Fundamental investigation using active plasma control to reduce blade–vortex interaction noise

2021 ◽  
pp. 1475472X2110526
Author(s):  
Trushant K Patel ◽  
Alexander J Lilley ◽  
Weiqi Shen ◽  
Christian Porrello ◽  
Alexander Schindler-Tyka ◽  
...  
Keyword(s):  
Rotor Blades ◽  
Tip Vortex ◽  
Plasma Actuators ◽  
Supporting Evidence ◽  
Vortex Interaction ◽  
Dominant Component ◽  
Fundamental Investigation ◽  
Blade Vortex Interaction ◽  
Aerial Vehicle ◽  
Blade Tip

Blade vortex interaction noise is a problematic and dominant component of rotor noise. Plasma actuators strategically placed at the tip of the rotor blades can reduce the strength of the tip vortices. This reduction has the potential to significantly reduce blade vortex interaction noise. A combined experimental, numerical, and theoretical program shows supporting evidence that low power plasma actuators can effectively lower coherence of the blade tip vortex and reduce blade vortex interaction noise over-pressure by up to 80%. For a nominal small five-bladed unmanned aerial vehicle, we predict an approximate 8.88 maximum ΔdB reduction for a 150 m/s tip speed. Experimental, computational, and acoustic modeling support these predictions. This study represents a fundamental investigation in the fixed-frame, which provides evidence for higher level research and testing in a rotating framework.

Prediction of Blade-Vortex Interaction Airloads With Higher-Harmonic Pitch Controls Using the 2GCHAS Comprehensive Code

2001 ◽  
Vol 123 (4) ◽  
pp. 469-474 ◽  
Author(s):  
Joon W. Lim ◽  
Chee Tung ◽  
Yung H. Yu
Keyword(s):  
Tip Vortex ◽  
Vortex Interaction ◽  
Main Rotor ◽  
Scaled Model ◽  
Harmonic Control ◽  
Blade Vortex Interaction ◽  
Higher Harmonic Control ◽  
Blade Tip ◽  
Higher Harmonic ◽  
Analysis System

Analytically predicted results of blade-vortex interaction (BVI) airloads, using the second- generation comprehensive helicopter analysis system (2GCHAS), are presented with the experimental results obtained from the higher-harmonic-control aeroacoustic rotor test (HART) program using a 40-percent, Mach-scaled model of the hingeless BO-105 main rotor. Correlations include airloads, blade tip deflections, and tip vortex geometry. The effects on blade airload predictions are studied with higher-harmonic pitch controls (HHC). It was concluded that the blade torsional deflection and the wake system play a very important role in predicting BVI airloads.

Pressure feedback-based blade–vortex interaction noise controller for helicopter rotors

2018 ◽  
Vol 17 (3) ◽  
pp. 295-318 ◽  
Author(s):  
Sara Modini ◽  
Giorgio Graziani ◽  
Giovanni Bernardini ◽  
Massimo Gennaretti
Keyword(s):  
High Harmonic ◽  
Three Dimensional ◽  
Rotor Blades ◽  
Aerodynamic Noise ◽  
Vortex Interaction ◽  
Noise Sources ◽  
Power Requirement ◽  
Blade Vortex Interaction ◽  
Pressure Feedback ◽  
Helicopter Main Rotor

With the aim of alleviating the noise annoyance emitted by blade–vortex interactions occurring on helicopter main rotors, the present work presents a methodology suitable for the identification of a multi-cyclic harmonic controller based on the actuation of rotor blades equipped with Miniature Trailing Edge Effectors. The objective of the control methodology is the direct suppression of the aerodynamic noise sources by generation of localized high-harmonic blade–vortex interaction counter-actions. The set-up of control devices is selected on the basis of the blade–vortex interaction scenario, taking into account a trade-off between effectiveness and power requirement. The control law is efficiently identified by means of an optimal controller synthesized through suitable two-dimensional multi-vortex, parallel blade–vortex interaction problems. The proposed methodology is validated by the application to realistic helicopter main rotors during low-speed descent flights, numerically simulated through high-fidelity aerodynamic and aeroacoustic solvers based, respectively, upon a three-dimensional free-wake boundary element method to solve the potential flow around rotors in blade–vortex interaction conditions and the Farassat 1A formulation. Results concerning the capability of the proposed controller to alleviate the blade–vortex interaction noise emitted by a realistic helicopter main rotor are presented and discussed.

