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An Acoustics Intensity Based Investigation οf the Energy Flow Over the Barriers

100%

Weyna S.

Acta Physica Polonica A

2010

vol. 118

issue 1

172-178

Many of theoretical research of the acoustics fields provides useful information about pressure fields, but none currently offers a full mapping of the acoustic energy flow (vectorial effects) in front and back of any scattering systems working in 3D real environmental conditions. Interference, diffraction and scattering of waves made the real field very complex and difficult to the theoretical modelling. This is one of the reasons why the experimental investigations of acoustic fields using sound intensity (SI) technique are so effective and serviceable methods. The visualization of acoustic energy flow in real-life acoustic 3D space fields can explain many particulars energetic effects (perturbations and vortex flow, effects of scattering in direct and near field, etc.), concerning the areas in which it is difficult to make numerical modeling and analysis with the CFD-FSI-CAA simulation methods. The sound intensity image represents a more accurate and efficient information compare to the spatial sound fields modelled. The article presents the application of SI technique to graphic presentation of spatial distribution the acoustic energy flow over the barriers of various geometrical shapes structures located in a three-dimensional space. As the results of research, the graphic analysis of the sound intensity flux in 2D and 3D space is show. Visualisation of research results is shown in the form of intensity streamlines in space and as a shape of flow wave or isosurface in three-dimensional space. Numerous examples illustrate the application of the SI measurement for practical problems at the vibroacoustical diagnostic and noise abatement, as well as to the validation of results of CFD/CAA numerical modelling. The differences, if appearance, mainly result from the fact that theoretical forecasting uses far too big simplifications or that it is impossible to obtain proper data on real physical features of the tested area and structures.

Phase-Locked Particle Image Velocimetry Visualization of the Sound Field at the Outlet of a Circular Tube

63%

Weyna S., Mickiewicz W.

Acta Physica Polonica A

2014

vol. 125

issue 4A

A-108-A-112

The shedding process and acoustic flow formation in the region of outlet of a cylinder duct has been investigated by means of the particle image velocimetry (PIV) technique. The research work on the behavior of the sound field at outlets of waveguides addresses issues of importance to industrial applications. The obtained results can be used in a number of industrial applications involving pipes, ducts and tubing. In our investigation the acoustics flow fields are measured with a phase-locked PIV system with high sampling rate and large internal memory block using DAVIS v. 8.11 software. A cross-correlation method, in conjunction with the FFT analysis, is used as a vector processing algorithm. A series of PIV vector maps was used to evaluate the acoustic velocity field at the open end of circular tube throughout the acoustic cycle for frequencies of 700 Hz and 1400 Hz. Six phase steps were assumed for one frequency cycle and the characteristic signal was extracted from the velocity data step and shown graphically.

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2 Acta Physica Polonica A

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1 2010

2 Weyna S.

1 Mickiewicz W.

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An Acoustics Intensity Based Investigation οf the Energy Flow Over the Barriers

Phase-Locked Particle Image Velocimetry Visualization of the Sound Field at the Outlet of a Circular Tube