Numerical study of sound field radiated from a circular duct with an open end

1998 ◽  
Vol 103 (5) ◽  
pp. 2839-2839
Author(s):  
Zhichi Zhu ◽  
Anqi Zhou ◽  
Dongtao Huang ◽  
Qing Guo
Keyword(s):  
Numerical Study ◽  
Sound Field ◽  
Circular Duct

Active control of fan noise from high-bypass ratio aeroengines: a numerical study

2001 ◽  
Vol 105 (1053) ◽  
pp. 627-631
Author(s):  
P. Traub ◽  
F. Kennepohl ◽  
K. Heinig
Keyword(s):  
Active Control ◽  
Numerical Study ◽  
Active Noise Control ◽  
Sound Field ◽  
Primary Objective ◽  
Scale Model ◽  
Research Centre ◽  
Infinite Length ◽  
Circular Duct ◽  
Bypass Ratio

Abstract Under the national research project, dubbed Turbotech II, in which MTU Aero Engines, DLR Institute of Propulsion Technology and EADS Corporate Research Centre participate, active noise control (ANC) has been tested with a scale model fan of one metre diameter for a high bypass ratio aeroengine. MTU’s task in this project was to develop a computer code to predict the sound field in the intake duct of the fan-rig by the use of active control. The primary objective of the numerical study was to specify numbers of actuators (loudspeakers) and error sensors (microphones) and their positioning to control the harmonic sound power, radiated upstream to the duct intake. The computer model is based on the geometry of an annular or circular duct of rigid walls and infinite length, containing a subsonic axial uniform flow. The modal amplitudes of the primary sound field are input data. The actuators are modelled by acoustic monopoles. Two control algorithms have been used for achieving the control objective. The first consists simply in the reduction of the in-duct mean squared pressures. The second, so called modal control, is designed to cancel dominant modes selectively. Numerical results are presented using a typical configuration of wall mounted actuators and error sensors in the form of a number of rings uniformly distributed along the length of the intake duct. Guidelines have also been derived to design a favourable configuration of actuators and sensors. The findings of the numerical study are compared with the results of the ANC tests.

Numerical Study on Air-Reed Instruments With LES

2011 ◽  
Author(s):  
Kin’ya Takahashi ◽  
Masataka Miyamoto ◽  
Yasunori Ito ◽  
Toshiya Takami ◽  
Taizo Kobayashi ◽  
...  
Keyword(s):  
Numerical Study ◽  
Sound Field ◽  
Acoustic Analogy ◽  
Empirical Theory ◽  
Sound Sources ◽  
Aerodynamic Sound ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Semi Empirical ◽  
2D And 3D

The acoustic mechanisms of 2D and 3D edge tones and a 2D small air-reed instrument have been studied numerically with compressible Large Eddy Simulation (LES). Sound frequencies of the 2D and 3D edge tones obtained numerically change with the jet velocity well following Brown’s semi-empirical equation, while that of the 2D air-reed instrument behaves in a different manner and obeys the semi-empirical theory, so called Cremer-Ising-Coltman theory. We have also calculated aerodynamic sound sources for the 2D edge tone and the 2D air-reed instrument relying on Ligthhill’s acoustic analogy and have discussed similarities and differences between them. The sound source of the air-reed instrument is more localized around the open mouth compared with that of the edge tone due to the effect of the strong sound field excited in the resonator.

Destabilization of Laminar Wall Jet Flow and Relaminarization of the Turbulent Confined Jet Flow in Axially Rotating Circular Pipe

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Snehamoy Majumder ◽  
Dipankar Sanyal
Keyword(s):  
Swirling Flow ◽  
Numerical Study ◽  
Azimuthal Velocity ◽  
Jet Flow ◽  
Wall Jet ◽  
Local Velocity ◽  
Recirculation Bubble ◽  
Circular Duct ◽  
Streamline Curvature ◽  
Wall Jet Flow

Destabilization and relaminarization phenomena have been investigated in an axially rotating circular duct. Standard k-ε model with modification for streamline curvature has been used in the numerical study. The laminar and turbulent velocity distributions at inlet have been observed to become turbulent and laminar, respectively, toward the exit of the pipe. A local velocity profile with parabolic or nearly uniform variation has been considered as the characteristic of laminarlike or turbulent flow, respectively, and changeover of flow from former to the later variation or vice versa has been taken to characterize destabilization and relaminarization, respectively. The predicted azimuthal velocity component was found to be reasonably accurate near the wall and not so encouraging in the core region of the swirling flow. The recirculation bubble generated by a central jet flow at the wall has been observed to reduce in size due to rotation of the pipe confirming the relaminarization phenomenon, whereas with laminar wall jet waspredicted recirculation bubble growing with rotation rate manifesting the destabilization effects.

