Author: Romuald MorvantPublisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 199
Book Description
The Investigation of Blade-vortex Interaction Noise Using Computational Fluid Dynamics
Author: Romuald MorvantPublisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 199
Book Description
Helicopter Blade-Vortex Interaction Noise with Comparisons to Cfd Calculations
Author: National Aeronautics and Space Administration (NASA)Publisher: Createspace Independent Publishing Platform
ISBN: 9781722428778
Category :
Languages : en
Pages : 60
Book Description
A comparison of experimental acoustics data and computational predictions was performed for a helicopter rotor blade interacting with a parallel vortex. The experiment was designed to examine the aerodynamics and acoustics of parallel Blade-Vortex Interaction (BVI) and was performed in the Ames Research Center (ARC) 80- by 120-Foot Subsonic Wind Tunnel. An independently generated vortex interacted with a small-scale, nonlifting helicopter rotor at the 180 deg azimuth angle to create the interaction in a controlled environment. Computational Fluid Dynamics (CFD) was used to calculate near-field pressure time histories. The CFD code, called Transonic Unsteady Rotor Navier-Stokes (TURNS), was used to make comparisons with the acoustic pressure measurement at two microphone locations and several test conditions. The test conditions examined included hover tip Mach numbers of 0.6 and 0.7, advance ratio of 0.2, positive and negative vortex rotation, and the vortex passing above and below the rotor blade by 0.25 rotor chords. The results show that the CFD qualitatively predicts the acoustic characteristics very well, but quantitatively overpredicts the peak-to-peak sound pressure level by 15 percent in most cases. There also exists a discrepancy in the phasing (about 4 deg) of the BVI event in some cases. Additional calculations were performed to examine the effects of vortex strength, thickness, time accuracy, and directionality. This study validates the TURNS code for prediction of near-field acoustic pressures of controlled parallel BVI. McCluer, Megan S. Ames Research Center...
Computational Investigation of Blade Vortex Interaction Noise
Author: See-Ho WongNew Computational Methods for the Prediction and Analysis of Helicopter Noise
Author: Roger C. StrawnPublisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 18
Book Description
Abstract: "This paper describes several new methods to predict and analyze rotorcraft noise. These methods are: 1) a combined computational fluid dynamics and Kirchhoff scheme for far-field noise predictions, 2) parallel computer implementation of the Kirchhoff integrations, 3) audio and visual rendering of the computed acoustic predictions over large far-field regions, and 4) acoustic tracebacks to the Kirchhoff surface to pinpoint the sources of the rotor noise. The paper describes each method and presents sample results for three test cases. The first case consists of in-plane high-speed impulsive noise and the other two cases show idealized parallel and oblique blade-vortex interactions. The computed results show good agreement with available experimental data but convey much more information about the far-field noise propagation. When taken together, these new analysis methods exploit the power of new computer technologies and offer the potential to significantly improve our prediction and understanding of rotorcraft noise."
Full-Potential Modeling of Blade-Vortex Interactions
Author: Henry E. JonesPublisher:
ISBN:
Category : Unsteady flow (Aerodynamics)
Languages : en
Pages : 96
Book Description
A study of the full-potential modeling of a blade-vortex interaction was made. A primary goal of this study was to investigate the effectiveness of the various methods of modeling the vortex. The model problem restricts the interaction to that of an infinite wing with an infinite line vortex moving parallel to its leading edge. This problem provides a convenient testing ground for the various methods of modeling the vortex while retaining the essential physics of the full three-dimensional interaction. A full-potential algorithm specifically tailored to solve the blade-vortex interaction (BVI) was developed to solve this problem. The basic algorithm was modified to include the effect of a vortex passing near the airfoil. Four different methods of modeling the vortex were used: (1) the angle-of-attack methods, (2) the lifting-surface method, (3) the branch-cut method, and (4) the split-potential method. A side-by-side comparison of the four models was conducted. these comparisons included comparing generated velocity fields, a subcritical interaction, and a critical interaction. The subcritical and critical interactions are compared with experimentally generate results. The split-potential model was used to make a survey of some of the more critical parameters which affect the BVI.
