The object of the present work is the study of synthetic turbulence generators for Large Eddy Simulations (LES) and their application to the onshore (high turbulence) conditions used at the PoliMi Wind Tunnel for reproducing the Atmospheric Boundary Layer. This study can be used for optimizing turbulent inflow boundary conditions for the simulations of wind-structure interactions experimentally studied in the PoliMi Wind Tunnel. Different synthetic generators are presented and categorized. Three of them have been chosen and implemented in the numerical framework OpenFOAM. Before treating the Wind Tunnel's chamber geometry set-up, the synthetic generators have been applied to the plane channel flow. The results obtained from these prior simulations have been compared with Direct Numerical Simulations in order to investigate their performance and to set the generators' parameters. Moreover they turned out to be useful in order to validate the meshes and to chose the most suitable turbulence model. The synthetic generators have been then applied to the PoliMi Wind Tunnel set-up. The comparison was made both with a fully developed flow subject to the same conditions, and with the experimental results achieved in the wind tunnel. The goal of the first comparison was to verify the space convergence introduced by these inflow conditions. Due to computational power limitations, the mesh employed was not able to fully resolve the boundary layer. Moreover the used turbulence model had to be chosen more for its robustness than its precision. Despite these limitations, the numerical results have proven to be in satisfactory agreement with the experimental ones, in particular with the most recent synthetic generator.
L’obiettivo di questa tesi è lo studio dei generatori sintetici di turbolenza per le simulazioni a grandi vortici e la loro applicazione al trattamento del set-up della Galelleria del Vento del Politecnico di Milano per la riproduzione dello strato limite atmosferico. Questo studio può essere utilizzato per l'impostazione di condizioni di inflow turbolente per le simulazioni di interazioni vento-struttura studiate sperimentalmente nella Galleria del Vento del PoliMi. Vari generatori di turbolenza sono presentati e classificati e tra questi tre sono stati scelti ed implementati nel framework numerico OpenFOAM con il quale abbiamo effettuato le simulazioni. Prima di trattare la geometria della galleria del vento, il modello è stato applicato ad un caso test: il canale piano. I risultati sono stati confrontati con le Simulazioni Numeriche Dirette (DNS) per convalidare le performances dei tre generatori e trovare valori per i parametri che caratterizzano questi creatori di turbolenza in inlet. Sono inoltre stati utili per validare le griglie di calcolo nonchè i modelli di turbolenza da utilizzare. Tre generatori sintetici sono stati quindi applicati alla geometria della Galleria del Vento. I risultati ottenuti sono quindi stati confrontati sia con i profili ottenuti nelle stesse condizioni da un flusso completamente sviluppato e infine con i risultati ottenuti sperimentalmente in galleria del vento. L'obbiettivo del primo confronto era quello di verificare la dichiarazione teorica secondo cui i generatori sintetici dovrebbero velocizzare la convergenza spaziale di un flusso. A causa di limitazioni in termini di potenza computazionale, la mesh utilizzata non è stata in grado di risolvere interamente lo strato limite ed inoltre il modello di turbolenza è stato scelto più per la sua robustezza che per la sua precisione. Nonostante queste limitazioni i risultati si sono dimostrati in soddisfacente accordo con quelli sperimentali, in particolare con il generatore sintetico di più recente sviluppo.
Synthetic methods for inlet boundary conditions in large eddy simulations : application to PoliMi wind tunnel
DAMIA, CHIARA
2020/2021
Abstract
The object of the present work is the study of synthetic turbulence generators for Large Eddy Simulations (LES) and their application to the onshore (high turbulence) conditions used at the PoliMi Wind Tunnel for reproducing the Atmospheric Boundary Layer. This study can be used for optimizing turbulent inflow boundary conditions for the simulations of wind-structure interactions experimentally studied in the PoliMi Wind Tunnel. Different synthetic generators are presented and categorized. Three of them have been chosen and implemented in the numerical framework OpenFOAM. Before treating the Wind Tunnel's chamber geometry set-up, the synthetic generators have been applied to the plane channel flow. The results obtained from these prior simulations have been compared with Direct Numerical Simulations in order to investigate their performance and to set the generators' parameters. Moreover they turned out to be useful in order to validate the meshes and to chose the most suitable turbulence model. The synthetic generators have been then applied to the PoliMi Wind Tunnel set-up. The comparison was made both with a fully developed flow subject to the same conditions, and with the experimental results achieved in the wind tunnel. The goal of the first comparison was to verify the space convergence introduced by these inflow conditions. Due to computational power limitations, the mesh employed was not able to fully resolve the boundary layer. Moreover the used turbulence model had to be chosen more for its robustness than its precision. Despite these limitations, the numerical results have proven to be in satisfactory agreement with the experimental ones, in particular with the most recent synthetic generator.| File | Dimensione | Formato | |
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Descrizione: Synthetic methods for inlet boundary conditions in Large Eddy Simulations: application to PoliMi Wind Tunnel
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https://hdl.handle.net/10589/175437