The Experts below are selected from a list of 2901 Experts worldwide ranked by ideXlab platform

Thomas F Brooks - One of the best experts on this subject based on the ideXlab platform.

  • HART-II: Prediction of Blade-Vortex Interaction Loading
    2003
    Co-Authors: Joon W. Lim, Casey L. Burley, D. D. Boyd, Berend G. Van Der Wall, Oliver Schneider, Aeroflightdynamics Directorate, Yung H. Yu, Chee Tung, Thomas F Brooks, Deutsches Zentrum
    Abstract:

    During the HART-I data analysis, the need for comprehensive wake data was found including Vortex creation and aging, and its re-development after Blade-Vortex Interaction. In October 2001, US Army AFDD, NASA Langley, German DLR, French ONERA and Dutch DNW performed the HART-II test as an international joint effort. The main objective was to focus on rotor wake measurement using a PIV technique along with the comprehensive data of Blade deflections, airloads, and acoustics. Three prediction teams made preliminary correlation efforts with HART-II data: a joint US team of US Army AFDD and NASA Langley, German DLR, and French ONERA. The predicted results showed significant improvements over the HART-I predicted results, computed about several years ago, which indicated that there has been better understanding of complicated wake modeling in the comprehensive rotorcraft analysis. All three teams demonstrated satisfactory prediction capabilities, in general, though there were slight deviations of prediction accuracies for various disciplines.

  • reduction of helicopter Blade Vortex Interaction noise by active rotor control technology
    Progress in Aerospace Sciences, 1997
    Co-Authors: Yung H. Yu, Bernd Gmelin, W R Splettstoesser, Jean Jacques Philippe, Jean Prieur, Thomas F Brooks
    Abstract:

    Abstract Helicopter Blade-Vortex Interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor Blade-Vortex Interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently available for rotor Blade-Vortex Interaction noise reduction, including higher harmonic pitch control, individual Blade control, and on-Blade control technologies. Basic physical mechanisms of each active control technique are reviewed in terms of noise reduction mechanism and controlling aerodynamic or structural parameters of a Blade. Active rotor control techniques using smart structures/materials are discussed, including distributed smart actuators to induce local torsional or flapping deformations.

  • reduction of helicopter Blade Vortex Interaction noise by active rotor control technology
    Progress in Aerospace Sciences, 1997
    Co-Authors: Bernd Gmelin, W R Splettstoesser, Jean Prieur, Philippe Jean Jacques, Thomas F Brooks
    Abstract:

    Helicopter Blade-Vortex Interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor Blade-Vortex Interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently available for rotor Blade Vortex Interaction noise reduction, including higher harmonic pitch control, individual Blade control, and on-Blade control technologies. Basic physical mechanisms of each active control technique are reviewed in terms of noise reduction mechanism and controlling aerodynamic or structural parameters of a Blade. Active rotor control techniques using smart structures/materials are discussed, including distributed smart actuators to induce local torsional or flapping deformations, Published by Elsevier Science Ltd.

  • Prediction and Measurement of Blade-Vortex Interaction Loading,
    1995
    Co-Authors: Chee Tung, Thomas F Brooks, Judith M. Gallman, Roland Kube, Gilles Rahier
    Abstract:

    Abstract : An extensive quantity of airload measurements was obtained for a pressure-instrumented model of the BO-105 main rotor for a large number of higher-harmonic control (HHC) settings at Duits-Nederlandse Wind Tunnel (DNW). The wake geometry, Vortex strength, and Vortex core size were also measured through a laser light sheet technique and LDV. These results are used to verify the BVI airload prediction methodologies developed by AFDD, DLR, NASA Langley, and ONERA. The comparisons show that an accurate prediction of the Blade motion and the wake geometry is the most important aspect of the BVI airload predictions. (AN)

  • analysis of a higher harmonic control test to reduce Blade Vortex Interaction noise
    Journal of Aircraft, 1994
    Co-Authors: Thomas F Brooks, Roland Kube, W R Splettstoesser, Earl R Booth, Klaus J Schultz, Douglas D Boyd, Georg Niesl, Olivier Streby
    Abstract:

