This work deals with the characterization, in terms of operating conditions, of the H3 hypersonic wind tunnel of the Von Karman Institute for Fluid Dynamics (VKI) and with the following operation of the facility for the experimental study of the interaction between the boundary layer and the ablation process of low temperature ablative materials. For the characterization of the H3 facility, first, a new calibration of the flow field has been performed by using a pitot rake, for operating conditions ranging wider extremes values than previous calibrations. After CFD analyses of the diffuser-ejector system have been carried out, an experimental test campaign has been performed in order to validate the CFD analyses and completely characterize the facility operation in free stream condition. Then, it followed a series of experiments with models of increasing size and different shapes in order to determine the blockage effect on the operation of the hypersonic wind tunnel. The following operation of the facility was aimed to study the boundary layer interaction with the ablative process on low temperature ablative models. First these models have been built after having appropriately designed the sintering system. Secondly, we have applied the Planar Laser Induced Fluorescence method to visualize the flow behavior on these naphthalene models: a laminar-turbulent transition due to the ablation process has been observed together with the main flow structures.
Il presente lavoro di tesi riguarda la caratterizzazione, in termini di condizioni operative, della galleria del vento ipersonica H3 del Von Karman Institute for Fluid Dynamics (VKI) e la seguente operazione della struttura per lo studio sperimentale dell'interazione tra lo strato limite e il processo di ablazione di materiali ablativi a bassa temperatura. Per la caratterizzazione della galleria del vento H3 è stata innanzitutto eseguita una nuova calibrazione del flusso utilizzando un Pitot rake per condizioni operative più ampie rispetto alle precedenti calibrazioni. Dopo l'analisi CFD del sistema diffusore - ejector, è stata condotta una campagna di test sperimentale per validare le analisi CFD e caratterizzare completamente l'operazione dell'impianto in condizioni di flusso libero. In seguito, sono stati condotti una serie di esperimenti con modelli di dimensioni crescenti e forme diverse per determinare l'effetto del bloccaggio sul funzionamento della galleria del vento ipersonica. Il successivo utilizzo della struttura era finalizzata a studiare l'interazione dello strato limite con il processo ablativo su modelli ablativi a bassa temperatura. In primo luogo, questi modelli sono stati costruiti dopo aver progettato appropriatamente il sistema di sinterizzazione. In secondo luogo, il metodo PLIF (Planar Laser Induced Fluorescence) è stato applicato per visualizzare il comportamento del flusso su questi modelli di naftalina: è stato possibile osservare una transizione da laminare a turbolento dovuta al processo di ablazione insieme alle principali strutture del flusso.
Experimental study of hypersonic flow in the VKI H3 wind tunnel : from facility characterization to boundary-layer interaction over low-temperature ablators
AGOSTINELLI, PASQUALE WALTER
2017/2018
Abstract
This work deals with the characterization, in terms of operating conditions, of the H3 hypersonic wind tunnel of the Von Karman Institute for Fluid Dynamics (VKI) and with the following operation of the facility for the experimental study of the interaction between the boundary layer and the ablation process of low temperature ablative materials. For the characterization of the H3 facility, first, a new calibration of the flow field has been performed by using a pitot rake, for operating conditions ranging wider extremes values than previous calibrations. After CFD analyses of the diffuser-ejector system have been carried out, an experimental test campaign has been performed in order to validate the CFD analyses and completely characterize the facility operation in free stream condition. Then, it followed a series of experiments with models of increasing size and different shapes in order to determine the blockage effect on the operation of the hypersonic wind tunnel. The following operation of the facility was aimed to study the boundary layer interaction with the ablative process on low temperature ablative models. First these models have been built after having appropriately designed the sintering system. Secondly, we have applied the Planar Laser Induced Fluorescence method to visualize the flow behavior on these naphthalene models: a laminar-turbulent transition due to the ablation process has been observed together with the main flow structures.File | Dimensione | Formato | |
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2018_07_Agostinelli.pdf
Open Access dal 04/07/2019
Descrizione: Testo della tesi
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https://hdl.handle.net/10589/141454