The Preliminary Design of an Aircraft Wing Structure to Meet Aggressive Torque Box Strain Energy and Mass Targets
Stephen WanjihiaA dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Engineering
March 2014School of Engineering and DesignBrunel UniversityLondon, United Kingdom
ATTENTION!IF YOU SEE _ KNOW THAT THERE IS A HIDDEN REFFERENCE THERE. PLEASE CHANGE TO SHOW MARKUP TO SEE IT.Topology Optimization of a Wing Box Rib
This dissertation provides a methodology for generating the preliminary design of an aircraft wing box rib to meet aggressive strain energy and mass targets.Initially research is conducted to investigate the potential benefits and real world applications of topology optimisation; this has the double objective of giving the study a focus while providing initial aircraft wing geometry that a CAD model is built from. Furthermore research is also conducted to investigate the flight missions that the aircraft / type is typically exposed to and in doing so a greater understanding of the maximum wing loading and more importantly the conditions that the aircraft is in during which is achieved.Putting the two together, an aerodynamic study is conducted on the wing CAD model with the boundary conditions that the aircraft experiences when producing maximum wing loading. Therefore the objective of the aerodynamic study is to extract the surface pressures that act on the wing during the critical flight case.With great care the loads along with the CAD model are then transferred from the aerodynamic environment to the structural environment for structural analysis and optimisation. The structural analysis is conducted beforehand using the aerodynamic loads to gain an initial understanding of the stress distribution and displacement within structure. The structural analysis not only provides a better understanding of the structure to be optimised but also acts as a validation tool for the optimised structure. The factor of safety that the pre-optimised structure achieves can be compared to that of the post optimised structure, thus structurally validating the final optimised design.
to my family for their constant love and support and my loving girlfriend for her patience over the years
ACKNOWLEDGEMENTSI would like to thank my supervisor Dr. Narcis M. Ursache for his guidance on the project and also Dr. Jan Wissink for his insightful advice and guidance.
TABLE OF CONTENTS1.Introduction91.1.Context91.2.Background101.2.1.Size Optimisation101.2.2.Shape Optimisation101.2.3.Structural Optimisation111.2.4.Topography111.2.5.Topometry111.2.6.Topology111.3.Purpose111.4.Dissertation Outline112.Literature Review122.1.Approach132.2.Algorithms142.3.Objectives142.4.Domain152.5.Conclusion163.Methodology173.1.Introduction174.Geometry Design184.1.Aircraft Specification184.2.Wing Structure184.2.1.Wing Design194.2.2.Specification204.3.Mission214.3.1.Flight Case225.Aerodynamic Analysis235.1.Introduction235.2.Problem Study255.3.Flow Classification265.3.1.Subsonic vs. Supersonic & Incompressible vs. Compressible265.3.2.Laminar vs. Turbulent275.4.Boundary Conditions275.4.1.Geometry275.4.2.Grid285.4.3.Flow Solver Boundary Conditions285.5.Results295.6.Discussion316.Baseline Analysis336.1.Model Setup and Considerations336.1.1.Approach336.1.2.Geometry336.1.3.Material Property346.1.4.Mesh Creation346.1.5.Loads and Boundary Conditions356.1.6.Hypothesis366.1.7.Results366.1.8.Discussion387.Topology Optimisation397.1.FE Model Setup and Considerations397.2.Approach397.3.Geometry397.4.Material Property and Element property407.5.Loads and Boundary Conditions407.6.Meshing407.7.Analysis Setup407.8.Results417.9.Discussion417.9.1.Project Overview427.9.2.Results Overview437.9.3.Future Work447.9.4.Recommendations448.Conclusion46No table of contents entries found.
