Numerical Evaluation on Large Ground-Effect Seaplane at Takeoff with Power Augmented Ram

Abstract

Power-augmented ram has been considered as a promising solution for increasing lift coefficients for large ground-effect seaplanes that typically are required to take off at sea. To date, however, a quantitative evaluation of the power-augmented ram (PAR) technique is still lacking, except for a few conceptual analyses; and its possible technical barriers are unclear. In this study, a typical large-scale ground-effect vehicle is employed to assess the effect of the PAR on lift enhancement at takeoff using numerical simulation. The results show that high-lift enhancement can be obtained as front-installed engine jets ram into the open cavity between a wing and the ground. The jet flow produces high pressure on the lower surface of the wing, significantly increasing the lift. However, the high pressure is primarily imposed on the trailing-edge flap that is deflected down at takeoff, thus yielding a large nosedown pitching moment that is basically proportional to the lift increment. The extra pitching moment will pose a challenge to trimming the seaplane with conventional elevators. Reasonable designs (including multiple engine layouts, increasing nozzle area, and decreasing nozzle velocity) can improve the undesired pitching moment, thus achieving better aerodynamic performances.