Computational aeroelastic analysis of slowed rotors at high advance ratios

2014 ◽  
Vol 118 (1201) ◽  
pp. 297-313 ◽  
Author(s):  
J. de Montaudouin ◽  
N. Reveles ◽  
M. J. Smith
Keyword(s):  
High Speed ◽  
Rotor Blades ◽  
Vortex Interaction ◽  
Blade Loading ◽  
Blade Vortex Interaction ◽  
Aeroelastic Analysis ◽  
Computational Fluid Dynamics Cfd ◽  
Advance Ratio ◽  
Cfd Method ◽  
Model Rotor

Abstract The aerodynamic and aeroelastic behaviour of a rotor become more complex as advance ratios increase to achieve high-speed forward fight. As the rotor blades encounter large regions of cross and reverse flows during each revolution, strong variations in the local Mach regime are encountered, inducing complex elastic blade deformations. In addition, the wake system may remain in the vicinity of the rotor, adding complexity to the blade loading. The aeroelastic behaviour of a model rotor with advance ratios ranging from 0·5 to 2·0 has been evaluated with aerodynamics provided via a computational fluid dynamics (CFD) method. Significant radial blade-vortex interaction can occur at a high advance ratio; the advance ratio at which this occurs is dependent on the rotor configuration. This condition is accompanied by high vibratory loads, peak negative torsion, and peak torsion and in-plane loads. The high vibratory loading increases the sensitivity of the trim model, so that at some high advance ratios the vibratory loads must be filtered to achieve a trimmed state.

Blade tip vortex measurements on actively twisted rotor blades

2017 ◽  
Vol 58 (5) ◽  
Author(s):  
André Bauknecht ◽  
Benjamin Ewers ◽  
Oliver Schneider ◽  
Markus Raffel
Keyword(s):  
Rotor Blades ◽  
Tip Vortex ◽  
Blade Tip

scholarly journals Impact of Tip-Vortex Modeling Uncertainty on Helicopter Rotor Blade–Vortex Interaction Noise Prediction

2021 ◽  
Vol 66 (1) ◽  
pp. 1-13
Author(s):  
Stavros Vouros ◽  
Ioannis Goulos ◽  
Calum Scullion ◽  
Devaiah Nalianda ◽  
Vassilios Pachidis
Keyword(s):  
Vortex Core ◽  
Numerical Procedure ◽  
Tip Vortex ◽  
Analytical Models ◽  
Aerodynamic Noise ◽  
Helicopter Rotor ◽  
Vortex Interaction ◽  
Blade Vortex Interaction ◽  
Free Wake ◽  
The Impact

Free-wake models are routinely used in aeroacoustic analysis of helicopter rotors; however, their semiempiricism is accompanied with uncertainty related to the modeling of physical wake parameters. In some cases, analysts have to resort to empirical adaption of these parameters based on previous experimental evidence. This paper investigates the impact of inherent uncertainty in wake aerodynamic modeling on the robustness of helicopter rotor aeroacoustic analysis. A free-wake aeroelastic rotor model is employed to predict high-resolution unsteady airloads, including blade–vortex interactions. A rotor aeroacoustics model, based on integral solutions of the Ffowcs Williams–Hawkings equation, is utilized to calculate aerodynamic noise in the time domain. The individual analytical models are incorporated into an uncertainty analysis numerical procedure, implemented through nonintrusive Polynomial Chaos expansion. The potential sources of uncertainty in wake tip-vortex core growth modeling are identified and their impact on noise predictions is systematically quantified. When experimental data to adjust the tip-vortex core model are not available the uncertainty in acoustic pressure and noise impact at observers dominated by blade–vortex interaction noise can reach up to 25% and 3.50 dB, respectively. A set of generalized uncertainty maps is derived, for use as modeling guidelines for aeroacoustic analysis in the absence of the robust evidence necessary for calibration of semiempirical vortex core models.

