Two-dimensional model of low Mach number vortex sound generation in a lined duct

2009 ◽  
Vol 126 (3) ◽  
pp. 1005-1014 ◽  
Author(s):  
S. K. Tang ◽  
C. K. Lau
Keyword(s):  
Mach Number ◽  
Two Dimensional ◽  
Sound Generation ◽  
Dimensional Model ◽  
Low Mach Number ◽  
Vortex Sound ◽  
Two Dimensional Model

Sound Generation in Subsonic Turbomachinery

1970 ◽  
Vol 92 (3) ◽  
pp. 450-458 ◽  
Author(s):  
C. L. Morfey
Keyword(s):  
Broad Band ◽  
Axial Flow ◽  
Two Dimensional ◽  
Sound Generation ◽  
Dimensional Model ◽  
Frequency Sound ◽  
Discrete Frequency ◽  
Two Dimensional Model

Sources of noise in axial-flow machines are studied theoretically with the aid of a simplified two-dimensional model. The analysis leads to estimates of the discrete-frequency sound output from interacting blade rows, and provides a basis for subsequent study of broad-band sources.

Why Do Vortices Generate Sound?

1995 ◽  
Vol 117 (B) ◽  
pp. 252-260 ◽  
Author(s):  
Alan Powell
Keyword(s):  
Mach Number ◽  
Incompressible Flow ◽  
Vortex Rings ◽  
Inviscid Fluid ◽  
Fluid Density ◽  
Sound Generation ◽  
Simple Argument ◽  
Low Mach Number ◽  
Vortex Sound ◽  
Moving Vortex

Emphasizing physical pictures with a minimum of analysis, an introductory account is presented as to how vortices generate sound. Based on the observation that a vortex ring induces the same hydrodynamic (incompressible) flow as does a dipole sheet of the same shape, simple physical arguments for sound generation by vorticity are presented, first in terms of moving vortex rings of fixed strength and then of fixed rings of variable strength. These lead to the formal results of the theory of vortex sound, with the source expressed in terms of the vortex force ρ(u∧ ζ) and of the form introduced by Mo¨hring in terms of the vortex moment (y∧ ζ′), (ρ is the constant fluid density, u the flow velocity, ζ = ∇ ∧u the vorticity and y is the flow coordinate). The simple “Contiguous Method” of finding the contiguous acoustic field surrounding an acoustically compact hydrodynamic (incompressible) field is also discussed. Some very simple vortex flows illustrate the various ideas. These are all for acoustically compact, low Mach number flows of an inviscid fluid, except that a simple argument for the effect of viscous dissipation is given and its relevance to the “dilatation” of a vortex is mentioned.

Why Do Vortices Generate Sound?

1995 ◽  
Vol 117 (B) ◽  
pp. 252-260 ◽  
Author(s):  
Alan Powell
Keyword(s):  
Mach Number ◽  
Incompressible Flow ◽  
Vortex Rings ◽  
Inviscid Fluid ◽  
Fluid Density ◽  
Sound Generation ◽  
Simple Argument ◽  
Low Mach Number ◽  
Vortex Sound ◽  
Moving Vortex

Emphasizing physical pictures with a minimum of analysis, an introductory account is presented as to how vortices generate sound. Based on the observation that a vortex ring induces the same hydrodynamic (incompressible) flow as does a dipole sheet of the same shape, simple physical arguments for sound generation by vorticity are presented, first in terms of moving vortex rings of fixed strength and then of fixed rings of variable strength. These lead to the formal results of the theory of vortex sound, with the source expressed in terms of the vortex force ρ(u∧ ζ) and of the form introduced by Mo¨hring in terms of the vortex moment (y∧ ζ′), (ρ is the constant fluid density, u the flow velocity, ζ = ∇ ∧u the vorticity and y is the flow coordinate). The simple “Contiguous Method” of finding the contiguous acoustic field surrounding an acoustically compact hydrodynamic (incompressible) field is also discussed. Some very simple vortex flows illustrate the various ideas. These are all for acoustically compact, low Mach number flows of an inviscid fluid, except that a simple argument for the effect of viscous dissipation is given and its relevance to the “dilatation” of a vortex is mentioned.

Commitment to pro- versus counter-attitudinal behavior and the dynamics of social representations

2002 ◽  
Vol 61 (1) ◽  
pp. 34-44 ◽  
Author(s):  
Eric Tafani ◽  
Lionel Souchet
Keyword(s):  
Higher Education ◽  
Social Representations ◽  
Cognitive Restructuring ◽  
Social Representation ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Social Actions ◽  
The Social ◽  
Two Dimensional Model ◽  
Students Attitudes

This research uses the counter-attitudinal essay paradigm ( Janis & King, 1954 ) to test the effects of social actions on social representations. Thus, students wrote either a pro- or a counter-attitudinal essay on Higher Education. Three forms of counter-attitudinal essays were manipulated countering respectively a) students’ attitudes towards higher education; b) peripheral beliefs or c) central beliefs associated with this representation object. After writing the essay, students expressed their attitudes towards higher education and evaluated different beliefs associated with it. The structural status of these beliefs was also assessed by a “calling into question” test ( Flament, 1994a ). Results show that behavior challenging either an attitude or peripheral beliefs induces a rationalization process, giving rise to minor modifications of the representational field. These modifications are only on the social evaluative dimension of the social representation. On the other hand, when the behavior challenges central beliefs, the same rationalization process induces a cognitive restructuring of the representational field, i.e., a structural change in the representation. These results and their implications for the experimental study of representational dynamics are discussed with regard to the two-dimensional model of social representations ( Moliner, 1994 ) and rationalization theory ( Beauvois & Joule, 1996 ).

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