Excitation of an Axisymmetric Shear Alfvén Wave by a Rogowski-Type Antenna

The present investigation is an analysis of self-excited combustion instability in a swirl flame-based combustor with transverse extensions. Transverse extensions create the possibility of studying flame interaction with transverse acoustic oscillations. Such investigation important for understanding the phenomenon of thermoacoustic instability in annular combustors, where during thermoacoustic instability, azimuthal acoustic modes of the combustor couple with the multiple flames of the combustor. Flame and flow field dynamics during self-excited thermoacoustic instability in the single burner test-rig is presented here. These results are then compared to the dynamics of the isothermal and reacting flows in response to axial and transverse acoustic forcing. Both axial and transverse forcing led to the formation of axisymmetric shear layer vortices. Adding to the insight gained from previous investigations, these results suggest that that swirl flow dynamics in response to transverse acoustics consists of a non-trivial, direct effect of transverse acoustics on the flow field, in addition to its response to longitudinal fluctuations induced by transverse forcing.

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Noise from an axisymmetric shear flow: I numerical results

Mechanics Research Communications ◽

10.1016/0093-6413(79)90013-2 ◽

1979 ◽

Vol 6 (2) ◽

pp. 61-68

Author(s):

A.L. Chandraker ◽

M.L. Munjal

Keyword(s):

Shear Flow ◽

Numerical Results ◽

Axisymmetric Shear

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The stability of countercurrent mixing layers in circular jets

Journal of Fluid Mechanics ◽

10.1017/s0022112091000137 ◽

1991 ◽

Vol 227 ◽

pp. 309-343 ◽

Cited By ~ 77

Author(s):

P. J. Strykowski ◽

D. L. Niccum

Keyword(s):

Shear Layer ◽

Critical Velocity ◽

Velocity Ratio ◽

Mixing Layer ◽

Mixing Layers ◽

Mean Velocity ◽

Axisymmetric Vortex ◽

Circular Jets ◽

Axisymmetric Shear ◽

The Stability

A spatially developing countercurrent mixing layer was established experimentally by applying suction to the periphery of an axisymmetric jet. A laminar mixing region was studied in detail for a velocity ratio R = ΔU/2U between 1 and 1.5, where ΔU describes the intensity of the shear across the layer and U is the average speed of the two streams. Above a critical velocity ratio Rr = 1.32 the shear layer displays energetic oscillations at a discrete frequency which are the result of very organized axisymmetric vortex structures in the mixing layer. The spatial order of the primary vortices inhibits the pairing process and dramatically alters the spatial development of the shear layer downstream. Consequently, the turbulence level in the jet core is significantly reduced, as is the decay rate of the mean velocity on the jet centreline. The response of the shear layer to controlled external forcing indicates that the shear layer oscillations at supercritical velocity ratios are self-excited. The experimentally determined critical velocity ratio of 1.32, established for very thin axisymmetric shear layers, compares favourably with the theoretically predicted value of 1.315 for the transition from convective to absolute instability in plane mixing layers (Huerre & Monkewitz 1985).

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The low frequency sound from multipole sources in axisymmetric shear flows. Part 2

Journal of Fluid Mechanics ◽

10.1017/s0022112076000104 ◽

1976 ◽

Vol 75 (1) ◽

pp. 17-28 ◽

Cited By ~ 17

Author(s):

M. E. Goldstein

Keyword(s):

Shear Flows ◽

Acoustic Radiation ◽

Previous Analysis ◽

Low Frequency ◽

Frequency Sound ◽

Doppler Factor ◽

Axisymmetric Shear ◽

Multipole Sources

A previous analysis of the acoustic radiation from multipole sources is extended to include additional components of the dipole and quadrupole sources. It is found that, unlike the components of the sources considered in the previous paper, the exponent of the Doppler factor now depends on the location of the sources within the jet.

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