Analysis-driven Design Optimization of a Sma-based Slat-cove Filler for Aeroacoustic Noise Reduction

Abstract

Airframe noise is a significant component of environmental noise in the vicinity of airports. The noise associated with the leading-edge slat of typical transport aircraft is a prominent source of airframe noise. Previous work suggests that a slat-cove filler (SCF) may be an effective noise treatment. Hence, development and optimization of a practical slat-cove-filler structure is a priority. The objectives of this work are to optimize the design of a functioning SCF which incorporates superelastic shape memory alloy (SMA) materials as flexures that permit the deformations involved in the configuration change. The goal of the optimization is to minimize the actuation force needed to retract the slat-SCF assembly while satisfying constraints on the maximum SMA stress and on the SCF deflection under static aerodynamic pressure loads, while also satisfying the condition that the SCF self-deploy during slat extension. A finite element analysis model based on a physical bench-top model is created in Abaqus such that automated iterative analysis of the design could be performed. In order to achieve an optimized design, several design variables associated with the current SCF configuration are considered, such as the thicknesses of SMA flexures and the dimensions of various components, SMA and conventional. Designs of experiment (DOE) are performed to investigate structural response to an aerodynamic pressure load and to slat retraction and deployment. DOE results are then used to inform the optimization process, which determines a design minimizing actuator forces while satisfying the required constraints. INTRODUCTION In transport-class aircraft, conventional high-lift systems (e.g., leading-edge slats and trailing-edge flaps) are used to augment lift and improve stall characteristics at the low speeds required for landing. These multi-element airfoil systems nest tightly in the cruise configuration to minimize drag. The deployed multi-element airfoil system, however, presents many geometric discontinuities to the aerodynamic flow, such as edges, gaps and cavities. These geometric discontinuities are the cause for the unsteady aerodynamics that is the source for significant acoustic noise, termed airframe noise. The flow characteristics, noise production mechanisms and notional concepts for mitigation of slat noise in particular have been studied extensively. The concept of the slat-cove filler (SCF) was introduced several years ago as a possible way to fill the cavity behind the deployed slat in order to reduce the unsteadiness in the flow and, thereby, reduce the radiated acoustic noise. Various idealized versions of the SCF concept have been considered by multiple research groups and the concept has been proven, both computationally and experimentally, to be effective at reducing slat noise [1–3]. This work considers to use of shape memory alloys (SMA) materials as flexures in a leading edge SCF that can be used to reduce the aeroacoustic noise produced by the wing of a typical transport aircraft. Specifically, we perform analysis-driven design optimization of the SCF, which is currently in the developmental stage. SMAs are attractive for use in morphing structures because 1 https://ntrs.nasa.gov/search.jsp?R=20140002895 2017-09-14T04:10:46+00:00Z

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Cite this paper

@inproceedings{Scholten2013AnalysisdrivenDO, title={Analysis-driven Design Optimization of a Sma-based Slat-cove Filler for Aeroacoustic Noise Reduction}, author={William Scholten and Darren Hartl}, year={2013} }