WALL-BOUNDED BLADE-TIP VORTEX INTERACTION NOISE

1997 ◽  
Vol 202 (5) ◽  
pp. 605-618 ◽  
Author(s):  
R.C. Dunne ◽  
M.S Howe
Keyword(s):  
Tip Vortex ◽  
Vortex Interaction ◽  
Blade Tip

A wind-tunnel based study of helicopter tail rotor blade vortex interaction

2004 ◽  
Vol 108 (1083) ◽  
pp. 237-244 ◽  
Author(s):  
F. N. Coton ◽  
R. A. McD. Galbraith ◽  
T. Wang ◽  
S. J. Newman
Keyword(s):  
Wind Tunnel ◽  
Rotor Blade ◽  
Tip Vortex ◽  
Vortex Interaction ◽  
Pressure Transducers ◽  
Control Effectiveness ◽  
Rotating Blade ◽  
Blade Vortex Interaction ◽  
Bladed Rotor ◽  
Development And Validation

AbstractThe interaction of a helicopter tail rotor blade with the tip vortex system from the main rotor is a significant source of noise and, in some flight states, can produce marked reductions in control effectiveness. This paper describes a series of wind-tunnel tests to simulate tail rotor blade vortex interaction with a view to providing data for the development and validation of numerical simulations of the phenomenon. In the experiments, which were carried out in the Argyll wind-tunnel of Glasgow University, a single-bladed rotor located in the tunnel’s contraction was used to generate the tip vortex which travelled downstream into the working section where it interacted with a model tail rotor. The tail rotor was instrumented with miniature pressure transducers that measured the aerodynamic response during the interaction. The results suggest that the rotor blade vortex interaction is similar in form to that measured at much higher spatial resolution on a fixed, non-rotating blade. The combination of the two datasets, therefore, provides a valuable resource for the development and validation of predictive schemes.

Investigating the Coupled Effects Between Rotor-Blade Aeroelasticity and Tip Vortex Stability

2020 ◽  
Author(s):  
Steven N. Rodriguez ◽  
Athanasios P. Iliopoulos ◽  
John G. Michopoulos ◽  
Justin W. Jaworski
Keyword(s):  
Rotor Blade ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Tip Vortex ◽  
Tip Vortices ◽  
Operational Conditions ◽  
Vortex Stability ◽  
Blade Vortex Interaction ◽  
Wake Interactions ◽  
The Relationship

Abstract The relationship between rotor-blade aeroelasticity and tip-vortex stability is investigated numerically. An aeroelastic framework based on the free-vortex wake and finite element methods is employed to model a subscaled helicopter rotor in hover and forward-tilted conditions. A linear eigenvalue stability analysis is performed on tip vortices to associate the coupled impact of aeroelastic effects and vortex evolution. Prior numerical investigations have shown that highly flexible wind turbine rotor-blades have the potential to decrease levels of the instability of tip vortices. The present work focuses on testing these findings against a subscaled rotor within the range of helicopter operational rotation frequencies. The presented work aims to develop further insight into rotor-wake interactions and blade-vortex interaction to explore the mitigation of adverse rotorcraft operational conditions, such as their effect on aerodynamic-induced airframe vibrations and the associated life-cycle fatigue performance.

Rotating Instabilities in an Axial Compressor Originating From the Fluctuating Blade Tip Vortex

2000 ◽  
Author(s):  
R. Mailach ◽  
I. Lehmann ◽  
K. Vogeler
Keyword(s):  
Rotor Blade ◽  
Laser Doppler Anemometry ◽  
Stability Limit ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Experimental Investigations ◽  
Flow Phenomenon ◽  
Low Speed ◽  
Blade Tip

Rotating instabilities (RI) have been observed in axial flow fans, centrifugal compressors as well as in low-speed and high-speed axial compressors. They are responsible for the excitation of high amplitude rotor blade vibrations and noise generation. This flow phenomenon moves relative to the rotor blades and causes periodic vortex separations at the blade tips and an axial reversed flow through the tip clearance of the rotor blades. The paper describes experimental investigations of RI in the Dresden Low-Speed Research Compressor (LSRC). The objective is to show that the fluctuation of the blade tip vortex is responsible for the origination of this flow phenomenon. RI have been found at operating points near the stability limit of the compressor with relatively large tip clearance of the rotor blades. The application of time-resolving sensors in both fixed and rotating frame of reference enables a detailed description of the circumferential structure and the spatial development of this unsteady flow phenomenon, which is limited to the blade tip region. Laser-Doppler-Anemometry (LDA) within the rotor blade passages and within the tip clearance as well as unsteady pressure measurements on the rotor blades show the structure of the blade tip vortex. It will be shown that the periodical interaction of the blade tip vortex of one blade with the flow at the adjacent blade is responsible for the generation of a rotating structure with high mode orders, termed as rotating instability (RI).

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