Turbulence comes in bursts in stably stratified flows
There is a clear distinction between simple laminar and complex turbulent fluids; however, in some cases, as for the nocturnal planetary boundary layer, a stable and well-ordered flow can develop intense and sporadic bursts of turbulent activity that disappear slowly in time. This phenomenon is ill...
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todo:paper_15393755_v89_n4_p_Rorai2023-10-03T16:22:48Z Turbulence comes in bursts in stably stratified flows Rorai, C. Mininni, P.D. Pouquet, A. Velocity Isotropic turbulent flow Nonlinear amplification Planetary boundary layers Stratified turbulence Temperature fluctuation Turbulent activity Vertical derivatives Vertical velocity Turbulence There is a clear distinction between simple laminar and complex turbulent fluids; however, in some cases, as for the nocturnal planetary boundary layer, a stable and well-ordered flow can develop intense and sporadic bursts of turbulent activity that disappear slowly in time. This phenomenon is ill understood and poorly modeled and yet it is central to our understanding of weather and climate dynamics. We present here data from direct numerical simulations of stratified turbulence on grids of 20483 points that display the somewhat paradoxical result of measurably stronger events for more stable flows, not only in the temperature and vertical velocity derivatives as commonplace in turbulence, but also in the amplitude of the fields themselves, contrary to what happens for homogenous isotropic turbulent flows. A flow visualization suggests that the extreme values take place in Kelvin-Helmoltz overturning events and fronts that develop in the field variables. These results are confirmed by the analysis of a simple model that we present. The model takes into consideration only the vertical velocity and temperature fluctuations and their vertical derivatives. It indicates that in stably stratified turbulence, the stronger bursts can occur when the flow is expected to be more stable. The bursts are generated by a rapid nonlinear amplification of energy stored in waves and are associated with energetic interchanges between vertical velocity and temperature (or density) fluctuations in a range of parameters corresponding to the well-known saturation regime of stratified turbulence. © 2014 American Physical Society. Fil:Mininni, P.D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_15393755_v89_n4_p_Rorai |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
Velocity Isotropic turbulent flow Nonlinear amplification Planetary boundary layers Stratified turbulence Temperature fluctuation Turbulent activity Vertical derivatives Vertical velocity Turbulence |
| spellingShingle |
Velocity Isotropic turbulent flow Nonlinear amplification Planetary boundary layers Stratified turbulence Temperature fluctuation Turbulent activity Vertical derivatives Vertical velocity Turbulence Rorai, C. Mininni, P.D. Pouquet, A. Turbulence comes in bursts in stably stratified flows |
| topic_facet |
Velocity Isotropic turbulent flow Nonlinear amplification Planetary boundary layers Stratified turbulence Temperature fluctuation Turbulent activity Vertical derivatives Vertical velocity Turbulence |
| description |
There is a clear distinction between simple laminar and complex turbulent fluids; however, in some cases, as for the nocturnal planetary boundary layer, a stable and well-ordered flow can develop intense and sporadic bursts of turbulent activity that disappear slowly in time. This phenomenon is ill understood and poorly modeled and yet it is central to our understanding of weather and climate dynamics. We present here data from direct numerical simulations of stratified turbulence on grids of 20483 points that display the somewhat paradoxical result of measurably stronger events for more stable flows, not only in the temperature and vertical velocity derivatives as commonplace in turbulence, but also in the amplitude of the fields themselves, contrary to what happens for homogenous isotropic turbulent flows. A flow visualization suggests that the extreme values take place in Kelvin-Helmoltz overturning events and fronts that develop in the field variables. These results are confirmed by the analysis of a simple model that we present. The model takes into consideration only the vertical velocity and temperature fluctuations and their vertical derivatives. It indicates that in stably stratified turbulence, the stronger bursts can occur when the flow is expected to be more stable. The bursts are generated by a rapid nonlinear amplification of energy stored in waves and are associated with energetic interchanges between vertical velocity and temperature (or density) fluctuations in a range of parameters corresponding to the well-known saturation regime of stratified turbulence. © 2014 American Physical Society. |
| format |
JOUR |
| author |
Rorai, C. Mininni, P.D. Pouquet, A. |
| author_facet |
Rorai, C. Mininni, P.D. Pouquet, A. |
| author_sort |
Rorai, C. |
| title |
Turbulence comes in bursts in stably stratified flows |
| title_short |
Turbulence comes in bursts in stably stratified flows |
| title_full |
Turbulence comes in bursts in stably stratified flows |
| title_fullStr |
Turbulence comes in bursts in stably stratified flows |
| title_full_unstemmed |
Turbulence comes in bursts in stably stratified flows |
| title_sort |
turbulence comes in bursts in stably stratified flows |
| url |
http://hdl.handle.net/20.500.12110/paper_15393755_v89_n4_p_Rorai |
| work_keys_str_mv |
AT roraic turbulencecomesinburstsinstablystratifiedflows AT mininnipd turbulencecomesinburstsinstablystratifiedflows AT pouqueta turbulencecomesinburstsinstablystratifiedflows |
| _version_ |
1807316651608113152 |