Coupled Fan–Stator Aerodynamic and Acoustic Response to Inflow Distortion

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
H. M. Atassi ◽  
A. V. Kozlov ◽  
A. A. Ali ◽  
D. A. Topol
Keyword(s):  
Power Level ◽  
Scattering Matrix ◽  
Acoustic Mode ◽  
Coupling Mechanism ◽  
Acoustic Response ◽  
Sound Power Level ◽  
3D Geometry ◽  
Transonic Fan ◽  
Acoustic Spectra ◽  
The Relationship

Abstract Turbofan rotor–stator aeromechanic and aeroacoustics modeling has been traditionally developed by considering separately the aerodynamic and acoustic response of the fan and the stator to inflow nonuniformities. The present paper develops a model for the coupled fan–stator response for a realistic 3D geometry. The coupling mechanism is assumed to be mainly carried by scattered waves bouncing back and forth between the fan and the stator. The relationship between sources and state elements at three regions (inlet (1), in-between fan and stator (2), and exit (3)) is derived in terms of a scattering matrix S. The model is applied to two fan configurations: (1) a fully subsonic fan and (2) a transonic tip speed fan. The scattering matrix terms, up to the 5th blade passing frequency (BPF), are calculated by using CAAT, an Euler-based code. Results show coupling adds about 6 dB to the sound power level (PWL) of the transonic fan configuration but has a small effect for the subsonic fan configuration. The analysis of the propagating modes shows that, for the transonic configuration, the inlet mode at 1BPF propagates in regions 2 and 3 but is cut off in region 1. This reinforces the coupling process by trapping the acoustic mode 1BPF in region 2. Although this trapped energy is mainly due to the 1BPF of the fan wake, the fan scatters this energy into higher order acoustic modes and thus produces redistribution toward higher frequency of the acoustic spectra. Finally, adding a liner in region 2 reduces the energy of 1BPF mode propagating upstream and impinging on the fan. This mitigates the effect of the fan–stator coupling.

VIBRO-ACOUSTIC RESPONSE OF A CIRCULAR ISOTROPIC CYLINDRICAL SHELL UNDER A THERMAL ENVIRONMENT

2011 ◽  
Vol 03 (03) ◽  
pp. 525-541 ◽  
Author(s):  
P. JEYARAJ ◽  
C. PADMANABHAN ◽  
N. GANESAN
Keyword(s):  
Cylindrical Shell ◽  
Thermal Environment ◽  
Power Level ◽  
Mode Shapes ◽  
Sound Power ◽  
Sudden Increase ◽  
Acoustic Response ◽  
Response Characteristics ◽  
Sound Power Level ◽  
Isotropic Cylindrical Shell

This paper presents numerical simulation studies on the vibration and acoustic response-characteristics of an isotropic cylindrical shell under a thermal environment using commercial softwares ANSYS and SYSNOISE. First, the critical buckling temperature is obtained, followed by modal and harmonic response analyses considering pre-stress due to the thermal field in the cylindrical shell, with the critical buckling temperature as a parameter. The vibration response predicted is then used to compute the sound radiation. It is found that there is a significant change in the vibration mode shapes and ring frequency towards the lowest natural frequency with an increase in temperature. There is a sudden increase in overall sound power level near the critical buckling temperature and significant changes in mode shapes with temperature does not affect the overall sound power level.

scholarly journals Theoretical and Numerical Estimation of Vibroacoustic Behavior of Clamped Free Parabolic Tapered Annular Circular Plate with Different Arrangement of Stiffener Patches

2018 ◽  
Vol 8 (12) ◽  
pp. 2542 ◽  
Author(s):  
Abhijeet Chatterjee ◽  
Vinayak Ranjan ◽  
Mohammad Azam ◽  
Mohan Rao
Keyword(s):  
Circular Plate ◽  
Acoustic Radiation ◽  
Power Level ◽  
Radiation Efficiency ◽  
Thickness Variation ◽  
Sound Power ◽  
The Finite Element Method ◽  
Acoustic Response ◽  
Sound Power Level ◽  
Design Options

