Abstract

An aerostructural analysis program was developed to predict the aerodynamic performance of a non-rigid, low-sweep wing. The wing planform was geometrically defined to have a rectangular section, and a trapezoidal section. The cross-section was further set to an airfoil shape which was consistent across the entire wingspan. Furthermore, to enable the inclusion of this multidisciplinary analysis module into an optimization scheme, the wing geometry was defined by a series of parameters: root chord, taper ratio, leading-edge sweep, semi-span length, and the kink location. Aerodynamic analysis was implemented through the quasi-three-dimensional approach, including a three-dimensional inviscid solution and a sectional two-dimensional viscous solution. The inviscid analysis was provided through the implementation of the vortex ring lifting surface method, which modelled the wing about its mean camber surface. The viscous aerodynamic solution was implemented through a sectional slicing of the wing. For each section, the effective angle of attack was determined and provided as an input to a two-dimensional airfoil solver. This airfoil solution was comprised of two subcomponents: a linear-strength vortex method inviscid solution, and a direct-method viscous boundary layer computation. The converged airfoil solution was developed by adjusting the effective airfoil geometry to account for the boundary layer displacement thickness, which in itself required the inviscid tangential speeds to compute. The structural solution was implemented through classical beam theory, with a torsion and bending calculator included. The torque and bending moment distribution along the wing were computed from the lift distribution, neglecting the effects of drag, and used to compute the twist and deflection of the wing. Interdisciplinary coupling was achieved through an iterative scheme. With the developed implementation, the inviscid lift loads were used to compute the deformation of the wing. This deformation was used to update the wing mesh, and the inviscid analysis was run again. This iteration was continued until the lift variation between computations was below 0.1%. Once the solution was converged upon by the inviscid and structural solutions, the viscous calculator was run to develop the parasitic drag forces. Once computation had completed, the aerodynamic lift and drag forces were output to mark the completion of execution.

Highlights

  • Optimization of aircraft components can be achieved through either a series of single-disciplinary optimization stages, or through a coupled multidisciplinary approach [1]

  • The Q3D aerodynamic solver was built utilizing a Vortex Lattice Method (VLM) solver, based on the analysis developed by Katz and Plotkin [3], used to compute the inviscid aerodynamic effects

  • The sectional viscous drag was returned. This process was repeated for each spanwise section, and the summation of these drag forces was taken as the total parasitic drag acting on the wing

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Summary

Introduction

Optimization of aircraft components can be achieved through either a series of single-disciplinary optimization stages, or through a coupled multidisciplinary approach [1]. Building off the work of FEMWET by Elham and van Tooren [2], this implementation sought to develop a simplified, thereby faster to compute, aerostructural modelling approach for low-sweep wings This was comprised of a quasi-three-dimensional (Q3D) aerodynamic solver coupled with a classical bending-torsional structure solver. The effective angle of attack was computed from the induced drag, and the acting parasitic drag force was computed iteratively between an inviscid two-dimensional airfoil panel solver and a direct boundary layer approximation In this implementation, a linear-strength vortex panel method was used to predict the tangential speed distribution along the airfoil surface. An iterative scheme was employed to apply the loads from the VLM to the structure, which deformed to adjust the VLM mesh This process was repeated until the solution had converged, after which the viscous effects were computed, and the multidisciplinary analysis was considered to be complete

Flow of Information
Lift-Structural Coupling
Aerodynamic Coupling
Geometric and Simulation Definitions
Planform Geometry
Airfoil Geometry
Wing Box Geometry
Airflow Properties
Inviscid Aerodynamic Analysis
Surface Discretization
Analysis Components
Mathematical Solution
Force Distribution
Viscous Aerodynamic Analysis
Strip Discretization
Effective Angle of Attack Computation
Inviscid Airfoil Analysis
Airfoil Discretization
Analysis Outputs
Viscous Airfoil Analysis
Laminar Boundary Layer
Transition Condition The transition condition, following the approach of
Turbulent Boundary Layer
Inviscid-Viscous Coupling
Parasitic Drag Computation
Structural Analysis
Wing Box Bending Model
Wing Box Torsion Model
Wing Box Scaling Factors
Wing Loading
Torsional Loads
Bending Loads
Wing Deformation
Twist Angle Prediction
Deflection Prediction
Mesh Deformation
Tested Wing Configuration
Aerodynamic Forces
Resulting Deformation
Computer Performance
Conclusions
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