantiation Report", which will soon be fielded.
Coupling numerator models are a well-established tool for predicting the closed-loop dynamics of multiple-input multiple-output systems. They describe the input-output dynamics of the open-loop path in a partially controlled system given tight controls and thus may serve as an approximation of the actual dynamics "seen" by the single-axis controller in a controlled multiple-input multiple-output plant. Such models can therefore be employed for a decentralized initial design of multivariable controllers. This paper presents a new, unifying approach for the computation of such constrained input-output dynamics. Connections to existing methods in the literature are established and a general procedure for state-space calculations is given. The use of coupling numerator models for controller design is motivated and different decoupling structures are discussed. The controller design is illustrated using a coupled high-order helicopter model.
ABSTRACT The impact of hover download on rotorcraft design has long been recognized, though analytical focus on the issue has been intermittent, for both technical and programmatic reasons. Advanced models employed on high performance computer systems have shown impressive ability to capture observed behavior, though physics-based tools better suited to routine early stage design analysis are highly desirable. Prior papers conducted an initial assessment the ability of several contemporary "mid-fidelity" analysis tools to compute download and rotor/airframe interaction on helicopters and compound rotorcraft in hover, with initial studies focusing on single rotor aircraft operating out of ground effect. This paper extends this work to the consideration of other rotor configurations (e.g., tiltrotor/side-by-side and coaxial cases); given the development and prospective use of multiple new vehicles featuring these design elements an assessment of this capability is judged timely. In
ABSTRACT Accurate prediction of aeroelastic coupling between rotor wake and structure remains a key challenge to the development of advanced rotorcraft. Limitations of existing analysis tools to predict such aeroelastic interactions, notably empennage buffeting effects, have resulted in costly late-cycle design changes in multiple rotorcraft development programs, including the UH-60A and AH-64A. Aeromechanical phenomena involving interactions of the fuselage and rotor wake are complex, interdisciplinary, and three-dimensional in nature. For this reason, full vehicle CFD/CSD coupled analysis is essential to accurately capture the mutually dependent interactions between the aerodynamic loads and the aeroelastic response associated with these phenomena. The current state-of-the-art in rotorcraft analysis involves CFD/CSD coupled analysis of aeroelastic rotors and wings, but rigid representations of the fuselage and empennage structures (Ref. 1). To address this limitation, an elastic
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