A submerged inlet has good stealth characteristics and a low external drag, but it also has the disadvantage of low internal flow efficiency. In view of this, a new efficiency enhancement method based on the prepositive synergistic bulge of the inlet’s anterior lip is proposed. Taking the submerged inlet of an aircraft as the baseline configuration, a miniature bulge with a square bottom and an outer convex form is designed in front of the inlet’s anterior lip. Through the convex shape of the bulge, part of the low-energy boundary layer airflow is diverted away from the inlet’s entrance, so that the airflow greatly reduces the flow separation after entering the inlet, and the internal flow performance of the entire submerged inlet is improved. Taking the flow field of an aircraft in the classic cruise state as an example, the simulation analysis results show that the flow field characteristics of the entire submerged inlet are obviously improved after adding the synergistic bulge. The total pressure recovery coefficient of the new inlet configuration increased by 1.36%, the total pressure distortion index decreased by 10.86%, and the body drag only increased by 0.37% compared with the baseline case. According to calculations of synergistic bulge inlet configurations with different design parameters, the effect of this configuration is relatively stable, whereby the aspect ratio of the bulge has the greatest impact on the performance, and its value should not be less than 0.75. In addition to the advantages of not requiring additional components or occupying space and being easy to manufacture, the method of adding a synergistic bulge can improve the aerodynamic performance of the baseline inlet under most cruise flight conditions, and its additional drag is small, which gives it a wide applicability range.

Based on the bionic design of the humpback whale fin, a passive flow control method is proposed to obtain greater flapping lift by applying the wavy leading edge structure to the straight symmetrical flapping wing. The leading edge of the conventional flapping wing is replaced by the wavy shape represented by regular trigonometric function to form a special passive flow control configuration imitating the leading edge of the humpback whale fin. The dynamic aerodynamic performance and flow field characteristics of straight wing and wavy leading edge flapping wing with different parameters are compared and analyzed by CFD numerical simulation. The simulation results show that the wavy leading edge structure changes the flow field of the baseline flapping wing and reduces the pressure on the upper surface of the flapping wing during the process of downward flapping, thereby increasing the pressure difference between the upper and lower surfaces of the flapping wing and increasing the lift. The sensitivity analysis of the design parameters shows that in order to obtain the maximum lift coefficient while losing the least thrust, the smaller amplitude should be selected on the premise of selecting the smaller wavelength. Among the configurations of different design parameters calculated in this paper, the optimal wavy leading edge flapping wing configuration increases the time average lift coefficient by 32.86% and decreases the time average thrust coefficient by 14.28%. Compared with the straight wing, it has better low-speed flight and can withstand greater take-off weight.

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