Flow Field and Acoustics of Two-Dimensional Transonic Blade-Vortex Interactions PDF Download
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Author: A. R. George
Publisher:
ISBN:
Category :
Languages : en
Pages : 49
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Book Description
Blade-vortex interaction noise from full-scale helicopters is shown to involve unsteady transonic flow phenomena which can be modeled as two-dimensional. An unsteady, small-disturbance-theory, numerical analysis, is used to model the interaction of an airfoil with a finite-core, locally-convected vortex using the vortex-in-cell method with multiple branch cuts accounting for the distributed vortices' potential jumps. Strong disturbances propagating from the blade-vortex interaction are associated with occurrence of Tijdeman's Type C flow on the airfoil's lower surface. In this type of flow, the shock which initially terminates a supersonic zone propagates through it and forward off the airfoil. The effects of airfoil shape, angle of attack, Mach number, vortex strength, and vortex miss distance on the flow and on waves radiated forward are investigated. It is found that stronger radiated waves are associated with narrow supersonic regions and near-sonic base flow. Also, stronger vortices generate stronger radiated waves, but miss distance is not as important a factor. Originator-supplied keywords include: Acoustics, Noise(Sound), and Numerical analysis.
Author: A. R. George
Publisher:
ISBN:
Category :
Languages : en
Pages : 49
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Book Description
Blade-vortex interaction noise from full-scale helicopters is shown to involve unsteady transonic flow phenomena which can be modeled as two-dimensional. An unsteady, small-disturbance-theory, numerical analysis, is used to model the interaction of an airfoil with a finite-core, locally-convected vortex using the vortex-in-cell method with multiple branch cuts accounting for the distributed vortices' potential jumps. Strong disturbances propagating from the blade-vortex interaction are associated with occurrence of Tijdeman's Type C flow on the airfoil's lower surface. In this type of flow, the shock which initially terminates a supersonic zone propagates through it and forward off the airfoil. The effects of airfoil shape, angle of attack, Mach number, vortex strength, and vortex miss distance on the flow and on waves radiated forward are investigated. It is found that stronger radiated waves are associated with narrow supersonic regions and near-sonic base flow. Also, stronger vortices generate stronger radiated waves, but miss distance is not as important a factor. Originator-supplied keywords include: Acoustics, Noise(Sound), and Numerical analysis.
Author: Anastasios Sotirios Lyrintzis
Publisher:
ISBN:
Category : Aerodynamics, Transonic
Languages : en
Pages : 306
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Book Description
Author: Shyue-bin Chang
Publisher:
ISBN:
Category : Aerodynamic noise
Languages : en
Pages : 354
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Book Description
Author: Henry E. Jones
Publisher:
ISBN:
Category : Unsteady flow (Aerodynamics)
Languages : en
Pages : 96
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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.
Author: G. R. Srinivasan
Publisher:
ISBN:
Category :
Languages : en
Pages : 20
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Book Description
A computational procedure and some numerical results of unsteady interaction of a helicopter rotor blade with a Lamb-like vortex of finite viscous core in subsonic and transonic flows is presented. The interaction considered here is one of the limiting cases of a more complex interaction typically encountered on helicopter rotor blade. In this limit, the interacting flow field is considered to be unsteady but two-dimensional. Accordingly, unsteady, two-dimensional, thin-layer Navier-Stokes equations are solved using a prescribed-vortex method (also called perturbation method) for the cases of stationary and moving rotor blades encountering a moving vortex passing the blades. The numerical results are compared with the recent experimental data of Caradonna et al. for the latter case. The comparison shows that for the transonic cases, the flow field is dominated by the presence of the shock waves, with strong indications of unsteady time lags in the shock-wave motions and shock-wave strengths, and of important three-dimensional effects. For subcritical-flow cases, however, the unsteady lag effects on the basic rotor blade are absent, and three-dimensional effects appear to be negligible, unlike the supercritical case. The subcritical calculations are in good agreement with the experimental data.
Author: San-Yih Lin
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 226
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 20
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Book Description
Unsteady interactions of strong concentrated vortices, distributed gusts, and sharp-edged gusts with stationary airfoils have been analyzed in two-dimensional transonic flow. A simple and efficient method for introducing such vortical disturbances has been implemented in numerical codes that range from inviscid transonic small disturbance to thin-layer Navier Stokes. The numerical results demonstrate the large distortions in the overall flow field and in the surface air loads that are produced by various vortical interactions. The results of the different codes are in excellent qualitative agreement, but, as might expected, the transonic small-disturbance calculations are deficient in the important region near the leading edge. Keywords include: Gusts, Vortex interaction, Unsteady transonic flow, and Computational aerodynamics.
Author: Rajneesh K. Singh
Publisher:
ISBN:
Category : Aerodynamics, Transonic
Languages : en
Pages : 532
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Book Description
Author: M. S. Howe
Publisher: Cambridge University Press
ISBN: 9780521012232
Category : Mathematics
Languages : en
Pages : 236
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