    A noise study using an aeroelastically scaled BO-105 rotor was conducted in the German-Dutch Wind Tunnel to examine the use of higher harmonic control (HHC) of Blade pitch to reduce impulsive Blade-Vortex Interaction (BVI) noise. The noise directivity was measured over a large plane underneath the rotor using a traversing inflow microphone array. Noise and vibration measurements were made for a range of matched rotor operating conditions where prescribed (or open loop) HHC pitch, at various amplitudes and phases, was superimposed on normal (baseline) collective and cyclic trim pitch. Acoustic data are presented for 3, 4, and 5P HHC applied to a typical landing approach rotor operating condition where BVI noise is normally intense. Noise reductions of up to 6 dB were found for the advancing side BVI noise radiating upstream of the rotor, and also for the retreating side BVI noise radiating below and downstream of the rotor. The relative levels between the sides were modified by HHC control phase. To help give insight to the physics of the HHC/BVI noise problem, highresolution loading and noise prediction results are presented for comparison to the data. The predictions are based on a new high-resolution version of the CAMRAD rotor performance program under development at Langley, called HIRES.

Bernd Gmelin - One of the best experts on this subject based on the ideXlab platform.

  • reduction of helicopter Blade Vortex Interaction noise by active rotor control technology
    Progress in Aerospace Sciences, 1997
    Co-Authors: Yung H. Yu, Bernd Gmelin, W R Splettstoesser, Jean Jacques Philippe, Jean Prieur, Thomas F Brooks
    Abstract:

    Abstract Helicopter Blade-Vortex Interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor Blade-Vortex Interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently available for rotor Blade-Vortex Interaction noise reduction, including higher harmonic pitch control, individual Blade control, and on-Blade control technologies. Basic physical mechanisms of each active control technique are reviewed in terms of noise reduction mechanism and controlling aerodynamic or structural parameters of a Blade. Active rotor control techniques using smart structures/materials are discussed, including distributed smart actuators to induce local torsional or flapping deformations.

  • reduction of helicopter Blade Vortex Interaction noise by active rotor control technology
    Progress in Aerospace Sciences, 1997
    Co-Authors: Bernd Gmelin, W R Splettstoesser, Jean Prieur, Philippe Jean Jacques, Thomas F Brooks
    Abstract:

    Helicopter Blade-Vortex Interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor Blade-Vortex Interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently available for rotor Blade Vortex Interaction noise reduction, including higher harmonic pitch control, individual Blade control, and on-Blade control technologies. Basic physical mechanisms of each active control technique are reviewed in terms of noise reduction mechanism and controlling aerodynamic or structural parameters of a Blade. Active rotor control techniques using smart structures/materials are discussed, including distributed smart actuators to induce local torsional or flapping deformations, Published by Elsevier Science Ltd.

W R Splettstoesser - One of the best experts on this subject based on the ideXlab platform.

  • reduction of helicopter Blade Vortex Interaction noise by active rotor control technology
    Progress in Aerospace Sciences, 1997
    Co-Authors: Yung H. Yu, Bernd Gmelin, W R Splettstoesser, Jean Jacques Philippe, Jean Prieur, Thomas F Brooks
    Abstract:

    Abstract Helicopter Blade-Vortex Interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor Blade-Vortex Interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently available for rotor Blade-Vortex Interaction noise reduction, including higher harmonic pitch control, individual Blade control, and on-Blade control technologies. Basic physical mechanisms of each active control technique are reviewed in terms of noise reduction mechanism and controlling aerodynamic or structural parameters of a Blade. Active rotor control techniques using smart structures/materials are discussed, including distributed smart actuators to induce local torsional or flapping deformations.

