Method for Designing Three-Dimensional Swept Hybrid Wings for Icing Wind-Tunnel Tests

Abstract

Hybrid-wing models are those that present the same leading-edge geometry of the full-scale aircraft wing and a redesigned aft section of reduced chord, such that models can be tested inside an icing wind tunnel. When properly designed, these models reproduce the full-scale flowfield and ice accretions on the leading edge, with reduced tunnel blockage. Although a method exists for designing hybrid airfoils, no systematic method is available in the literature for designing hybrid swept wings. This paper presents a method for designing three-dimensional swept hybrid wings using hybrid airfoils for the purpose of generating full-scale ice accretions, such as those on large commercial aircraft, in icing wind tunnels. An application example using the method is shown for the design of three hybrid wings representing different wing stations of a modern commercial aircraft. Investigations of the effects of tunnel walls, model sweep angle, model aspect ratio, model thickness, and wind-tunnel blockage are also presented. Attachment-line location was used as a first-order parameter for matching full-scale ice shapes, following the findings of previous investigations on hybrid airfoils. Methods for controlling the spanwise variation of attachment line due to flow three-dimensionality were assessed with the use of angle of attack, gap between the model and tunnel wall, aerodynamic twist, and segmented flaps. Finally, model design tradeoffs are presented from the perspective of the hybrid-wing designer between competing performance parameters, such as level of agreement in matching full-scale attachment-line location, wind-tunnel load/speed limits, and model manufacturing/operational complexity.