Aerodynamic and Structural Evaluation of an SMA Slat-Cove Filler Using Computational and Experimental Tools at Model Scale

Abstract

Transport class aircraft produce a significant amount of airframe noise during approach and landing due to exposed geometric discontinuities that are hidden during cruise. The leading-edge slat is a primary contributor to this noise. In previous work, use of a slat-cove filler (SCF) has proven to reduce airframe noise by filling the cove aft of the slat, eliminating the circulation region within the cove. The goal of this work is to extend and improve upon past experimental and computational efforts on the evaluation of a scaled high-lift wing with a superelastic shape memory alloy (SMA) SCF. Recent turbulence measurements of the Texas A&M University 3ft-by-4ft wind tunnel allow for more accurate representation of the flow through the test section in computational fluid dynamics (CFD) analysis. The finite volume models used in CFD analysis are coupled to structural finite element models using a framework compatible with an SMA constitutive model and significant deformation, enabling fluid-structure interaction (FSI) analysis of the SCF. Both fully-deployed and retraction/deployment cases are considered. The displacement of the SCF on the experimental model is measured at various stages of retraction/deployment using a laser displacement sensor and digital image correlation system. Due to a lack of structural stiffness in the 3D-printed plastic slat during retraction and SCF stowage, a rigid steel slat is incorporated into the physical model and preliminary wind tunnel tests are conducted at multiple angles of attack.

Design of Shape-Adaptive Deployable Slat-Cove Filler for Airframe Noise Reduction

“…All models are based on a full-scale, freestream-aligned, high-lift airfoil section extracted from the midspan of the Boeing/ NASA Common Research Model (CRM) [41,42]. The models are developed in a similar manner as wind tunnel-scale structure and fluid models from previous work [6,33,[36][37][38]. The geometry employed herein includes an additional SCF profile.…”

“…Following the benchtop models, structural finite element models of the SMA-based SCF design were developed, and optimization was performed with a focus of reducing actuation force required to stow the SCF [33]. Work then shifted toward the development of both computational fluid dynamics (CFD) and fluid/structure interaction (FSI) models to assess the SCF behavior in relevant flowfield environments [36][37][38]. Concurrently with the computational CFD/FSI model development, a scaled physical model with deployable slat/ flaps and a SMA SCF was built.…”

“…Concurrently with the computational CFD/FSI model development, a scaled physical model with deployable slat/ flaps and a SMA SCF was built. Wind tunnel testing at various wing configurations/flow conditions and structural experiments with digital image correlation were performed to begin validation of the computational models [37][38][39]. Further work has also focused on computational modeling of fully mechanized benchtop models [40].…”

“…Here, we propose and test a design methodology that uses finite element structural analysis and CFD simulations. While previous work has focused predominantly on using SMA materials for the SCF [6,33,[36][37][38], a novelty of the present Paper is the consideration of lightweight composite materials for the first time. In particular, the influence of material selection is investigated by comparing three SCF configurational classes:…”

“…1) a uniformly thick (monolithic) SMA SCF, 2) a variable-thickness SMA SCF, and 3) a fiberglass composite SCF having a carefully designed layup. SMA materials are a natural choice for deployable SCFs due to the intrinsic superelastic properties [38]. However, a similar reversible, elastic behavior that permits extreme deformations can also be achieved geometrically, rather than constitutively, by exploiting elastic instabilities, in other words, snap-through buckling [10,14].…”