Flow patterns and noise of a choked gas jet expanding into a duct
Axi-symmetric, choked air outflow into a duct with an abrupt enlargement of its cross-section was investigated in order to establish the relations between the flow pattern and the aerodynamic noise generated. Four main kinds of flow structure, possessing different acoustic properties, were found in...
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| Format: | Article |
| Language: | English |
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Institute of Fundamental Technological Research Polish Academy of Sciences
2016-03-01
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| Series: | Archives of Acoustics |
| Online Access: | https://acoustics.ippt.pan.pl/index.php/aa/article/view/3513 |
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| author | Krystyna J. WITCZAK |
| author_facet | Krystyna J. WITCZAK |
| author_sort | Krystyna J. WITCZAK |
| collection | DOAJ |
| description | Axi-symmetric, choked air outflow into a duct with an abrupt enlargement of its cross-section was investigated in order to establish the relations between the flow pattern and the aerodynamic noise generated. Four main kinds of flow structure, possessing different acoustic properties, were found in the cases studied of the outflow from convergent circular and annular nozzles. These patterns correspond to the occurrence of: cellular structure, self-excited oscillations, single shock wave (noise minimum) and supersonic flow. An acoustic feedback type source of sound can appear under certain circumstances in the cellular structure. The self-excited shock wave and pressure oscillations produce noise characterized by discrete frequencies in the sound pressure level spectrum. The reasons for the minimum noise generation, which takes place before the reattachment of the supersonic stream boundary to the duct wall, are explained. Prevention of strong oscillations by the insertion of spoilers at the nozzle lip reduces the noise significantly over a wide range of supply pressures, however it increases the noise minimum due to turbulence intensity growth. Recommendations for nozzle and duct geometry for noise reduction are given. |
| format | Article |
| id | doaj-art-eca39ea794dd420db8d8f6e82d15f421 |
| institution | Kabale University |
| issn | 0137-5075 2300-262X |
| language | English |
| publishDate | 2016-03-01 |
| publisher | Institute of Fundamental Technological Research Polish Academy of Sciences |
| record_format | Article |
| series | Archives of Acoustics |
| spelling | doaj-art-eca39ea794dd420db8d8f6e82d15f4212025-08-20T03:25:26ZengInstitute of Fundamental Technological Research Polish Academy of SciencesArchives of Acoustics0137-50752300-262X2016-03-0113Flow patterns and noise of a choked gas jet expanding into a ductKrystyna J. WITCZAK0Warsaw Technical UniversityAxi-symmetric, choked air outflow into a duct with an abrupt enlargement of its cross-section was investigated in order to establish the relations between the flow pattern and the aerodynamic noise generated. Four main kinds of flow structure, possessing different acoustic properties, were found in the cases studied of the outflow from convergent circular and annular nozzles. These patterns correspond to the occurrence of: cellular structure, self-excited oscillations, single shock wave (noise minimum) and supersonic flow. An acoustic feedback type source of sound can appear under certain circumstances in the cellular structure. The self-excited shock wave and pressure oscillations produce noise characterized by discrete frequencies in the sound pressure level spectrum. The reasons for the minimum noise generation, which takes place before the reattachment of the supersonic stream boundary to the duct wall, are explained. Prevention of strong oscillations by the insertion of spoilers at the nozzle lip reduces the noise significantly over a wide range of supply pressures, however it increases the noise minimum due to turbulence intensity growth. Recommendations for nozzle and duct geometry for noise reduction are given.https://acoustics.ippt.pan.pl/index.php/aa/article/view/3513 |
| spellingShingle | Krystyna J. WITCZAK Flow patterns and noise of a choked gas jet expanding into a duct Archives of Acoustics |
| title | Flow patterns and noise of a choked gas jet expanding into a duct |
| title_full | Flow patterns and noise of a choked gas jet expanding into a duct |
| title_fullStr | Flow patterns and noise of a choked gas jet expanding into a duct |
| title_full_unstemmed | Flow patterns and noise of a choked gas jet expanding into a duct |
| title_short | Flow patterns and noise of a choked gas jet expanding into a duct |
| title_sort | flow patterns and noise of a choked gas jet expanding into a duct |
| url | https://acoustics.ippt.pan.pl/index.php/aa/article/view/3513 |
| work_keys_str_mv | AT krystynajwitczak flowpatternsandnoiseofachokedgasjetexpandingintoaduct |