A Proper Orthogonal Decomposition Analysis to Identify the Dominant Modes of the Steady State Acoustic Pressure Field in a Cavity

2003 ◽  
Author(s):  
Ioannis T. Georgiou ◽  
Christos I. Papadopoulos
Keyword(s):  
Steady State ◽  
Proper Orthogonal Decomposition ◽  
Sound Pressure ◽  
Acoustic Pressure ◽  
Pressure Field ◽  
Decomposition Analysis ◽  
Orthogonal Decomposition ◽  
Harmonic Source ◽  
Proper Orthogonal ◽  
Identification Tool

The technique of Proper Orthogonal Decomposition (POD) has been used to develop an identification tool to analyze steady state dynamics in acoustics. The information on the dynamics needed for the POD technique is obtained by solving numerically with the method of finite elements the wave equation inside a cavity. The POD technique identifies optimum spatial patterns it terms of Proper Orthogonal Modes. The steady state sound pressure field in a cavity excited by a single harmonic source responds with a very small number of POD modes. Under certain forcing conditions, the POD modes are identical to the Fourier acoustic modes. The POD technique of Proper Orthogonal Decomposition (POD) proves to be a very effective identification tool.

On Proper Orthogonal Decomposition or K-L Expansion to Analyze Transient Sound Pressure Fields in Linear Acoustics

2003 ◽  
Author(s):  
Ioannis T. Georgiou ◽  
Christos I. Papadopoulos
Keyword(s):  
Proper Orthogonal Decomposition ◽  
Sound Pressure ◽  
Pressure Field ◽  
Low Frequency ◽  
Temporal Patterns ◽  
Orthogonal Decomposition ◽  
Noise Sources ◽  
Air Cavity ◽  
Spatio Temporal ◽  
Proper Orthogonal

Identification of the most energetic spatio-temporal patterns that govern the low-frequency dynamics of an air cavity excited by noise sources could lead to significant design improvements of enclosures for noise reduction / isolation and / or sound quality. In this work we show how the Proper Orthogonal Decomposition (POD) method can be applied to identify optimum spatio-temporal patterns governing the dynamics of the sound pressure field developed inside an air cavity. The novel feature of this approach resides into the fact that the POD technique is utilized to process databases for acoustic variables produced by state of the art computational methods in acoustics, such as the finite element method. For a cavity with rigid walls and excited by a harmonic point source, the POD technique reveals that the sound pressure field is composed of a very small number of Proper Orthogonal Modes, which are unique since they are optimum by construction. The POD technique identifies the shapes or patterns of these modes.

Analysis of Door Mirror Aeroacoustic Source Using Extended Proper Orthogonal Decomposition

2010 ◽  
Author(s):  
Abbas Hekmati ◽  
Denis Ricot ◽  
Philippe Druault
Keyword(s):  
Proper Orthogonal Decomposition ◽  
Acoustic Pressure ◽  
Pressure Field ◽  
Air Flow ◽  
Orthogonal Decomposition ◽  
3D Simulation ◽  
Aerodynamic Pressure ◽  
Threshold Determination ◽  
Classical Formulation ◽  
Proper Orthogonal

Based on a 3D simulation of the air flow around a vehicle, the Extended Proper Orthogonal Decomposition (EPOD) is employed in order to identify the existing relation between aerodynamic events around the door mirror (Ω domain) and the near acoustic pressure field (S domain). The aerodynamic pressure field on a 2D plan of Ω is decomposed using a classical formulation of POD. These modes are then sorted according to their correlation to the acoustic pressure field. The modes for which this correlation value is higher than a given threshold are selected. The proposed threshold determination is detailed. The selected modes are then employed in an EPOD procedure in order to determine their contribution to the acoustic pressure field. The aerodynamic pressure field reconstructed by these selected modes has a good correlation with the acoustic pressure field. This correlation is higher than the correlation between the aerodynamic pressure field reconstructed by the most energetic modes and the acoustic pressure field.

Applying Proper Orthogonal Decomposition Tools for Modal Identification of Coupled Structural-Acoustic Dynamic Fields

2004 ◽  
Author(s):  
Ioannis T. Georgiou ◽  
Christos I. Papadopoulos ◽  
Dimitris P. Servis
Keyword(s):  
Finite Element ◽  
Proper Orthogonal Decomposition ◽  
Sound Pressure ◽  
Coupled System ◽  
Orthogonal Decomposition ◽  
Modal Identification ◽  
Interaction Dynamics ◽  
Element Simulation ◽  
Proper Orthogonal ◽  
Identification Tool

To characterize the modal structure of the interaction dynamics of plate-like structures functioning as sound reducing systems, we apply the method of Proper Orthogonal Decomposition (POD) to analyze the dynamics of a room-plate-room coupled system. Given the finite element simulation as information on the dynamic response of this coupled system, it is shown that the POD technique identifies unique, optimum spatial patterns (modes) for all dynamic fields such as the sound pressure in the rooms and especially the vibration response of the plate. The Proper Orthogonal Decomposition (POD) technique proves to be a very effective identification tool for structural-acoustical systems.

Study on flow field and aerodynamic noise of electric vehicle rearview mirror

2021 ◽  
pp. 095440702110228
Author(s):  
Xiaowei Hao ◽  
Zhigang Yang ◽  
Qiliang Li
Keyword(s):  
Flow Field ◽  
Proper Orthogonal Decomposition ◽  
Electric Vehicle ◽  
Sound Pressure ◽  
Pressure Level ◽  
Orthogonal Decomposition ◽  
Aerodynamic Noise ◽  
Turbulent Pressure ◽  
Rearview Mirror ◽  
Proper Orthogonal

With the development of new energy and intelligent vehicles, aerodynamic noise problem of pure electric vehicles at high speed has become increasingly prominent. The characteristics of the flow field and aerodynamic noise of the rearview mirror region were investigated by large eddy simulation, acoustic perturbation equations and reduction order analysis. By comparing the pressure coefficients of the coarse, medium and dense grids with wind tunnel test results, the pressure distribution, and numerical accuracy of the medium grid on the body are clarified. It is shown from the flow field proper orthogonal decomposition of the mid-section that the sum of the energy of the first three modes accounts for more than 16%. Based on spectral proper orthogonal decomposition, the peak frequencies of the first-order mode are 19 and 97 Hz. As for the turbulent pressure of side window, the first mode accounts for approximately 11.3% of the total energy, and its peak appears at 39 and 117 Hz. While the first mode of sound pressure accounts for about 41.7%, and the energy peaks occur at 410 and 546 Hz. Compared with traditional vehicle, less total turbulent pressure level and total sound pressure level are found at current electric vehicle because of the limited interaction between the rearview mirror and A-pillar.

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