Influence of Bevel Section on Flow Characteristics of Double Serpentine Nozzle with Bevel

In order to improve fighters' stealth ability and reach an integrated design of the outer fuselage and nozzle, a double serpentine nozzle can be scarfed at the tail according to the aircraft's skin. But the jet flow of the exhaust system is deflected when a nozzle is beveled, which makes the thrust line not completely coincide with the aircraft axis. Different degrees of thrust line cause corresponding deflection torque, which affects the aerodynamics layout of the aircraft and causes difficulties in aircraft control. In this paper, a double serpentine nozzle with bevel which consists of a first bend section, second bend section, and bevel section is taken as the baseline to study the influence of geometric parameters of the double serpentine nozzle with bevel on flow characteristics. Two parameters of the bevel section, angle, and length, were selected to research. Seven nozzles with different deflection angles of the bevel section were numerically simulated. Results show that the aerodynamic parameters of those nozzles are slightly different. The thrust line deflects in the same direction as the changed deflection direction of the bevel section, but the deflection amplitude of the thrust line is significantly smaller than the deflection amplitude of the bevel section. And when deflecting one direction (Y/Z) actively, the other direction (Z/Y) will have the opposite effect. The change of the bevel section deflection angle has a greater impact on the thrust line. Six nozzles with different lengths of the bevel section were selected. Numerical results show that as the length increases, the friction resistance of nozzles increases, and the loss increases. With the increase in the length of the bevel section, the angle between the thrust line and the vertical plane XY is gradually decreasing, so the thrust line deflects close to the bevel section axis. For the angle with the horizontal plane XZ, the thrust line deflects upward when the bevel section lengthens by 7%; then when the length of the bevel section continues to increase, the thrust line deflects downward. The average angle variation in each direction is about 0.1 degrees when the length increases by 7%. In this paper, four flight conditions including subsonic and, supersonic jet conditions are studied. Flight conditions heavily influence the thrust line of the double serpentine nozzle with bevel.