Influence of empennage on flow over upswept after-body

To provide a foundation of upswept after fuselage drag reduction, the flow patterns and aerodynamic characteristics over two upswept rear fuselages with and without empennages were investigated in a 1.5 by 1.5 meters low speed wind tunnel by the methods of oil flow, smoke wire/laser and force measurement. The results were obtained at 40 m/s and Reynolds number of 1.191 × 10⁵ at angles of attack ranging from -10° to 20°. With the attack angle increasing from negative to positive, the flow over rear fuselage, which is developed from the end of body to forward, goes through three kinds of open separation mode, namely up-separation, non-separation and down-separation. The drag difference between the after-bodies with and without empennages is due to the friction drag on empennages for non-separation mode and is due to separation on the empennages at higher attack angle. The drag reduction caused by separation weakening on vertical tail results in drag increasing slowly with the increase of the positive attack angle.