Duct Acoustics

2021 ◽  
Author(s):  
Erkan Dokumacı
Keyword(s):  
Duct Acoustics

scholarly journals Structural Response of a Single-Stage Centrifugal Compressor to Fluid-Induced Excitations at Low-Flow Operating Condition: Experimental and Numerical Study

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4292
Author(s):  
Kirill Kabalyk ◽  
Andrzej Jaeschke ◽  
Grzegorz Liśkiewicz ◽  
Michał Kulak ◽  
Tomasz Szydłowski ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Numerical Study ◽  
Structural Response ◽  
Flow Coefficient ◽  
Low Flow ◽  
Dynamic Strain ◽  
Duct Acoustics ◽  
Numerical Noise ◽  
Partial Load ◽  
Compressor Impeller

The article describes an assessment of possible changes in constant fatigue life of a medium flow-coefficient centrifugal compressor impeller subject to operation at close-to-surge point. Some aspects of duct acoustics are additionally analyzed. The experimental measurements at partial load are presented and are primarily used for validation of unidirectionally coupled fluid-structural numerical model. The model is based on unsteady finite-volume fluid-flow simulations and on finite-element transient structural analysis. The validation is followed by the model implementation to replicate the industry-scale loads with reasonably higher rotational speed and suction pressure. The approach demonstrates satisfactory accuracy in prediction of stage performance and unsteady flow field in vaneless diffuser. The latter is deduced from signal analysis relying on continuous wavelet transformations. On the other hand, it is found that the aerodynamic incidence losses at close-to-surge point are underpredicted. The structural simulation generates considerable amounts of numerical noise, which has to be separated prior to evaluation of fluid-induced dynamic strain. The main source of disturbance is defined as a stationary region of static pressure drop caused by flow contraction at volute tongue and leading to first engine-order excitation in rotating frame of reference. Eventually, it is concluded that the amplitude of excitation is too low to lead to any additional fatigue.

Response Surface Method Optimization of Uniform and Axially Segmented Duct Acoustics Liners

2006 ◽  
Vol 43 (4) ◽  
pp. 1089-1102 ◽  
Author(s):  
L. Lafronza ◽  
A. McAlpine ◽  
A. J. Keane ◽  
R. J. Astley
Keyword(s):  
Response Surface ◽  
Response Surface Method ◽  
Duct Acoustics ◽  
Surface Method ◽  
Method Optimization

Study of the Acoustic Oscillations by Flows Over Cavities: Part 1 — Internal Flows

2002 ◽  
Author(s):  
Xavier Amandole`se ◽  
Pascal He´mon ◽  
Clotilde Regardin
Keyword(s):  
Lattice Gas ◽  
Acoustic Mode ◽  
Sound Level ◽  
Acoustic Oscillations ◽  
Helmholtz Instability ◽  
Internal Flows ◽  
Duct Acoustics ◽  
Neck Thickness ◽  
High Sound ◽  
Very High

We present a study of acoustic oscillations induced by an internal airflow over a shallow and a deep cavity. The Kelvin-Helmholtz instability is interacting with an acoustic mode of the duct, leading to a resonance which produces a very high sound level. The influence of upstream boundary layer thickness and neck thickness is studied. Some results obtained by modifying the upstream lip shape, by crenel addition, are also given. It is also shown that the numerical simulations using a lattice-gas method give relatively good results by comparison with the experiments. Especially the resonance with the duct acoustics was qualitatively reproduced.

