Aerodynamic drag reduction through a hybrid laminar flow control and variable camber coupled wing

This paper presents computational fluid dynamics (CFD) results of a transonic transport aircraft wing, featuring a hybrid laminar flow control (HLFC) and variable camber (VC) technology coupling. The goal of the paper is a quantitative assessment of synergistic effects for aerodynamic drag reduction, when combining the possibility of actively shaping the surface pressure distribution of the wing through VC with the passive natural laminar flow aspect of HLFC. Modeling approaches for both VC integration, achieved through deflections of an Adaptive Dropped Hinge Flap (ADHF), and boundary layer suction into a CFD workflow are presented. Transition prediction is accomplished with the y - Ree + Cross-flow (CF) transition turbulence model, and linear stability theory (LST) coupled to a two -N-factor transition prediction method. Both methods reflect synergy-driven effects. While the extent of laminar flow predicted by the y - Ree + CF model is limited, both favorable ADHF settings and boundary layer suction lead to an overall drag reduction. This is correspondingly reflected through the analyses via LST. Furthermore, the latter predicts a pronounced downstream shift in transition position with increasing suction strength, where the inherent differentiation of transition mechanisms in the two -N-factor method between Tollmien-Schlichting (TSI) and cross-flow instabilities (CFI) reflects a marked reduction in TSI N-factors with increasing ADHF deflection angles. Even though N-factors associated to CFI partially increase through ADHF deflections, the intended synergistic effects are represented throughout the investigated parameter range, leading to an increase in the extent of laminar flow for adequate ADHF deflection angles.

Automated summary

This paper presents the computational fluid dynamics results of a transonic transport aircraft wing with a hybrid laminar flow control (HLFC) and variable camber (VC) technology coupling. The study aims to quantitatively assess the synergistic effects of aerodynamic drag reduction by combining the active surface pressure distribution control through VC and the passive natural laminar flow feature of HLFC. Modeling approaches for VC integration and boundary layer suction into the CFD workflow are presented. The results show that optimized ADHF settings and boundary layer suction can reduce overall drag and increase the extent of laminar flow for appropriate ADHF deflection angles.