  • reduction of helicopter Blade Vortex Interaction noise by active rotor control technology
    Progress in Aerospace Sciences, 1997
    Co-Authors: Bernd Gmelin, W R Splettstoesser, Jean Prieur, Philippe Jean Jacques, Thomas F Brooks
    Abstract:

    Helicopter Blade-Vortex Interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor Blade-Vortex Interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently available for rotor Blade Vortex Interaction noise reduction, including higher harmonic pitch control, individual Blade control, and on-Blade control technologies. Basic physical mechanisms of each active control technique are reviewed in terms of noise reduction mechanism and controlling aerodynamic or structural parameters of a Blade. Active rotor control techniques using smart structures/materials are discussed, including distributed smart actuators to induce local torsional or flapping deformations, Published by Elsevier Science Ltd.

  • analysis of a higher harmonic control test to reduce Blade Vortex Interaction noise
    Journal of Aircraft, 1994
    Co-Authors: Thomas F Brooks, Roland Kube, W R Splettstoesser, Earl R Booth, Klaus J Schultz, Douglas D Boyd, Georg Niesl, Olivier Streby
    Abstract:

    A noise study using an aeroelastically scaled BO-105 rotor was conducted in the German-Dutch Wind Tunnel to examine the use of higher harmonic control (HHC) of Blade pitch to reduce impulsive Blade-Vortex Interaction (BVI) noise. The noise directivity was measured over a large plane underneath the rotor using a traversing inflow microphone array. Noise and vibration measurements were made for a range of matched rotor operating conditions where prescribed (or open loop) HHC pitch, at various amplitudes and phases, was superimposed on normal (baseline) collective and cyclic trim pitch. Acoustic data are presented for 3, 4, and 5P HHC applied to a typical landing approach rotor operating condition where BVI noise is normally intense. Noise reductions of up to 6 dB were found for the advancing side BVI noise radiating upstream of the rotor, and also for the retreating side BVI noise radiating below and downstream of the rotor. The relative levels between the sides were modified by HHC control phase. To help give insight to the physics of the HHC/BVI noise problem, highresolution loading and noise prediction results are presented for comparison to the data. The predictions are based on a new high-resolution version of the CAMRAD rotor performance program under development at Langley, called HIRES.

Massimo Gennaretti - One of the best experts on this subject based on the ideXlab platform.

  • rotorcraft comprehensive code assessment for Blade Vortex Interaction conditions
    Aerospace Science and Technology, 2018
    Co-Authors: Massimo Gennaretti, Giovanni Bernardini, Jacopo Serafini, Gianluca Romani
    Abstract:

    Abstract The scope of this paper is the presentation of the computational methodologies applied in the comprehensive code for rotorcraft developed in the last years at Roma Tre University, along with the assessment of its prediction capabilities focused on flight conditions characterized by strong Blade–Vortex Interactions. Boundary element method approaches are applied for both potential aerodynamics and aeroacoustics solutions, whereas a harmonic-balance/modal approach is used to integrate the rotor aeroelastic equations. The validation campaign of the comprehensive code has been carried out against the well-known HART II database, which is the outcome of a joint multi-national effort aimed at performing wind tunnel measurements of loads, Blade deflection, wake shape and noise concerning a four-Bladed model rotor in low-speed descent flight. Comparisons with numerical simulations available in the literature for the same test cases are also presented. It is shown that, with limited computational cost, the results provided by the Roma Tre aero-acousto-elastic solver are in good agreement with the experimental data, with a level of accuracy that is in line with the state-of-the-art predictions. The influence of the Vortex core modeling on aerodynamic predictions and the influence of the inclusion of the fuselage shielding effect on aeroacoustic predictions are discussed.

  • pressure feedback based Blade Vortex Interaction noise controller for helicopter rotors
    International Journal of Aeroacoustics, 2018
    Co-Authors: Sara Modini, Giovanni Bernardini, G Graziani, Massimo Gennaretti
    Abstract:

    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 ...

