However, their effects are highly dependent on aircraft configuration and must be further validated by a flight test program.
In addition to the installation of a slat, aerodynamic accessories such as stall strips, wing fences, and vortex generators can be utilized for improving the local stall behavior without major configuration modifications in the final stages of design. One commonly used approach of delaying wing stall is by installing a well-designed leading-edge slat to effectively lower adverse pressure gradients and suppress separation on the upper side as the angle of attack increases. Stall behavior of aircraft is one of the most important aspects that should be emphasized in the preliminary design stage as it directly affects the safety and maneuverability of aircraft during takeoff and landing. By using the evaluation method, together with design rules summarized from the present study, high-lift configuration with mild-stall characteristic can be obtained in the preliminary stage of design. And through further research, an efficient evaluation method that is capable of qualitatively predicting the stall performance of two-element high-lift configuration by stall angle distribution of wing sections is proposed. Based on the analysis of the calculated results, conclusion can be made that the stall behavior of the configurations is directly related to the onset and evaluation of flow separation on the suction side. Focusing on the low-speed stall and poststall conditions, we investigated the aerodynamic characteristics and flow mechanism of high-lift configuration without slats using an improved delayed detached eddy simulation (IDDES) model which is validated by numerical simulations of the Common Research Model (CRM). In order to simplify the manufacturing process or because of the limitation of the propulsion system, business jet, small civil airplane, and turboprop aircraft are always designed without leading-edge slats, which poses a great challenge to the flight safety during takeoff and landing.
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