Experimental study of boundary layer separation in truncated ideal contour nozzles |
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Authors: | Ralf Stark Bernd Wagner |
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Institution: | (1) Institute of Space Propulsion, Lampoldshausen, German Aerospace Center, DLR, 74239 Hardthausen, Germany |
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Abstract: | DLR Lampoldshausen carried out a cold flow test series to study the boundary layer separation and the related flow field in
a truncated ideal contour nozzle. A special focus was set on low nozzle pressure ratios to identify the origin of a locally
re-attached flow condition that was detected in previous test campaigns. A convex shaped Mach disc was found for nozzle pressure
ratios less than 10 and a slight concave one for nozzle pressure ratios more than 20. Due to boundary layer transition at
low nozzle pressure ratios the convex Mach disc is temporary tilted and redirects the flow towards the nozzle wall. A simple
separation criterion for turbulent nozzle flows is presented that fits well for both cold and hot flows. It is shown that
the oblique separation shock recompresses the flow to 90% of the ambience. The separation zone of the presented film cooled
nozzle is compared with a conventional one around 40% longer. Furthermore a relation between shear layer shape and forced
side loads is described.
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Keywords: | Flow separation Ideal contour nozzles Side loads Mach disc Separation criteria |
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