The geometric configurations of serpentine nozzles differ significantly from conventional axisymmetric nozzles, characterized by substantial variations in the wall curvature and an S-shaped centerline. This configuration results in uneven distribution of internal aerodynamic load. Serpentine nozzles are generally thin-walled structures to reduce aircraft’s weight. Consequently, the fluid-structural interaction (FSI) becomes a prominent phenomenon in serpentine nozzles, playing an important role in aircraft design. To examine the FSI phenomenon in serpentine nozzles and its impact on thrust performance, this paper introduces double serpentine nozzles with varying offset ratios. A two-way FSI framework is then established and validated. Subsequent analysis focuses on the deformation characteristics of the nozzle and their effects on the aerodynamic loads on the nozzle wall. Furthermore, the influence of FSI on thrust performance is explored. The results reveal that the FSI phenomenon is evident under different offset ratios. There are two types of nozzle deformation: inward-outward and top-down, with the deformation decreasing gradually with the increase of offset ratio. Notably, the maximum deformation consistently occurs at the middle of the lower wall of the nozzle outlet. Regarding the aerodynamic performance, the nozzle's cross-sectional area expands, transitioning from an initial convergence configuration to a convergence-expansion one. Both the throat area and offset ratio decrease approximately linearly with the increase of the offset ratio. The FSI causes the local high-speed flow region at the junction of the second inflection and the outlet to expand and move downstream, leading to a reduction or even elimination of the downstream pressure peak. In terms of thrust performance, the thrust coefficient increases (when ψ = 0.34, the increase is approximately 0.6%), and the thrust vector angle decreases (when ψ = 0.52, the reduction in thrust vector angle is approximately 23.6%). But the variation trend of both with the offset ratio is consistent with that under uncoupled conditions, and both decrease gradually with increasing offset ratio.

The variable camber technology can adaptively improve the aerodynamic performance of the aircraft, so combining it with the blended wing body (BWB) configuration can further exert its aerodynamic advantages. However, the tailless BWB only uses the trailing edge flap surface for trimming, with a shorter longitudinal moment arm, resulting in a large penalty in trim drag. Therefore, the trimming of drag loss should be fully considered in the design of the variable camber at the trailing edge of BWB. Since the plane parameters would affect the trimming capability of each flap surface at the trailing edge of tailless BWB, this paper adopted the global optimization method to study the drag reduction principle and effects of the variable camber technology at the trailing edge of BWB with different sweepback angles and different wing positions. The results show that, under different lift coefficients, the trim drag loss significantly reduces the drag reduction benefits of the camber variation technology. Secondly, the planar parameters of BWB affect the shock wave intensity and trim ability, thus influencing the drag reduction benefits of the camber variation technology and the deflection angles of the control surfaces. Compared with the baseline configuration, increasing the sweep angle can increase the drag reduction benefits at small lift coefficients and decrease them at large lift coefficients. When the wing position is forward, the drag reduction benefits increase when moment trimming is not considered, but decrease when moment trimming is considered.When designing the variable camber at the trailing edge of the tailless aircraft in engineering, it is necessary to comprehensively consider the drag reduction benefits of the variable camber at the trailing edge and the deflection angle of the flap surface required for deformation.