Joined-Wing Wind-Tunnel Test for Longitudinal Control via Aftwing Twist

摘要

Wind-tunnel tests were conducted to assess the use of aftwing twist for longitudinal control in a joined-wingnaircraft. Forces and moments required for pitch control were measured experimentally, along with limitednchordwise pressure measurements. Comparisons of aerodynamic panel model predictions with experimental datanwere used to calculate camber and center-of-pressure corrections. The lift-curve slopemeasured at four flow speedsncompared favorably to linear predictions over the range of 20u0001nangles of attack. The pitchingmoment coefficientwasnlinear at the three lower flow speeds for untwisted and twist-down aft wings over a narrower range of about 10u0001nangles of attack. The pressure exhibited shifts in the chordwise distribution at angles of attack coinciding with thenchange in themoment curve slope. The large spread in the twist-up aftwing configuration drag and pitching-momentncoefficients indicated flow separation on the aft wing, even at small angles of attack, deterring the twist effectiveness.nIndependent forward and aftwing measurements and more extensive use of pressure sensors are recommended innfuture experiments to confirmthe apparent separation and interference effects thatmust be avoided if aftwing twist isnto be used for pitch control on a joined wing.