Investigation of the Orthogonal Blade-Vortex Interaction
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 44
Book Description
A Stereoscopic Particle Image Velocimetry (SPIV) system was developed and applied to measurements of the Orthogonal Blade-Vortex Interaction (BVI) in a wind tunnel. Measurements of the isolated vortex showed that the SPIV system could resolve the jet velocity profile within the vortex core to a reasonable accuracy, and views of the vortex from different sides of the wind tunnel showed similar velocity profiles. For the BVI measurements the SPIV system showed the existence of a strong.
Frontiers of Computational Fluid Dynamics 2006
Author: David A. CaugheyPublisher: World Scientific
ISBN: 9812703187
Category : Mathematics
Languages : en
Pages : 466
Book Description
The series of volumes to which this book belongs honors contributors who have made a major impact in computational fluid dynamics. This fourth volume in the series is dedicated to David Caughey on the occasion of his 60th birthday. The first volume was published in 1994 and was dedicated to Prof Antony Jameson. The second, dedicated to Earl Murman, was published in 1998. The third volume was dedicated to Robert MacCormack in 2002. Written by leading researchers from academia, government laboratories, and industry, the contributions in this volume present descriptions of the latest developments in techniques for numerical analysis of fluid flow problems, as well as applications to important problems in industry.
An Overset Grid Navier-Stokes/Kirchhoff-surface Method for Rotorcraft Aeroacoustic Predictions
Author: Earl P. N. DuquePublisher:
ISBN:
Category : Navier-Stokes equations
Languages : en
Pages : 20
Book Description
Abstract: "This paper describes a new method for computing the flowfield and acoustic signature of arbitrary rotors in forward flight. The overall scheme uses a finite-difference Navier-Stokes solver to compute the aerodynamic flowfield near the rotor blades. The equations are solved on a system of overset grids that allow for prescribed cyclic and flapping blade motions and capture the interactions between the rotor blades and wake. The far-field noise is computed with a Kirchhoff integration over a surface that completely encloses the rotor blades. Flowfield data are interpolated onto this Kirchhoff surface using the same overset-grid techniques that are used for the flowfield solution. As a demonstration of the overall prediction scheme, computed results for far-field noise are compared with experimental data for both high-speed impulsive (HSI) and blade-vortex interaction (BVI) cases. The HSI case showed good agreement with experimental data while a preliminary attempt at the BVI case did not. The computations clearly show that temporal accuracy, spatial accuracy and grid resolution in the Navier-Stokes solver play key roles in the overall accuracy of the predicted noise. These findings will be addressed more closely in future BVI computations. Overall, the overset-grid CFD scheme provides a powerful new framework for the prediction of helicopter noise."
Computational Study of High Speed Blade-vortex Interaction
Author: Erkan YildirimPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
This thesis presents inviscid compressible simulations for the orthogonal blade-vortex interaction. A numerical model between the tail rotor of a helicopter and the trailing vortex system formed by the main rotor blades is assumed. The study takes a 'building-block' approach to investigating this problem. Firstly, the impulsive instantaneous blocking of the axial core flow by a flat plate is considered. In the second step, the three-dimensional gradual cutting of the vortex by a sharp flat-plate that moves at a finite speed through the vortex is performed. Finally the chopping of the vortex by a blunt leading edge aerofoil, which incorporates both the blocking effect and also the stretching and distortion of the vortex lines is studied. The solutions reveal that the compressibility effects are strong when the axial core flow of the vortex is impulsively blocked. This generates a weak shock-expansion structure propagating along the vortex core on opposite sides of the cutting surface. The shock and expansion waves are identified as the prominent acoustic signatures in the interaction. In a simplified, two-dimensional axisymmetric model, the modelling of the physical evolution of the vortex, including the evolution of the complex vortical structures that controls the vortex core size near the cutting surface, are studied. Furthermore, the three dimensional simulations revealed that there is a secondary and a tertiary noise sources due to compressibility effects at the blade leading edge and due to the shock-vortex interaction taking place on the blade, which is exposed to a transonic free-stream flow.
Author: