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Generalized wave envelope analysis of sound propagation in ducts with stepped noise source profiles and variable axial impedance
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Baumeister, K. J. |
| Copyright Year | 1975 |
| Description | A finite difference formulation is presented for sound propagation in a rectangular two-dimensional duct without steady flow. Before the difference equations are formulated, the governing Helmholtz equation is first transformed to a form whose solution tends not to oscillate along the length of the duct. This transformation reduces the required number of grid points by an order of magnitude. Example solutions indicate that stepped noise source profiles have much higher attenuation than plane waves in a uniform impedance liner. Also, multiple stepped impedance liners are shown to have higher attenuation than uniform ducts if the impedances are chosen properly. For optimum noise reduction with axial variations in impedance, the numerical analysis indicates that for a plane wave input the resistance should be near zero at the entrance of a suppressor duct, while the reactance should be near the optimum value associated with the least-attenuated mode in a uniform duct. |
| File Size | 501163 |
| Page Count | 16 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19750009957 |
| Archival Resource Key | ark:/13960/t6f23qx3j |
| Language | English |
| Publisher Date | 1975-01-01 |
| Access Restriction | Open |
| Subject Keyword | Acoustics Ducted Flow Numerical Analysis Sound Propagation Acoustic Measurement Acoustic Properties Mathematical Models Two Dimensional Flow Noise Spectra Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
