Helicopter Model Rotor-blade Vortex Interaction Impulsive Noise: Scalability and Parametric Variations PDF Download
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Languages : en
Pages : 36
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Book Description
Acoustic data taken in the anechoic Deutsch-NIederlaendischer Windkanal (DNW) have documented the blade-vortex interaction (BVI) impulsive noise radiated from 1/7-scale model main rotor of the AH-1 series helicopter. Average model-scale data were compared with averaged full-scale, in-flight acoustic data under similar nondimensional test conditions. At low advance ratios (mu = 0.164-0.194), the data scale remarkably well in level and waveform shape, and also duplicate the directivity pattern of BVI impulsive noise. At moderate advance ratios (mu = 0.224-0.270), the scaling deteriorates, suggesting that the model-scale rotor is not adequately simulating the full-scale BVI noise; presently, no proved explanation of this discrepancy exists. Carefully performed parametric variations over a complete matrix of testing conditions have shown that all of the four governing nondimensional parameters -- tip Mach number at hover, advance ratio, local inflow ratio, and thrust coefficient -- are highly sensitive to BVI noise radiation. Keywords: Helicopter noise; Blade vortex interaction; Measured acoustics.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 36
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Book Description
Acoustic data taken in the anechoic Deutsch-NIederlaendischer Windkanal (DNW) have documented the blade-vortex interaction (BVI) impulsive noise radiated from 1/7-scale model main rotor of the AH-1 series helicopter. Average model-scale data were compared with averaged full-scale, in-flight acoustic data under similar nondimensional test conditions. At low advance ratios (mu = 0.164-0.194), the data scale remarkably well in level and waveform shape, and also duplicate the directivity pattern of BVI impulsive noise. At moderate advance ratios (mu = 0.224-0.270), the scaling deteriorates, suggesting that the model-scale rotor is not adequately simulating the full-scale BVI noise; presently, no proved explanation of this discrepancy exists. Carefully performed parametric variations over a complete matrix of testing conditions have shown that all of the four governing nondimensional parameters -- tip Mach number at hover, advance ratio, local inflow ratio, and thrust coefficient -- are highly sensitive to BVI noise radiation. Keywords: Helicopter noise; Blade vortex interaction; Measured acoustics.
Author: F. H. Schmitz
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ISBN:
Category :
Languages : en
Pages : 110
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Book Description
The theoretical and experimental status of helicopter impulsive noise is reviewed. The two major source mechanisms of helicopter impulsive noise are addressed: high-speed impulsive noise and blade-vortex interaction impulsive noise. A thorough physical explanation of both generating mechanisms is presented together with model and full-scale measurements of the phenomena. Current theoretical prediction methods are compared with experimental findings of isolated rotor tests. The noise generating mechanisms of high speed impulsive noise are fairly well understood - theory and experiment compare nicely over Mach number ranges typical of today's helicopters. For the case of blade-vortex interaction noise, understanding of noise generating mechanisms and theoretical comparison with experiment are less satisfactory. Several methods for improving theory-experiment are suggested.
Author: Juan Abelló
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ISBN:
Category :
Languages : en
Pages : 466
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Author: Andrew B. Connor
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Category : Helicopters
Languages : en
Pages : 28
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Author: Ruth McVoy Martin
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Category : Acoustical engineering
Languages : en
Pages : 48
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Author:
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ISBN:
Category : Acoustical engineering
Languages : en
Pages : 48
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Author: Danny R. Hoad
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Category : Rotors (Helicopters)
Languages : en
Pages : 112
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Author:
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ISBN:
Category :
Languages : en
Pages : 280
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Book Description
Author: Danny R. Hoad
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ISBN:
Category : Acoustical engineering
Languages : en
Pages : 84
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 84
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Book Description
