A flow field survey was performed with a 5-hole pressure probe at 1 chord length behind a propeller-wing configuration revealing important qualitative and quantitative information on the propeller dominated interactive flow field. The model, that consists of a low aspect ratio semi-span wing model combined with a 4 bladed tractor propeller, was tested at several low subsonic flow conditions in the Delft University Low Speed Windtunnel. The distribution of total pressure and axial vorticity show, besides the well-known spiral tip vortex, a strong deformation of the slipstream structure. The deformation of the vortex wake is strongly related to the spanwise lift distribution of the propeller/wing configuration which might be used as a starting point for prediction of vortex formation and decay. It also determines the magnitude of the overall induced drag and the deformation process therefore has implications for the proper modelling of slipstreams used within theoretical prediction codes for the analysis of airplane performance. To obtain quantitative information from the field data the theory of Betz and Maskell was applied to determine the lift, the profile drag and the induced drag for both the model with and without running propeller. Comparison of these results with external balance measurements shows a good agreement. The lift distributions which were compared with surface pressure measurements reveal that a considerable amount of swirl is left in the slipstream after passage of the wing; an important observation for future optimisation of propeller-wing configurations. In general the flow field survey with traversing 5 hole probe appears to be a powerful technique to better understand propeller/wing interactive flows.
Experimental analysis of the vortex wake structure behind a propeller-wing configuration
Experimentelle Analyse der Struktur des Wirbelnachlaufes hinter einer Propeller-Tragflügel-Konfiguration
1996
17 Seiten, 20 Bilder, 2 Tabellen, 14 Quellen
Conference paper
English
Experimental Analysis of the Vortex Wake Structure behind a Propeller-Wing Configuration
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