Perfect, broadband, and sub-wavelength absorption with asymmetric absorbers: Realization for duct acoustics with 3D printed porous resonators

2021 ◽  
pp. 116687
Author(s):  
Jean Boulvert ◽  
Thomas Humbert ◽  
Vicente Romero-García ◽  
Gwénaël Gabard ◽  
Edith Roland Fotsing ◽  
...  
Keyword(s):  
Duct Acoustics ◽  
Wavelength Absorption ◽  
3D Printed ◽  
Sub Wavelength

Duct Acoustics

2008 ◽  
pp. 595-791
Author(s):  
Fridolin P. Mechel
Keyword(s):  
Duct Acoustics

scholarly journals EVALUATION OF SEVERAL NONREFLECTING COMPUTATIONAL BOUNDARY CONDITIONS FOR DUCT ACOUSTICS

1995 ◽  
Vol 03 (04) ◽  
pp. 327-342 ◽  
Author(s):  
WILLIE R. WATSON ◽  
WILLIAM E. ZORUMSKI ◽  
STEVE L. HODGE
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Sound Propagation ◽  
Sparse Matrix ◽  
Nonlocal Boundary Condition ◽  
Nonlocal Boundary ◽  
Substantial Reduction ◽  
Sound Attenuation ◽  
Interior Solution ◽  
Duct Acoustics

Several nonreflecting computational boundary conditions that meet certain criteria and have potential applications to duct acoustics are evaluated for their effectiveness. The same interior solution scheme, grid, and order of approximation are used to evaluate each condition. Sparse matrix solution techniques are applied to solve the matrix equation resulting from the discretization. Modal series solutions for the sound attenuation in an infinite duct are used to evaluate the accuracy of each nonreflecting boundary condition. The evaluations are performed for sound propagation in a softwall duct, for several sources, sound frequencies, and duct lengths. It is shown that a recently developed nonlocal boundary condition leads to sound attenuation predictions considerably more accurate than the local ones considered. Results also show that this condition is more accurate for short ducts. This leads to a substantial reduction in the number of grid points when compared to other nonreflecting conditions.

A Theoretically Based Valve Noise Prediction Method for Compressible Fluids

1986 ◽  
Vol 108 (3) ◽  
pp. 329-338 ◽  
Author(s):  
G. Reethof ◽  
W. C. Ward
Keyword(s):  
Transmission Loss ◽  
Prediction Method ◽  
Low Noise ◽  
Compressible Fluids ◽  
Noise Prediction ◽  
Duct Acoustics ◽  
Proper Design ◽  
Predicted Values ◽  
Mode Generation ◽  
Wide Pressure

Noise generated by control valves in power generation, chemical and petrochemical plants must be predictable so that proper design measures can be taken to conform to OSHA’s noise regulation. Currently available noise prediction methods are empirically based and not sufficiently accurate. The method proposed is based on jet noise theory for both subcritical and choked conditions, duct acoustics theory in terms of higher order mode generation and propagation, and the theory of acoustics-structure interaction in the development of the transmission loss values for the pipe. One third octave values are calculated over the audio spectrum by incorporating spectral aspects of noise generation, propagation, transmission, and radiation. The predicted values of noise for several size cage globe valves over wide pressure ranges compare well with measured results by two prominent valve manufacturers. The method, at present, is restricted to conventional valve styles, as opposed to the special low noise valve types with their very complicated orificial elements.

Coupling Between Acoustic Resonance and Fluidelastic Instability in Normal Triangular Tube Arrays

2006 ◽  
Author(s):  
John Mahon ◽  
Craig Meskell
Keyword(s):  
Flow Velocity ◽  
Sound Pressure ◽  
Physical Mechanism ◽  
Acoustic Resonance ◽  
Acoustic Power ◽  
Structural Damping ◽  
Duct Acoustics ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Independent Parameters

This paper reports on the interaction between fluidelastic instability (FEI) and acoustic resonance. In order to examine the interaction, the duct acoustics were excited with speakers placed adjacent to the tube array to artificially replicate flow-induced acoustic resonance. While the current study has clearly captured the phenomenon of interaction between the fluidelastic motion at ∼ 10 Hz and the acoustic field at ∼ 1kHz, it is not apparent what the physical mechanism at work might be. The paper details the effect on RMS level of tube vibration for three independent parameters: flow velocity, structural damping and acoustic power. The results presented show that there is a corresponding fall in the FEI vibration amplitude with increasing sound pressure level in the tube array. In addition, the effects of flow velocity and structural damping in conjunction with forced acoustics on the RMS of tube displacement are discussed.

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