Numerical Study of Active Control of Interior Noise in a Structural-Acoustic Enclosure

2011 ◽  
Vol 486 ◽  
pp. 103-106
Author(s):  
Ming Gang Zhu ◽  
Guo Yong Jin ◽  
Na Feng
Keyword(s):  
Control System ◽  
Active Control ◽  
Lead Zirconate Titanate ◽  
Numerical Study ◽  
Sound Field ◽  
Lead Zirconate ◽  
Interior Noise ◽  
Placement Problem ◽  
Total Potential ◽  
Flexible Plates

This paper is concerned with the numerical study of active control of interior noise induced by the flexible plates in a coupled enclosure. A cabin-like enclosure with four acoustically rigid walls and two flexible plates is considered. Two types of actuators are used, i.e. acoustic actuators and distributed lead zirconate titanate piezoelectric (PZT) actuators instead of point force actuators. With the control system designed to globally reduce the sound field, different control configurations are considered, including the structural actuator on the incident panel, actuator on the receiving panel, acoustic actuator on the cavity, and their combinations. The effectiveness and performance of the control system corresponding to each configuration are studied numerically, and desirable placement problem of structural actuators in terms of total potential energy reduction are of particular interest.

A TECHNIQUE FOR PLANE-SYMMETRIC SOUND FIELD ANALYSIS IN THE FAST MULTIPOLE BOUNDARY ELEMENT METHOD

2005 ◽  
Vol 13 (01) ◽  
pp. 71-85 ◽  
Author(s):  
Y. YASUDA ◽  
T. SAKUMA
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Large Scale ◽  
Numerical Study ◽  
Sound Field ◽  
Field Analysis ◽  
Fast Multipole ◽  
Plane Symmetric ◽  
Sound Fields ◽  
Element Method

The fast multipole boundary element method (FMBEM) is an advanced BEM, with which both the operation count and the memory requirements are O(Na log b N) for large-scale problems, where N is the degree of freedom (DOF), a ≥ 1 and b ≥ 0. In this paper, an efficient technique for analyses of plane-symmetric sound fields in the acoustic FMBEM is proposed. Half-space sound fields where an infinite rigid plane exists are typical cases of these fields. When one plane of symmetry is assumed, the number of elements and cells required for the FMBEM with this technique are half of those for the FMBEM used in a naive manner. In consequence, this technique reduces both the computational complexity and the memory requirements for the FMBEM almost by half. The technique is validated with respect to accuracy and efficiency through numerical study.

scholarly journals Effect of Inner Cavity on Radiated Sound Field from a Circular Duct.

2000 ◽  
Vol 66 (649) ◽  
pp. 2364-2369 ◽  
Author(s):  
Yasuji TSUBAKISHITA ◽  
Koichi TANAKA ◽  
Koichi HAYASHI
Keyword(s):  
Sound Field ◽  
Circular Duct ◽  
Radiated Sound

On hydrodynamic and acoustic modes in a ducted shear flow with wall lining

2007 ◽  
Vol 583 ◽  
pp. 45-70 ◽  
Author(s):  
GREGORY G. VILENSKI ◽  
SJOERD W. RIENSTRA
Keyword(s):  
Short Wavelength ◽  
Numerical Study ◽  
Flow Density ◽  
Mean Flow ◽  
Hydrodynamic Modes ◽  
Difficult Situation ◽  
Impedance Boundary ◽  
Circular Duct ◽  
Wall Lining ◽  
Isentropic Flow

The propagation of small-amplitude modes in an inviscid but sheared subsonic mean flow inside a duct is considered. For isentropic flow in a circular duct with zero swirl and constant mean flow density the pressure modes are described in terms of the eigenvalue problem for the Pridmore-Brown equation with Myers' locally reacting impedance boundary conditions.The key purpose of the paper is to extend the results of the numerical study of the spectrum for the case of lined ducts with uniform mean flow in Rienstra (Wave Motion, vol. 37, 2003b, p. 119), in order to examine the effects of the shear and wall lining. In the present paper this far more difficult situation is dealt with analytically. The high-frequency short-wavelength asymptotic solution of the problem based on the WKB method is derived for the acoustic part of the spectrum. Owing to the stiffness of the governing equations, an accurate numerical study of the spectral properties of the problem for mean flows with strong shear proves to be a non-trivial task which deserves separate consideration.The second objective of the paper is to gain theoretical insight into the properties of the hydrodynamic part of the spectrum. An analysis of hydrodynamic modes both in the short-wavelength limit and for the case of the narrow duct is presented. For simplicity, only the hard-wall flow configuration is considered.

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