Abstract
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. 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). 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. 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. 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.
Highlights
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
Compared to the DES/DDES model, improved delayed detached eddy simulation (IDDES) provides shielding against Grid Induced Separation (GIS) and allows the model to run in the wallmodeled LES (WMLES) mode, providing a possibility to simulate an unsteady mode of near-wall boundary layers
RANS is used over the entire angle of attack ranging up to 18° while URANS and IDDES are only applied for the pre- and poststall conditions including 10°, 12°, 14°, 16°, and 18°
Summary
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. 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 [4]. Their effects are highly dependent on aircraft configuration and must be further validated by a flight test program [5]. Wind tunnel and full-scale flight tests were performed on a general aviation configuration by Johnson et al [6] and Meyer et al [7], respectively, to analyze the influence of leading-edge modification on the flow separation state and stall pattern of the wing. Anderson [9] reviewed the primary factors which had affected stall/spin behavior of general aviation aircraft over the history of flight and proposed several prospects for aerodynamic improvements in stall/spin
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