Design of 3D swept wing hybrid models for icing wind tunnel tests

Aerodynamics;wing design;aircraft icing;wind tunnel;icing;ice shape;Accretion;hybrid;sweep;swept;wing;computational fluid dynamics (CFD);aircraft certification

Camarinha Fujiwara, Gustavo ; Bragg ; Michael B.

关键词: Aerodynamics;    wing design;    aircraft icing;    wind tunnel;    icing;    ice shape;    Accretion;    hybrid;    sweep;    swept;    wing;    computational fluid dynamics (CFD);    aircraft certification;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/72880/Gustavo%20Eidji_Camarinha%20Fujiwara.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The study of aircraft icing is critical to ensure the safety of any aircraft that might experience icing conditions in flight, including general, commercial, and military aviation. The certification of modern commercial transports requires manufacturers to demonstrate that these aircraft can safely operate during icing conditions through a set of flight tests, consistent with the standards set forth by the Federal Aviation Administration.This is often expensive and challenging to find the appropriate icing test conditions. Thus, both computational methods and icing wind tunnel experiments are utilized during the design and certification of aircraft ice-protection systems to provide a controlled and repeatable environment to mitigate risks, reduce costs, and validate the existing computational icing tools.However, the existing icing wind tunnel facilities cannot accommodate large wings such as those found on modern commercial aircraft without being dramatically scaled. Two methods of scaling exist. The first geometrically scales the entire geometry to fit inside the tunnel test section and then scales the icing conditions to obtain icing similitude. The second maintains the full-scale leading edge of the reference geometry and replaces the aft section with a truncated trailing edge that produces a similar flowfield around the leading edge with a significantly shorter chord, reducing model size and tunnel blockage. This type of model is referred to as a hybrid and its biggest advantage lies in the fact that it is designed to produce full-scale ice shapes, while reducing or even eliminating the need for icing scaling. While a design method for a straight, untapered hybrid wing is well documented and there is a broad set of experimental data available, the design of a swept, hybrid wing lacks both a design method and experimental data.This thesis established a design method for large hybrid swept wings that reproduce full-scale ice accretions through icing wind tunnel tests. The design method was broken down in two steps: 1) A 2D hybrid airfoil design, and 2) A 3D hybrid swept wing design. Multiple existing computational tools were employed and several parametric studies performed.It was shown, in 2D, that matching the stagnation point location on the leading edge of the hybrid airfoil had a first-order impact on matching the full-scale ice shape, while matching the suction peak magnitude and location had a second-order effect. The closer to the leading edge lift was generated for a given hybrid design, the less total load was required to reach the same stagnation point location. As an implication, more front-loaded airfoils required less lift than more aft-loaded ones to reach the same stagnation point location on a hybrid airfoil. More front load also increased the risk of flow separation near the leading edge, while more aft load increased the risk of separation near the trailing edge. Finally, higher hybrid scale factors were shown to increase the risk of flow separation.In 3D, sweep angle was shown to be the primary cause for attachment line location spanwise variation, while aspect ratio did not have a significant impact. Matching attachment line location on the leading edge of the hybrid wing model also had a first-order impact on matching ice shape, similar to matching stagnation point location in 2D hybrid airfoils. More front-loaded 3D hybrid wing models not only yielded less total load to reach the same centerline attachment line location, but also showed the additional benefit of reducing the attachment line location spanwise variation. The attempted spanwise load control techniques had different effectiveness on the hybrid wing models. Adding a sidewall gap between the model and the outboard sidewall helped prevent flow separation near the wingtip, but did not effectively change the attachment line slope across span. The use of segmented flaps to equalize load across span was found to be highly dependent on the model aspect ratio and was ineffective for values lower than 2. Additionally, thicker models relatively to the wind tunnel test section yielded more tunnel blockage, presenting a significant effect on suction peak magnitude for values of tunnel height over model chord h/c lower than 2.Finally, 3 hybrid wing models were designed utilizing the established design method to represent three selected stations of the 65%-scaled Common Research Model, to be tested in the 6 by 9 ft. test section of the NASA Glenn Icing Research Tunnel. 3D aerodynamic and ice accretion simulations were performed utilizing Fluent (3D RANS solver) and LEWICE3D (ice accretion code) to show the successful performance of these models in predicting the full-scale ice accretions for a set of different aerodynamic and icing conditions.