LIST OF TABLESTable 1 Wing geometrical specification23Table 2 Cessna Citation Mustang wing spar material properties24Table 3 Cessna Citation Mustang wing spar material properties24Table 4 Take-off flight case conditions25Table 6 Chord-Wise Coefficient of Pressure Distribution (Airfoils 1, 2 & 3), 10 degrees angle of attack32Table 7 Chord-wise Static Pressure Distribution (Airfoils 1, 2 & 3), 10 degrees angle of attack33
LIST OF FIGURESFigure 1Types of structural optimisation, size (top), shape (middle) and topology optimisation (bottom), Courtesy of ((Martin P Bendsoe & Sigmund, 2003))13Figure 2 Topology Optimisation, types of approach, macrostructure (top) and microstructure (bottom), Courtesy of ((G I N Rozvany et al., 1995))16Figure 5 NACA 23014 geometrical points23Figure 6 Critical conditions for a wing box structure (Courtesy of (Michael Chun-yung Niu, n.d.))25Figure 7 C-Mesh geometry around NACA 2301428Figure 9 Flow regime classifications (Courtesy of Dr Mark Jabbal)30Figure 11 Contours of Static Pressure for 10 degrees angle of attack k-omega model (airfoil 1)33Figure 13 Isometric View of Airfoils1, 2 & 3 and front, mid and rear spars geometry in Patran 201237Figure 14 Loads applied to Finite Element Model Patran39Figure 15 Applied load displacement plot (patran)40Figure 16 Finite Element Model Von-Mises Stress40Figure 17 Baseline Design of CCM Wing Ribs44
Contents Abstract Give the reader a brief outline of the dissertation Contents, Table of figures and List of Tables List of Symbols/Nomenclature Introduction Brief introduction to the report, i.e. analysis and studies conducted. Finally, in brief, discussing the aims of the report.Comment by me10stw: MAE 154B Context Justifying topology optimisation Background Brief yet detailed chronological account of optimisation, leading to structural optimisation and finally topology optimisation. Types of optimisation A brief discussion of the different types of optimisation, concentrating on the key differences.Comment by me10stw: See m5 General optimisation Theory, Algorithms and ApplicationsComment by me10stw: See m5Also An intro to Structural Opt Topology optimisation algorithms Multidisciplinary Topology Optimisation Project Description A description of the project (as stated in the project brief) and a breakdown of the major challenges of the project.Comment by me10stw: MAE 154B Delimitations of dissertation A description of the set project boundaries to ensure focus is kept within the study topic i.e. topology optimisation. Methodology Introduction Wing Structure Description of wing structural components Aircraft Selection Justification of aircraft selection through comparative study Airfoil Design Guiding the reader through the design process of the airfoil Geometry Introduction Highlighting the importance of the work conducted herein before providing a brief description of the simulation conducted Description of Software - Aerodynamic Analysis Introduction Highlighting the importance of the work conducted herein before providing a brief description of the simulation conducted Description of Tools - Ansys Workbench Fluid Flow (Fluent) Inputs and Constraints Pre-Analysis boundary conditions Procedure Geometry, Mesh, Physics Setup Results and Discussion Numerical Results, Verification & Validation Conclusion and Recommendations Finite Element Analysis Linear Static Analysis Geometry Properties Boundary Conditions & Loads Meshing Analysis Results Topology Optimisation Model Preparation Meshing Set-up Results Discussion Conclusion
1. To the women of my life:2. 3. Abstract4. 5. Contents, Table of figures and List of Tables6. List of Symbols/Nomenclature7. 8. 9. IntroductionComment by me10stw: MAE 154BWithin this chapter a context for the study is provided, thereafter a brief background of optimisation in general is given before the various types of structural optimisation are identified and covered. Thereafter the purpose of the study is defined before an outline of the report is specified.9.1. ContextFuel costs for the past 23 years have suffered from a constant inflation (Department of Energy and Climate Change 2012) and for a flight company today this accounts to a significant proportion of approximately a third of overall operating fees. As a result, flight companies are making a conscious effort to cut costs from elsewhere in the business; By simply removing an olive from the salad container of each first class passenger, American Airlines are said to have saved up to $500,000 per year (Robinson G & Stern 1997).While Airline business search for margins through budgeting, OEMs are pursuing their margins through efficient designs and less material waste.In an interview Dr. Matthew Gilbert of Sheffield University stated, Over a thirty year lifetime of an aircraft, carrying one kilogram is equivalent to $100,000 of aviation fuel. The importance of reducing aircraft weight can be witnessed in thethrough cases such as of Airbus collaboration with Altair Engineering where the company is reported to have made weight savings of up to 1000kg per A380 (Krog et al. 2004). According to Dr. Matthew Gilberts estimates, that equates to commercial savings of approximately $3.3million each year. Furthermore, the aerospace industry is under immense pressure to reduce emissions, both nationally and internationally, from governments and aviation authorities through key policies such as Flightpath 2050(Parliament 2012), ACARE 2020 (Quentin & Co-chairman 2007).These examples of cost saving were chosen to give the reader an better insight into the pressure, effects and results of minimising expenditure within the aerospace industry. Other methods of achieving methods of achieving this are are through incorporating solutions such as flight model optimisation, incorporating drag reduction devices or structural optimisation.
9.2. The ACARE 2020 vision for commercial transport aircraft targets a 50% reduction per passenger kilometre in fuel cons