A Unified Assessment of Fast Floquet, Generalized Floquet, and Periodic Eigenvector Methods for Rotorcraft Stability Predictions
About: This article is published in Journal of The American Helicopter Society.The article was published on 2013-10-01. It has received 29 citations till now. The article focuses on the topics: Floquet theory.
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TL;DR: In this article, an investigation on dynamic stall suppression capabilities of combustion-powered actuation (COMPACT) applied to a tabbed VR-12 airfoil is presented.
Abstract: An investigation on dynamic-stall suppression capabilities of combustion-powered actuation (COMPACT) applied to a tabbed VR-12 airfoil is presented In the first section, results from computational fluid dynamics (CFD) simulations carried out at Mach numbers from 03 to 05 are presented Several geometric parameters are varied including the slot chordwise location and angle Actuation pulse amplitude, frequency, and timing are also varied The simulations suggest that cycle-averaged lift increases of approximately 4% and 8% with respect to the baseline airfoil are possible at Mach numbers of 04 and 03 for deep and near-deep dynamic-stall conditions In the second section, static-stall results from low-speed wind-tunnel experiments are presented Low-speed experiments and high-speed CFD suggest that slots oriented tangential to the airfoil surface produce stronger benefits than slots oriented normal to the chordline Low-speed experiments confirm that chordwise slot locations suitable for Mach 03-04 stall suppression (based on CFD) will also be effective at lower Mach numbers
31 citations
TL;DR: In this article, the authors performed experimental and computational studies to obtain a fundamental understanding of the physics behind the lift and thrust production of a cycloidal rotor (cyclorotor) in forward flight for a unique blade pitching kinematics.
Abstract: This paper describes the systematic experimental and computational studies performed to obtain a fundamental understanding of the physics behind the lift and thrust production of a cycloidal rotor (cyclorotor) in forward flight for a unique blade pitching kinematics. The flow curvature effect (virtual camber and incidence due to the curvilinear flow) was identified to be a key factor affecting the lift, thrust, and power of the cyclorotor in forward flight. The experimental study involved systematic testing of a micro air vehicle-scale cyclorotor in an open-jet wind tunnel using a custom built three-component balance. The key parameters varied include rotor chord/radius ratio and blade pitching axis location because these two parameters have a strong impact on flow curvature effects. Because of the virtual camber/incidence effects and the differences in the aerodynamic velocities around the azimuth, the blades produce a small downward lift when they operate in the upper half of the circular trajectory and...
27 citations
TL;DR: A multifidelity optimization technique is applied to the design of a helicopter rotor blade to improve its performance in forward flight and it is shown that the blade can be improved in both longitudinal and forward flight.
Abstract: A multifidelity optimization technique is applied to the design of a helicopter rotor blade to improve its performance in forward flight. This optimization technique is based on a surrogate model t...
21 citations
TL;DR: In this article, a reduced-order model (ROM) is proposed to describe the linearized unsteady aerodynamics of helicopter rotors in arbitrary steady flight, which is particularly suited for the derivation of the state-space perturbation aeroelastic operators and is hence useful for stability analysis and aeroservoelastic applications.
Abstract: Reduced-order aerodynamic models are tools that may be conveniently applied in a wide range of research and design applications in the aeronautical and mechanical fields. This paper presents a methodology for the identification of a reduced-order model (ROM) describing the linearized unsteady aerodynamics of helicopter rotors in arbitrary steady flight, which is particularly suited for the derivation of the state-space perturbation aeroelastic operators and is hence useful for stability analysis and aeroservoelastic applications. It is defined in terms of multiblade coordinates and yields a (finite state) constant-coefficient, linear, differential form relating them to the corresponding multiblade aerodynamic loads. This approach requires the prediction of a set of harmonic perturbation responses by an aerodynamic solver. The accuracy of the identified ROM in describing unsteady aerodynamics phenomena is strictly connected to that of the aerodynamic solver. Complex aerodynamic effects (like wake roll-up and wake―blade interactions) are included in the ROM if they are taken into account in evaluating the harmonic responses. Numerical results concerning a flap-lag helicopter rotor in forward flight are presented. These examine the accuracy the aerodynamic ROM introduced both in terms of aerodynamic loads predictions and in terms of aeroelastic stability analysis. An aeroservoelastic application is also included in order to demonstrate the suitability of the ROM proposed for the design of controllers.
18 citations
TL;DR: In this paper, high-speed wind-tunnel experiments were conducted on a pitching airfoil equipped with an array of combustion-powered actuators, and the main objective of these experiments was to demonst...
Abstract: This work documents high-speed wind-tunnel experiments conducted on a pitching airfoil equipped with an array of combustion-powered actuators. The main objective of these experiments was to demonst...
16 citations