Author : Robert K. Decker
Publisher :
ISBN 13 : 9781423510048
Total Pages : 102 pages
Book Rating : 4.5/5 (1 download)
Book Synopsis Viscous Drag Measurement and Its Application to Base Drag Reduction by : Robert K. Decker
Download or read book Viscous Drag Measurement and Its Application to Base Drag Reduction written by Robert K. Decker and published by . This book was released on 2002-05 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study two important topics have been investigated. First, a new automation procedure has been developed to detect fringe patterns in oil- film interferograms. The procedure combines a windowed Fourier transform and a cross correlation technique to determine regions where fringes are likely to reside. The cross correlation of a single cycle cosine function and the original intensity produce a filtered result that isolates the information being sought. The automation procedure is able to capture approximately 75% of the fringes in an image but additional refining of the technique could increase this percentage. Second, the effect of viscous fore-body drag on base drag has been investigated on a 2-D ramp model. Measurements made during the study include oil-film interferometry and hot-wire anemometry for viscous fore-body drag, and pressure measurements on the fore-body and base for fore-body and base drag. The results of this investigation show that an increase in viscous fore-body drag has very little effect on base drag, which contrasts previous studies where increases in viscous fore-body drag tended to decrease base drag. This means that a simple jet pumping mechanism is not the sole effect responsible for base drag reduction in this type of geometry. Hot-wire measurements in the wake of the model show that the flow in the base region is devoid of a dominant shedding frequency. It may be possible that the boundary layer somehow affects the vortex shedding mechanism but further investigations would be necessary to demonstrate that this is true.