  • synthesis of active twist controller for rotor Blade Vortex Interaction noise alleviation
    Journal of Aircraft, 2016
    Co-Authors: Alessandro Anobile, Massimo Gennaretti, Giovanni Bernardini, Claudio Testa
    Abstract:

    This paper deals with an efficient computational process for the synthesis of a low-frequency controller aimed at alleviating helicopter rotor Blade–Vortex Interaction noise. It is based on an optimal, multicyclic, control approach that exploits distributed torque loads actuated by smart materials to twist rotor Blades at the 2/rev frequency (active twist rotor concept). Aeroacoustic rotor simulations are based on aerodynamic and aeroelastic tools capable of accurately predicting wake–Blade miss distance, which plays a crucial role in Blade–Vortex Interaction noise emission. Its modification is the main objective of the proposed controller action. The control law is identified through a numerically efficient aeroacoustic solver based on analytical–numerical sectional aerodynamics modeling. Numerical investigations first examine noise emission sensitivity to active twist actuation, then identify control and output variables suitable for the closed-loop controller. Finally effectiveness of the proposed low-...

  • parallel Blade Vortex Interaction modelling for helicopter rotor noise control synthesis
    International Journal of Aeroacoustics, 2014
    Co-Authors: Sara Modini, Giovanni Bernardini, G Graziani, Massimo Gennaretti
    Abstract:

    The present work deals with a methodology for the alleviation of loads and corresponding emitted noise generated by Blade-Vortex Interaction (BVI) phenomena occurring on helicopter main rotors in low-speed, descent flight. It consists of a multi-cyclic, optimal control approach driving higher harmonic Blade pitch actuation. First, for the specific flight condition to be examined, the BVI phenomena are simulated as equivalent two-dimensional, multi-Vortex, parallel BVI problems and then a local controller methodology is applied for the efficient identification of the closed-loop control algorithm. In order to assess the capability of the proposed control approach to alleviate rotor Blade loads and emitted noise, the results of a numerical investigation concerning a realistic helicopter main rotor in descent flight are presented and discussed.

  • synthesis of a rotor noise controller by parallel Blade Vortex Interaction aeroelastic modelling
    8th International Symposium on FLUID-­‐STRUCTURE INTERACTIONS FLOW-­SOUND INTERACTIONS & FLOW-­INDUCED VIBRATION & NOISE, 2014
    Co-Authors: Sara Modini, Giovanni Bernardini, G Graziani, Massimo Gennaretti
    Abstract:

    The aim of this paper is the presentation and application of a methodology for the identification of a multi-cyclic, higher harmonic Blade pitch actuation controller suited for alleviating impulsive noise induced by Blade-Vortex Interactions (BVI). The Blade pitch actuation is driven by a feedback control law derived by an optimal linear-quadratic regulator control formulation based on simulations provided by an equivalent two-dimensional, multi-Vortex, parallel BVI problem that describes the aerodynamic response of elastic rotor Blade cross sections in BVI conditions. This control law identification process is particularly efficient in that exploits two-dimensional simulations, instead of using three-dimensional, time-consuming predictions. In order to examine the effectiveness of the proposed controller in alleviating BVI noise, it is applied to the analysis of a realistic helicopter main rotor in descent flight.Copyright © 2014 by ASME

Marcel Ilie - One of the best experts on this subject based on the ideXlab platform.

  • a fully coupled cfd csd computational approach for aeroelastic studies of helicopter Blade Vortex Interaction
    Applied Mathematics and Computation, 2019
    Co-Authors: Marcel Ilie
    Abstract:

    Abstract Blade-Vortex Interaction (BVI) is one of the main sources of noise and vibrations in helicopters. The aeroelastic response of the Blade, to BVI phenomenon, is one of the main factors affecting the helicopter's aerodynamic performance and stability. In the present research we developed and implemented a novel CFD-based, strong (two-way) time-domain coupling, mathematical model, for the numerical prediction of the aeroelastic response of the helicopter Blade to BVI. Another novelty, of the fully coupled CFD/CSD approach, is that the fluid flow is solved using the large-eddy simulation (LES) approach. In the present research, the aeroelastic response of a symmetric NACA0012 airfoil to BVI is computed using a two-degree of freedom (2-DOF) mass/spring model. The numerical studies show that the Blade-Vortex offset distance, (h), plays a key role in the mechanism of BVI and therefore, it influences the aerodynamic coefficients. The computational studies show that the BVI phenomenon diminishes with the increase of the offset distance (h). Also, it was observed that the elastic nature of the airfoil acts as a damper and it diminishes the effect of BVI on the aerodynamic coefficients. Therefore, for a flexible airfoil, the lift coefficient exhibits a decay, at the instant of Blade-Vortex Interaction, when compared with rigid airfoil.

