Turbulent Superstructures in Inert Jets and Diffusion Jet Flames
An experimental study of spatially localized very large-scale motion superstructures, propagating in a jet of carbon dioxide at low Reynolds numbers, was carried out. A hot-wire anemometer and a high-speed 2D PIV with a frequency of 7 kHz were used as measuring instruments. Such a puff-type superstr...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-12-01
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| Series: | Fluids |
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| Online Access: | https://www.mdpi.com/2311-5521/6/12/459 |
| _version_ | 1797504774617169920 |
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| author | Vadim Lemanov Vladimir Lukashov Konstantin Sharov |
| author_facet | Vadim Lemanov Vladimir Lukashov Konstantin Sharov |
| author_sort | Vadim Lemanov |
| collection | DOAJ |
| description | An experimental study of spatially localized very large-scale motion superstructures, propagating in a jet of carbon dioxide at low Reynolds numbers, was carried out. A hot-wire anemometer and a high-speed 2D PIV with a frequency of 7 kHz were used as measuring instruments. Such a puff-type superstructure in a jet with a longitudinal dimension of up to 20–30 nozzle diameters are initially formed in the jet source—a long tube in a laminar-turbulent transition mode (without artificial disturbances). It is shown that this regime with intermittency in time, when part of the time flow is laminar and the other part of time is turbulent, exists both at the exit from the nozzle and in the near field of the jet. Thus, the structural stability of such turbulent superstructures in the near field of the jet was found. Despite the large longitudinal scale, these formations have a transverse dimension of the order of several nozzle diameters. These structures have a complex internal topology, that is, superstructures are a conglomeration of vortices of different sizes from macroscale to microscale. Using the example of diffusion combustion of methane in air, it is demonstrated that in reacting jets, the existence of such large localized perturbations is a powerful physical mechanism for a global change in the flame topology. At the same time, the presence of a cascade of vortices of different sizes in the puff composition can lead to fractal deformation of the flame front. |
| first_indexed | 2024-03-10T04:09:09Z |
| format | Article |
| id | doaj.art-6446752a87654e04ab2c0a1feec730f3 |
| institution | Directory Open Access Journal |
| issn | 2311-5521 |
| language | English |
| last_indexed | 2024-03-10T04:09:09Z |
| publishDate | 2021-12-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Fluids |
| spelling | doaj.art-6446752a87654e04ab2c0a1feec730f32023-11-23T08:15:48ZengMDPI AGFluids2311-55212021-12-0161245910.3390/fluids6120459Turbulent Superstructures in Inert Jets and Diffusion Jet FlamesVadim Lemanov0Vladimir Lukashov1Konstantin Sharov2Kutateladze Institute of Thermophysics SB RAS, Lavrentieva Ave. 1, Novosibirsk 630090, RussiaKutateladze Institute of Thermophysics SB RAS, Lavrentieva Ave. 1, Novosibirsk 630090, RussiaKutateladze Institute of Thermophysics SB RAS, Lavrentieva Ave. 1, Novosibirsk 630090, RussiaAn experimental study of spatially localized very large-scale motion superstructures, propagating in a jet of carbon dioxide at low Reynolds numbers, was carried out. A hot-wire anemometer and a high-speed 2D PIV with a frequency of 7 kHz were used as measuring instruments. Such a puff-type superstructure in a jet with a longitudinal dimension of up to 20–30 nozzle diameters are initially formed in the jet source—a long tube in a laminar-turbulent transition mode (without artificial disturbances). It is shown that this regime with intermittency in time, when part of the time flow is laminar and the other part of time is turbulent, exists both at the exit from the nozzle and in the near field of the jet. Thus, the structural stability of such turbulent superstructures in the near field of the jet was found. Despite the large longitudinal scale, these formations have a transverse dimension of the order of several nozzle diameters. These structures have a complex internal topology, that is, superstructures are a conglomeration of vortices of different sizes from macroscale to microscale. Using the example of diffusion combustion of methane in air, it is demonstrated that in reacting jets, the existence of such large localized perturbations is a powerful physical mechanism for a global change in the flame topology. At the same time, the presence of a cascade of vortices of different sizes in the puff composition can lead to fractal deformation of the flame front.https://www.mdpi.com/2311-5521/6/12/459pipe gas jetsintermittent transition to turbulencevery large-scale motionsuperstructurespuffsautocorrelation function |
| spellingShingle | Vadim Lemanov Vladimir Lukashov Konstantin Sharov Turbulent Superstructures in Inert Jets and Diffusion Jet Flames Fluids pipe gas jets intermittent transition to turbulence very large-scale motion superstructures puffs autocorrelation function |
| title | Turbulent Superstructures in Inert Jets and Diffusion Jet Flames |
| title_full | Turbulent Superstructures in Inert Jets and Diffusion Jet Flames |
| title_fullStr | Turbulent Superstructures in Inert Jets and Diffusion Jet Flames |
| title_full_unstemmed | Turbulent Superstructures in Inert Jets and Diffusion Jet Flames |
| title_short | Turbulent Superstructures in Inert Jets and Diffusion Jet Flames |
| title_sort | turbulent superstructures in inert jets and diffusion jet flames |
| topic | pipe gas jets intermittent transition to turbulence very large-scale motion superstructures puffs autocorrelation function |
| url | https://www.mdpi.com/2311-5521/6/12/459 |
| work_keys_str_mv | AT vadimlemanov turbulentsuperstructuresininertjetsanddiffusionjetflames AT vladimirlukashov turbulentsuperstructuresininertjetsanddiffusionjetflames AT konstantinsharov turbulentsuperstructuresininertjetsanddiffusionjetflames |