Rayleigh-Plateau Dissipative Instability
The instability of a freely falling jet of liquid in air taking into account the viscosity of the contacting media is considered. In neglecting the viscosities of both media, instability was studied by Rayleigh and Plateau. They showed that instability develops as a result of the action of surface f...
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| Format: | Article |
| Language: | English |
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V.N. Karazin Kharkiv National University Publishing
2020-04-01
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| Series: | East European Journal of Physics |
| Subjects: | |
| Online Access: | https://periodicals.karazin.ua/eejp/article/view/15548 |
| _version_ | 1811225596483600384 |
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| author | Oksana L. Andreeva Leonid A. Bulavin Viktor I. Tkachenko |
| author_facet | Oksana L. Andreeva Leonid A. Bulavin Viktor I. Tkachenko |
| author_sort | Oksana L. Andreeva |
| collection | DOAJ |
| description | The instability of a freely falling jet of liquid in air taking into account the viscosity of the contacting media is considered. In neglecting the viscosities of both media, instability was studied by Rayleigh and Plateau. They showed that instability develops as a result of the action of surface forces, and is expressed in a change in the cylindrical shape of the boundary of a freely falling jet of liquid with air into a sequence of spherical drops. In subsequent works, by phenomenological consideration of viscosity by means of the Ohnesorge number, it is shown that the viscosity of each of the contacting media affects the nature of the instability. However, this method of taking viscosity into account is not entirely correct, because does not take into account the specificity of the boundary conditions existing at the interface. It is proposed to use percolation boundary conditions, the validity of which is proved by the example of the exact determination of the threshold velocity of occurrence of Kelvin-Helmholtz instability. A dispersion equation of the Rayleigh-Plateau problem with percolation boundary conditions that describes the instability taking into account the viscosity of both media is obtained. The dissipative nature of the development of such instabilities is substantiated. The growth rates of instabilities are determined in cases when: the jet and medium have a low viscosity (ideal fluids); the jet is characterized by high viscosity, and the environment is small; the jet and the environment are highly viscous. It is shown that the theoretical model of droplet decay of the jet in the absence of viscosity of both media is quite good, in quantitative terms, consistent with experimental results. The maximum increment is equal γmaxKGγ≈0.32, against the Rayleigh-Plateau increment γmaxKGγ≈0.34, for disturbances with the same wave number XMAX≈0.37. It was also shown that for viscous jets and a weakly viscous environment, the instability increment describes the experimental results with a rather high degree of accuracy. Numerical calculations show that for jets of comparable viscosity, the instability increment decreases with increasing viscosity of the environment. If the viscosity of the environment is constant, then the increment of instability will be greater where the viscosity of the stream is higher. It is shown that the results of theoretical calculations are in good agreement with the available experimental data. |
| first_indexed | 2024-04-12T09:10:00Z |
| format | Article |
| id | doaj.art-0421e8da08d04ff381659b575352e80a |
| institution | Directory Open Access Journal |
| issn | 2312-4334 2312-4539 |
| language | English |
| last_indexed | 2024-04-12T09:10:00Z |
| publishDate | 2020-04-01 |
| publisher | V.N. Karazin Kharkiv National University Publishing |
| record_format | Article |
| series | East European Journal of Physics |
| spelling | doaj.art-0421e8da08d04ff381659b575352e80a2022-12-22T03:39:00ZengV.N. Karazin Kharkiv National University PublishingEast European Journal of Physics2312-43342312-45392020-04-012384710.26565/2312-4334-2020-2-0215548Rayleigh-Plateau Dissipative InstabilityOksana L. Andreeva0Leonid A. Bulavin1Viktor I. Tkachenko2National Science Center “Kharkov Institute of Physics and Technology”, Kharkiv, UkraineTaras Shevchenko National University of Kyiv, Kyiv, UkraineNational Science Center “Kharkov Institute of Physics and Technology”, Kharkiv, Ukraine; V.N. Karazin Kharkiv National University, Kharkiv, UkraineThe instability of a freely falling jet of liquid in air taking into account the viscosity of the contacting media is considered. In neglecting the viscosities of both media, instability was studied by Rayleigh and Plateau. They showed that instability develops as a result of the action of surface forces, and is expressed in a change in the cylindrical shape of the boundary of a freely falling jet of liquid with air into a sequence of spherical drops. In subsequent works, by phenomenological consideration of viscosity by means of the Ohnesorge number, it is shown that the viscosity of each of the contacting media affects the nature of the instability. However, this method of taking viscosity into account is not entirely correct, because does not take into account the specificity of the boundary conditions existing at the interface. It is proposed to use percolation boundary conditions, the validity of which is proved by the example of the exact determination of the threshold velocity of occurrence of Kelvin-Helmholtz instability. A dispersion equation of the Rayleigh-Plateau problem with percolation boundary conditions that describes the instability taking into account the viscosity of both media is obtained. The dissipative nature of the development of such instabilities is substantiated. The growth rates of instabilities are determined in cases when: the jet and medium have a low viscosity (ideal fluids); the jet is characterized by high viscosity, and the environment is small; the jet and the environment are highly viscous. It is shown that the theoretical model of droplet decay of the jet in the absence of viscosity of both media is quite good, in quantitative terms, consistent with experimental results. The maximum increment is equal γmaxKGγ≈0.32, against the Rayleigh-Plateau increment γmaxKGγ≈0.34, for disturbances with the same wave number XMAX≈0.37. It was also shown that for viscous jets and a weakly viscous environment, the instability increment describes the experimental results with a rather high degree of accuracy. Numerical calculations show that for jets of comparable viscosity, the instability increment decreases with increasing viscosity of the environment. If the viscosity of the environment is constant, then the increment of instability will be greater where the viscosity of the stream is higher. It is shown that the results of theoretical calculations are in good agreement with the available experimental data.https://periodicals.karazin.ua/eejp/article/view/15548rayleigh-plateau instabilitysurface tensionviscositypercolation boundary conditionsdissipative instabilityinstability incrementwave numberinstability range |
| spellingShingle | Oksana L. Andreeva Leonid A. Bulavin Viktor I. Tkachenko Rayleigh-Plateau Dissipative Instability East European Journal of Physics rayleigh-plateau instability surface tension viscosity percolation boundary conditions dissipative instability instability increment wave number instability range |
| title | Rayleigh-Plateau Dissipative Instability |
| title_full | Rayleigh-Plateau Dissipative Instability |
| title_fullStr | Rayleigh-Plateau Dissipative Instability |
| title_full_unstemmed | Rayleigh-Plateau Dissipative Instability |
| title_short | Rayleigh-Plateau Dissipative Instability |
| title_sort | rayleigh plateau dissipative instability |
| topic | rayleigh-plateau instability surface tension viscosity percolation boundary conditions dissipative instability instability increment wave number instability range |
| url | https://periodicals.karazin.ua/eejp/article/view/15548 |
| work_keys_str_mv | AT oksanalandreeva rayleighplateaudissipativeinstability AT leonidabulavin rayleighplateaudissipativeinstability AT viktoritkachenko rayleighplateaudissipativeinstability |