Ventral Nozzle Research Articles

Propulsion-induced aerodynamic effects measured with a full-scale STOVL model

Propulsion-induced aerodynamic interference effects are presented for a full-scale, powered, STOVL fighter aircraft model. The ejector-lift/vectored thrust configuration, designated the E-7A, was tested at low speed in the 40by 80and 80by 120-ft wind tunnels of the National Full-Scale Aerodynamics Complex located at NASA Ames Research Center. Aerodynamic effects on vehicle lift, drag, and pitching moment are presented over a range of effective velocities for simultaneous operation of all lifting jets. The jet/airframe interactions for separate operation of the lifting ejector system and vector able ventral nozzle are also presented. Ejector and engine inlet momentum effects were fully simulated in these full-scale, powered tests. The jet thrust vector angle of the ventral nozzle was varied to simulate transition from hover to wingborne flight modes. When the lifting ejector system and ventral nozzle are operated simultaneously, the induced effects on lift decrease as the thrust vector angle of the ventral nozzle approaches the horizontal. A negative increment in drag is produced over a narrow portion of the transition speed range when the ejectors and ventral nozzle are operated together. Aerodynamic induced effects of the ejector system measured at full-scale compare well with the small-scale data. Changes in lift and pitching moment due to ventral nozzle operation are smaller at full scale.

Flow in a ventral nozzle for short takeoff and vertical landing aircraft

Short takeoff and vertical landing (STOVL) aircraft are planned for possible future development. For these aircraft, the same propulsion system will provide power for lift, hover, and horizontal flight. To accomplish this, many designs include a ventral nozzle to provide part of the vertical thrust required. Understanding and predicting the internal aerodynamic flow caused by a single exhaust duct opening are highly desirable in assessing this concept. This paper presents a numerical simulation of a ventral nozzle and compares the results with experimental data. Comparisons include visualizations of the flow along the ventral duct walls and in the tailpipe plane of symmetry. Performance calculations are also compared with measured values.