VORTEX SEPARATION ON SLENDER BODIES OF ELLIPTIC CROSS SECTION.
MASSACHUSETTS INST OF TECH CAMBRIDGE AEROPHYSICS LAB
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The lift on slender bodies at high angle of attack is strongly influenced by the separation of a pair of vortices from the lee side. An analytical model of the vortex separation was developed which predicts the vortex development and the consequent nonlinear lift distribution on bodies of elliptic cross section and very general longitudinal contour. The report describes comparisons of the theory with subsonic wind tunnel tests on families of body shapes. Nose contours included pointed ogives, blunt ogives, and hemispheres. Body fineness ratios from 4 to 15 were tested and cross sections from circular to 3.51 ellipses. In addition the elliptic bodies were tested with major axes in and normal to the pitch plane. All cases were run with and without boundary layer trips at angle of attack up to 28 degrees. Vortex trajectories, obtained from the behavior of tuft grids, were in general agreement with theory. Normal force and pitching moment predictions also agreed with experiment until the theory failed at high angles of attack. Limitations on the validity of the analysis were thus experimentally established. The predicted locations of separation were generally quite far around to leeward from the positions measured by a China clay technique. Author
- Fluid Mechanics