This paper compares the vibroacoustic behavior of a tapered annular circular plate having different parabolic varying thickness with different combinations of rectangular and concentric stiffener patches keeping the mass of the plate and the patch constant for a clamped-free boundary condition. Both numerical and analytical methods are used to solve the plate. The finite element method (FEM) is used to determine the vibration characteristic and both Rayleigh integral and FEM is used to determine the acoustic behavior of the plate. It is observed that a Case II plate with parabolic decreasing–increasing thickness variation for a plate with different stiffener patches shows reduction in frequency parameter in comparison to other cases. For acoustic response, the variation of peak sound power level for different combinations of stiffener patches is investigated with different taper ratios. It is investigated that Case II plate with parabolic decreasing–increasing thickness variation for an unloaded tapered plate as well as case II plate with 2 rectangular and 4 concentric stiffeners patches shows the maximum sound power level among all variations. However, it is shown that the Case III plate with parabolically increasing–decreasing thickness variation with different combinations of rectangular and concentric stiffeners patches is least prone to acoustic radiation. Furthermore, it is shown that at low forcing frequency, average radiation efficiency with different combinations of stiffeners patches remains the same, but at higher forcing frequency a higher taper ratio causes higher radiation efficiency, and the radiation peak shifts towards the lower frequency and alters its stiffness as the taper ratio increases. Finally, the design options for peak sound power actuation and reduction for different combinations of stiffener patches with different taper ratios are suggested.

Acoustic Modes in the Annular Duct with Uniform Mean Flow

2011 ◽  
Vol 214 ◽  
pp. 554-558 ◽  
Author(s):  
Zhan Xin Liu
Keyword(s):  
Power Level ◽  
Angular Frequency ◽  
Acoustic Mode ◽  
Mode Number ◽  
Benchmark Problems ◽  
Energy Relation ◽  
Mean Flow ◽  
Azimuthal Mode ◽  
Sound Power Level ◽  
Annular Duct

There are many benchmark problems in computational aeroacoustics (CAA) and acoustic mode in the annular duct with uniform mean flow is a problem of this kind. The energy relation of the duct mode is deduced from the governing equation, Euler equations in this paper. If the sound power level, angular frequency, azimuthal mode number and radial mode number are given, the acoustic mode in the annular duct can be expressed explicitly by the deduced results. The simulation of two different cases shows the propagation of a single acoustic mode in annular duct pictorially.

The Application of Computational Fluid Dynamics to the Prediction of Flow Generated Noise: Part 2: Turbulence-Based Prediction Technique

1998 ◽  
Vol 5 (3) ◽  
pp. 201-215 ◽  
Author(s):  
C M Mak ◽  
D J Oldham
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Power Level ◽  
Turbulence Models ◽  
Simulation Models ◽  
Acoustic Power ◽  
Cfd Simulations ◽  
Sound Power Level ◽  
Prediction Technique ◽  
The Relationship

In this paper an engineering approach is followed to investigate the feasibility of developing a method in which information provided by standard CFD turbulence models can be employed as the basis of an airflow noise prediction technique. To this end, experimental results obtained by previous investigators have been processed and compared with CFD predictions. The turbulence-based predictive technique investigated was based on the relationship between the acoustic power radiated due to the interaction of airflow and a spoiler and the turbulent kinetic energy generated in the region of the spoiler. The sound power level of regenerated noise determined experimentally was related to the turbulent kinetic energy in the vicinity of spoiler provided by CFD simulations of the relevant configurations. A collapse of the data from the simulation models was obtained against the experimental data. The data collapse for a particular spoiler was generally excellent for the higher Strouhal numbers but was less good at lower Strouhal numbers where considerable scatter was observed.

REMOVED: Investigating the sound power level of a simplified underwater vehicle induced by flow separation

2020 ◽  
Vol 204 ◽  
pp. 107286
Author(s):  
Deng Rui ◽  
Zhang Zezhen ◽  
Pang Fuzhen ◽  
Wu Tiecheng ◽  
Luo Wanzhen
Keyword(s):  
Flow Separation ◽  
Power Level ◽  
Underwater Vehicle ◽  
Sound Power ◽  
Sound Power Level
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