Fluctuations of the wall shear stress vector in a large-scale natural convection cell
We report first experimental data of the wall shear stress in turbulent air flow in a large-scale Rayleigh–Bénard experiment. Using a novel, nature-inspired measurement concept [C. H. Bruecker and V. Mikulich, PLoS One 12, e0179253 (2017)], we measured the mean and fluctuating part of the two compon...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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AIP Publishing LLC
2020-07-01
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| Series: | AIP Advances |
| Online Access: | http://dx.doi.org/10.1063/5.0006610 |
| _version_ | 1818334211370647552 |
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| author | R. du Puits C. Bruecker |
| author_facet | R. du Puits C. Bruecker |
| author_sort | R. du Puits |
| collection | DOAJ |
| description | We report first experimental data of the wall shear stress in turbulent air flow in a large-scale Rayleigh–Bénard experiment. Using a novel, nature-inspired measurement concept [C. H. Bruecker and V. Mikulich, PLoS One 12, e0179253 (2017)], we measured the mean and fluctuating part of the two components of the wall shear stress vector at the heated bottom plate at a Rayleigh number Ra = 1.58 × 1010 and a Prandtl number Pr = 0.7. The total sampling period of 1.5 h allowed us to capture the dynamics of the magnitude and the orientation of the vector over several orders of characteristic timescales of the large-scale circulation. We found the amplitude of short-term (turbulent) fluctuations to be following a highly skewed Weibull distribution, while the long-term fluctuations are dominated by the modulation effect of a quasi-regular angular precession of the outer flow around a constant mean, the timescale of which is coupled to the characteristic eddy turnover time of the global recirculation roll. Events of instantaneous negative streamwise wall shear occur when rapid twisting of the local flow happens. A mechanical model is used to explain the precession by tilting the spin moment of the large circulation roll and conservation of angular momentum. A slow angular drift of the mean orientation is observed in a phase of considerable weakening of mean wind magnitude. |
| first_indexed | 2024-12-13T14:03:56Z |
| format | Article |
| id | doaj.art-a1187f997ae44e1784ff9e3b474e2cd5 |
| institution | Directory Open Access Journal |
| issn | 2158-3226 |
| language | English |
| last_indexed | 2024-12-13T14:03:56Z |
| publishDate | 2020-07-01 |
| publisher | AIP Publishing LLC |
| record_format | Article |
| series | AIP Advances |
| spelling | doaj.art-a1187f997ae44e1784ff9e3b474e2cd52022-12-21T23:42:39ZengAIP Publishing LLCAIP Advances2158-32262020-07-01107075105075105-1010.1063/5.0006610Fluctuations of the wall shear stress vector in a large-scale natural convection cellR. du Puits0C. Bruecker1Institute of Thermodynamics and Fluid Mechanics, Technische Universitaet Ilmenau, 98684 Ilmenau, GermanySchool of Mathematics, Computer Science and Engineering, City, University of London, London EC1V 0HB, United KingdomWe report first experimental data of the wall shear stress in turbulent air flow in a large-scale Rayleigh–Bénard experiment. Using a novel, nature-inspired measurement concept [C. H. Bruecker and V. Mikulich, PLoS One 12, e0179253 (2017)], we measured the mean and fluctuating part of the two components of the wall shear stress vector at the heated bottom plate at a Rayleigh number Ra = 1.58 × 1010 and a Prandtl number Pr = 0.7. The total sampling period of 1.5 h allowed us to capture the dynamics of the magnitude and the orientation of the vector over several orders of characteristic timescales of the large-scale circulation. We found the amplitude of short-term (turbulent) fluctuations to be following a highly skewed Weibull distribution, while the long-term fluctuations are dominated by the modulation effect of a quasi-regular angular precession of the outer flow around a constant mean, the timescale of which is coupled to the characteristic eddy turnover time of the global recirculation roll. Events of instantaneous negative streamwise wall shear occur when rapid twisting of the local flow happens. A mechanical model is used to explain the precession by tilting the spin moment of the large circulation roll and conservation of angular momentum. A slow angular drift of the mean orientation is observed in a phase of considerable weakening of mean wind magnitude.http://dx.doi.org/10.1063/5.0006610 |
| spellingShingle | R. du Puits C. Bruecker Fluctuations of the wall shear stress vector in a large-scale natural convection cell AIP Advances |
| title | Fluctuations of the wall shear stress vector in a large-scale natural convection cell |
| title_full | Fluctuations of the wall shear stress vector in a large-scale natural convection cell |
| title_fullStr | Fluctuations of the wall shear stress vector in a large-scale natural convection cell |
| title_full_unstemmed | Fluctuations of the wall shear stress vector in a large-scale natural convection cell |
| title_short | Fluctuations of the wall shear stress vector in a large-scale natural convection cell |
| title_sort | fluctuations of the wall shear stress vector in a large scale natural convection cell |
| url | http://dx.doi.org/10.1063/5.0006610 |
| work_keys_str_mv | AT rdupuits fluctuationsofthewallshearstressvectorinalargescalenaturalconvectioncell AT cbruecker fluctuationsofthewallshearstressvectorinalargescalenaturalconvectioncell |