Descrizione del progetto
Un nuovo approccio della meccanica dei fluidi all’intermittenza delle turbolenze
Un comportamento intermittente è comunemente osservato nei flussi di fluido turbolenti. L’intermittenza della turbolenza sfida i tradizionali approcci geofisici per rappresentare il mescolamento turbolento. Sia le osservazioni sul campo che gli attuali approcci numerici hanno i loro limiti, portando a una mancanza di comprensione a livello di processo dell’intermittenza di turbolenza nello strato limite atmosferico. Il progetto trainABL, finanziato dall’UE, si propone di fornire la prima parametrizzazione di mescolamento turbolento fisicamente coerente che tiene conto dell’importanza dell’intermittenza della turbolenza, copre l’intera gamma verticale dello strato limite atmosferico ed è valida per tutti i regimi di stratificazione. Raggiungerà questo obiettivo adottando un approccio della meccanica dei fluidi al fenomeno geofisico dell’intermittenza della turbolenza nello strato limite atmosferico.
Obiettivo
Vertical exchange in the atmospheric boundary is primarily due to turbulence, but turbulence may cease locally as a consequence of stable density stratification. This state of turbulence intermittency challenges traditional geophysical approaches to represent turbulent mixing. Field observations of the phenomenon are hard to obtain because of broad-scale interacting processes. Existing numerical approaches based on bulk turbulence closures reach their limits because they neglect the relevance of large-scale intermittency for turbulent mixing. Hence, process-level insight to turbulence intermittency in the atmospheric boundary layer is lacking which has dramatic consequences for the forecast of minimum temperature, of frost and fog situations, and of the potential for wind-power extraction.
trainABL recognizes the geophysical phenomenon of turbulence intermittency in the atmospheric boundary layer as a fluid mechanics problem. A virtual-lab approach based on direct numerical simulation yields an appropriate turbulence-resolving representation of the intermittently turbulent atmospheric boundary layer. The quantitative insight into large-scale intermittency offered by direct numerical simulation in combination with large-eddy simulation and observational data allows to transfer the emerging physical understanding to the geophysical range of parameters. This paves the avenue towards a novel turbulence mixing representation based on factorization of the turbulent flux into a reference flux and pre-factor accounting for large-scale intermittency. trainABL will thus provide a first physically consistent turbulent mixing parametrization that acknowledges the importance of turbulence intermittency, covers the entire vertical range of the atmospheric boundary layer, and is valid for all regimes of stratification.
Campo scientifico
Programma(i)
Argomento(i)
Meccanismo di finanziamento
ERC-STG - Starting GrantIstituzione ospitante
14195 Berlin
Germania