  • numerical study of helicopter Blade Vortex mechanism of Interaction using the potential flow theory
    Applied Mathematical Modelling, 2012
    Co-Authors: Patricia X. Coronado Domenge, Marcel Ilie
    Abstract:

    Abstract The Blade–Vortex Interaction (BVI) phenomenon plays a key role in the rotorcraft aerodynamics. Numerical investigations of BVI using classical CFD approaches are computationally expensive. In the present research we propose a numerical approach, based on the potential flow theory, for the numerical investigation of helicopter Blade–Vortex mechanism of Interaction. This approach overcomes the computational expenses posed by the CFD techniques. The influence of vertical miss distance, angle of attack, airfoil camber, and Vortex strength on the helicopter Blade–Vortex mechanism of Interaction is subject of investigation. The study reveals that the magnitude of the aerodynamic coefficients decreases with the increase of vertical miss distance and angle of attack, and the decrease of Vortex strength and core size.

  • a novel concept towards the reduction of helicopter Blade Vortex Interaction a numerical study using large eddy simulation
    19th AIAA Computational Fluid Dynamics, 2009
    Co-Authors: Marcel Ilie
    Abstract:

    A novel technique regarding the reduction of the influence of helicopter Blade-Vortex Interaction on the aerodynamic coefficients is proposed. The proposed technique is based on the idea of injecting air at the leading edge of the Blade to alter the characteristics of the Vortex. The numerical investigations are performed using the large-eddy simulation (LES) approach. The simulations were performed for a Reynolds number, Re = 1.3 x 10 6 , based on the NACA0012 airfoil chord and free-stream velocity. The present study shows that using the leading edge air mass injection (LEAMI) concept, the influence of Blade-Vortex Interaction on the aerodynamic coefficients is significantly reduced.

  • critical aerodynamic aspects of helicopter Blade Vortex Interaction a numerical study using large eddy simulation
    27th AIAA Applied Aerodynamics Conference, 2009
    Co-Authors: Marcel Ilie, Stephan Llewellyn Smith
    Abstract:

    Numerical investigations of helicopter Blade-Vortex mechanism of Interaction are performed using large eddy simulation (LES). The simulations were performed for a Reynolds number, Re = 1.3 x 10, based on the chord, c, of the airfoil (NACA0012). Computations are carried out for two different types of Blade-Vortex Interactions, concerning single and respectively two vortices Blade Interaction. It was observed that for single Vortex-Blade Interaction, the Blade-Vortex Interaction becomes less significant with the increase of vertical miss distance. Larger amplitudes of aerodynamic coefficients were observed for the case of two vortices-Blade Interaction when compared with the single Vortex Blade Interactions.

  • reduction of bvi noise using a leading edge air mass injection concept a numerical study using large eddy simulation
    AIAA CEAS Aeroacoustics Conference, 2009
    Co-Authors: Marcel Ilie
    Abstract:

    A novel technique regarding the reduction of helicopter Blade-Vortex Interaction noise is proposed. The proposed technique is based on the idea of injecting air at the leading edge of the Blade to alter the Vortex characteristics (strength and core size). The numerical investigations are performed using the large-eddy simulation (LES) approach. The simulations were performed for a Reynolds number, Re = 1.3 x 10 6 , based on the NACA0012 airfoil chord and free-stream velocity. The present study shows that by injecting air at the leading edge of the Blade, the influence of Blade-Vortex Interaction on the aerodynamic coefficients and aeroacoustic noise is significantly reduced.