Acoustic Wave Propagation II: Heat Release, Complex Geometry, and Mean Flow Effects

Inside micro cavities, specific dissipative mechanisms influencing acoustic wave propagation occur due to viscous and heat-conducting nature of the fluid. This work focuses on a possible extension of the so called “Low Reduced Frequency” model for acoustic wave propagation in a thermoviscous fluid. This extension is built starting from geometrical and physical assumptions (boundary layer theory, straight waveguides) and consists in the incorporation of a stationary laminar and subsonic mean flow. The resulting equivalent fluid model provides a new damping coefficient which depends on the Mach number, the shear and thermal wave numbers and the cross-sectional profiles of axial velocity and temperature. The main application area is the study of acoustic attenuation within automotive catalytic converters or also thin fluid layers like cooling systems in small electronic devices. This formulation has been implemented for a simple one dimensional thin tube. Convergence to the original model in the absence of mean flow has been reached and comparisons with variational solutions given by Peat show good agreements.

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Acoustic Wave Propagation i n a Variable Area Duct Carrying a Mean Flow

10.2514/6.1984-2336 ◽

1984 ◽

Author(s):

C. THOMPSON ◽

R. SEN

Keyword(s):

Wave Propagation ◽

Acoustic Wave ◽

Mean Flow ◽

Acoustic Wave Propagation

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Surge Model: Predicting Damping and Excitation Frequencies of Complex Pumping Systems

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications ◽

10.1115/89-gt-93 ◽

1989 ◽

Author(s):

Alexander Lifson ◽

Cecil R. Sparks

Keyword(s):

Experimental Data ◽

Wave Propagation ◽

Acoustic Wave ◽

Frequency Domain Analysis ◽

Mode Shapes ◽

Mean Flow ◽

Acoustic Wave Propagation ◽

Pressure Losses ◽

Operating Points ◽

Interactive Dynamic

Frequency domain analysis is presented to define susceptibility of complex pumping systems to surge oscillations. In the analysis, piping spans are considered as distributed elements, compressors or pumps, orifices, valves, and junctions as lumped acoustic four pole elements. The piping elements are connected into one network through the use of appropriate matching boundary conditions. The analysis is most readily applicable to single stage units, typical of gas transmission stations. The surge model is based on predicting damping (logarithmic decrement values) and mode shapes for pressure and flow pulsations of the interactive dynamic system at its various natural acoustic frequencies. The system design is optimized by assuring that all operating points are sufficiently removed from surge, i.e., logarithmic decrements are above certain specified value. The effects of mean flow on acoustic wave propagation, pipe friction, viscothermal dissipation, and pressure losses at various piping locations (junctions, valves, orifices) are accounted for in the model. Results of the computational modeling of a complex centrifugal compressor system is presented. The analytical model is also verified by comparing the analytical results with experimental data.

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