XFLR5 Analysis of foils and wings operating at low Reynolds numbers Guidelines for QFLR5 v0.03 1/58 October 2009 TABLE OF CONTENTS 1 PURPOSE ...................................................................................................................................................................................................... 4 2 INTRODUCTION .............................................................................................................................................................................................. 4 2.1 Code limitations and domain of validity .......................................................................................................................................... 4 2.2 XFLR5's development history.......................................................................................................................................................... 4 2.3 Code structure .................................................................................................................................................................................. 5 3 FOIL ANALYSIS AND DESIGN MODES ............................................................................................................................................................ 6 3.1 General.............................................................................................................................................................................................. 6 3.2 Direct Analysis [Oper]....................................................................................................................................................................... 6 3.2.1 Foil object 6 3.2.2 Foil Modification 6 3.2.3 Analysis/Polar object 7 3.2.4 Operating Point (OpPoint) object 7 3.2.5 XFoil analysis 8 3.2.6 XFoil errors 9 3.2.7 Session example – Direct Analysis 9 3.3 Full Inverse Design [MDES] and Mixed Inverse Design [QDES].................................................................................................. 9 3.3.1 General 9 3.3.2 Session example – Full Inverse Design 10 3.3.3 Session example – Mixed Inverse Design 10 4 FOIL DESIGN ............................................................................................................................................................................................... 10 4.1 General............................................................................................................................................................................................ 10 4.2 B-splines main features.................................................................................................................................................................. 11 4.3 Spline Points main features ........................................................................................................................................................... 11 4.4 Leading and trailing edge............................................................................................................................................................... 11 4.5 Output precision.............................................................................................................................................................................. 11 5 3D ANALYSIS .............................................................................................................................................................................................. 11 5.1 Theory - General............................................................................................................................................................................. 11 5.2 Wind and body axis, sign conventions.......................................................................................................................................... 12 5.3 Wing Definition................................................................................................................................................................................ 14 5.4 Reference area for aerodynamic coefficients............................................................................................................................... 15 5.5 Flaps 15 5.6 Body Design.................................................................................................................................................................................... 16 5.6.1 Modeling options 16 5.6.2 Import/export of body data 16 5.7 Plane Definition............................................................................................................................................................................... 16 5.7.1 Surface assemblies 17 5.7.2 Tip Patches 17 5.8 Inertia estimations .......................................................................................................................................................................... 17 5.9 Mesh 19 5.9.1 Panel arrangement - VLM analysis 20 5.9.2 Panel arrangement - 3D panel analysis 20 5.9.3 Body – Wing connections 22 5.10 Symmetry ........................................................................................................................................................................................ 22 5.11 Viscous and inviscid calculations .................................................................................................................................................. 22 5.12 Lifting Line Theory (LLT) - Non Linear.......................................................................................................................................... 23 5.12.1 General 23 Guidelines for QFLR5 v0.03 2/58 October 2009 5.12.2 Limitations of the LLT 25 5.12.3 Precautions with the LLT 25 5.12.4 2D vs. 3D 25 5.12.5 Viscous and inviscid calculations 25 5.12.6 Lift center of pressure 26 5.12.7 Downwash 26 5.13 Vortex Lattice Method (VLM) - Linear........................................................................................................................................... 26 5.13.1 VLM General principles 26 5.13.2 Lift force and lift coefficient 27 5.13.3 Limitations of the VLM 27 5.13.4 VLM alternative method 28 5.13.5 Panel disposition for VLM 29 5.14 3D Panel Method - Linear.............................................................................................................................................................. 30 5.14.1 General Principles 30 5.14.2 Boundary Conditions (BC) 31 5.14.3 Validation 31 5.15 Analysis considerations.................................................................................................................................................................. 33 5.15.1 General Limitations 33 5.15.2 Selection of an Analysis Method 33 5.15.3 Core radius 34 5.15.4 Sideslip 35 5.15.5 Trefftz Plane, far field and near field analysis 35 5.15.6 Linear and non-linear behavior 35 5.15.7 Non-Linear Implementation 37 5.15.8 Tilted Geometry – VLM and 3D Panel Analysis 37 5.15.9 Wake roll-up – VLM and 3D Panel Analysis 39 5.16 Moments.......................................................................................................................................................................................... 41 5.17 Neutral point, Center of pressure, Static Margin.......................................................................................................................... 42 5.18 Efficiency factor............................................................................................................................................................................... 43 5.19 Wing Operating Points and Wing Polars ...................................................................................................................................... 44 5.20 Control analysis – Polar Type 5 and Type 6 ................................................................................................................................ 45 5.20.1 Description 45 5.20.2 Method 45 5.21 Interpolation of the XFoil-generated Polar Mesh.......................................................................................................................... 46 5.22 Streamlines ..................................................................................................................................................................................... 47 5.23 Comparison to experimental results.............................................................................................................................................. 48 5.24 Comparison to wind tunnel data.................................................................................................................................................... 48 5.25 Comparison to Miarex and AVL results ........................................................................................................................................ 51 5.26 Session example – Wing Analysis ................................................................................................................................................ 54 5.27 Non convergences.......................................................................................................................................................................... 55 6 CODE SPECIFICS .......................................................................................................................................................................................