Hinge Moment Reduction for the AG(EH) Main Strut-Pod-Foil Assembly by use of Trailing Edge Tabs.
DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA MD SHIP PERFORMANCE DEPT
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Hydrodynamic loading on a 112th scale model of the AGEH main strut-pod-foil was experimentally examined at various velocities, depth of hydrofoil submergence, strut-pod pitch angles, and foil angles of attack. The results, which are in agreement with previous experiments, show that the lift center of pressure at zero angle of attack for this particular foil aspect ratio 3, taper ratio 0.3, and leading edge sweep angle 0.724 rad or 41.5 deg is located at 70 to 90 percent of the mean geometric chord. Thus, the experimental results could not be compared directly to the empirical two-dimensional theory that was developed since it had been assumed that this lift acted at midchord. Various families of fixed tabflaps were added to the trailing edge of the foil to determine the effectiveness of such tabflaps in reducing the foil pitching moment around the foil hinge. It was shown that such tabflaps can significantly reduce this moment but at a drag penalty. For example, for the particular strut-pod-foil system evaluated, to reduce the moment to zero would result in a 12 to 15 percent increase in drag. Author
- Marine Engineering
- Fluid Mechanics