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Re-Worked Honours Project Plan Analysis of flow around an RS: X Racing 66 windsurfing fin. Report for staff in the Department of Applied Physics, Curtin University of Technology Written by: Ketesse Hansen (Student identification: 13937832) Supervisors: Dr Tim Gourlay Dr Andrew King Submitted 17 th October, 2011 Curtin University of Technology Perth, Western Australia Abstract The behaviour of fluid flowing past a RS:X Racing 66 windsurfing fin at different angles of attack was studied both computationally and experimentally. This was achieved by creating a three dimensional computational model of the fin, which was both used to produce a physical model for experimental testing, and as the basis for analysis using the fluid analysis program, OpenFOAM. The experimental analysis of the flow was performed in the Curtin wind tunnel, and the results from these experiments were then compared against the results of the computational fluid analysis. The effects compared were flow separation, cross flow and tip vortices. 2 Contents Abstract ......................................................................................................................... 2 Contents ........................................................................................................................ 3 List of Figures................................................................................................................. 5 List of Tables ................................................................................................................ 10 1. Introduction......................................................................................................... 11 2. Background .......................................................................................................... 12 2.1. Foils ............................................................................................................. 12 2.2.1. NACA foils ............................................................................................ 12 2.2.2. NACA 6 series ...................................................................................... 13 2.2.3. RS: X Racing 66 Sailboard Fin .............................................................. 16 2.2.4 Consequences of similarity to NACA 65-009 ...................................... 18 2.3 Computational Fluid Dynamics (CFD)...................................................... 18 3. Computer generated model ................................................................................ 19 3.1. Measuring the Fin ....................................................................................... 19 3.1.1. Coordinate System .............................................................................. 24 3.2. Comparison to NACA foil sections .............................................................. 25 3.3. Leading Edge Radius .................................................................................... 28 3.4. Trailing Edge ................................................................................................ 34 3.5. AutoCAD ...................................................................................................... 35 3.6. STL Files ....................................................................................................... 38 4. Experimental Analysis ......................................................................................... 39 4.1. Wind Tunnel ................................................................................................ 40 4.1.1 Dynamic Similarity ...................................................................................... 40 4.1.2 Required test speed range ......................................................................... 41 4.1.3 Boundary layer thickness: wind tunnel flow .............................................. 42 4.1.4 Boundary layer thickness ........................................................................... 43 4.1.5 The expected lift force acting on model inside the wind tunnel ............... 44 4.2. Rapid Prototyper ......................................................................................... 50 4.3. Tell Tales ...................................................................................................... 51 4.4. Experimental procedure.............................................................................. 52 4.4.1 Experimental set up ................................................................................... 52 4.4.2 Experimental results................................................................................... 57 4.4.3 Application of experimental results to full-scale model ............................ 65 5. Computational Analysis ....................................................................................... 66 5.1. XFOIL ............................................................................................................ 66 5.1.1 Boundary layer analysis using XFOIL .......................................................... 66 5.1.2 Reynolds and Mach numbers of the wind tunnel flow .............................. 67 5.1.3 Boundary layer and pressure distribution ................................................. 68 5.2. OpenFOAM .................................................................................................. 72 5.3. Computational procedure ........................................................................... 73 5.2.1 Pre-processing ............................................................................................ 73 5.2.2 Processing ................................................................................................... 73 5.2.3 Post-processing .......................................................................................... 74 5.4. Computational results ................................................................................. 74 5.3.1 Comparison to experimental results .......................................................... 74 5.3.2 Computational results for racing speed applications ................................ 80 3 5.3.3 Conclusions based on computational results ............................................ 88 6. Comparison of results to results expected for a NACA 65-009 .......................... 88 7. Conclusion ........................................................................................................... 89 8. Future Work ........................................................................................................ 90 9. Acknowledgements ............................................................................................. 90 10. Nomenclature.................................................................................................. 90 11. References ....................................................................................................... 91 12. Bibliography .................................................................................................... 94 13. Appendix ......................................................................................................... 95 13.1. Matlab Code ............................................................................................ 95 13.1.1 mysolvemissing.m .................................................................................... 95 13.1.2 interpPoints.m .......................................................................................... 95 4 List of Figures Figure 1: Cambered foil…………………………………………………………………………………………..12 Figure 2: Typical method of writing NACA 6-series foil……………………………………………13 Figure 3: NACA 6-series designation for foils with thickness/chord ratios of less than 12%, and the low-drag range omitted…………………………………………………………………….15 Figure 4: RS: X Men’s Sailboard……………………………………………………………………………….16 Figure 5: Men’s RS: X Racing 66 fin (side A)…………………………………………………………….17 Figure 6: The wind acting on the sail causes the board to move at an angle to the heading, and this is the angle of attack of the flow with respect to the fin. (Not to scale)………………………………………………………………………………………………………………………17 Figure 7: 5mm intervals along y-displacements alpha, bravo and charlie, fin side A…………………………………………………………………………………………………………………….……….20 Figure 8: XZ cross section (y-displacement alpha), shown here on axes of unequal scale………………………………………………………………………………………………………………………..21 Figure 9: XZ cross sections of y-displacements alpha and bravo………………………………22 Figure 10: Leading edge of the fin shown using the excel model of the fin viewed in the XY plane, shown here on axes of unequal scale…………………….………………………….24 Figure 11: Profile of the fin for each cross section in terms of the percentage of total chord length, shown here on axes of unequal scale………………………………………………..26 Figure 12: Profile of the RS: X Racing 66 windsurfing fin compared against several NACA sections…………………………………………………………………………………………………………27 Figure 13: NACA 65-009 foil section profile compared with the profile of the RS: X 66 windsurfing fin (y-displacement: charlie)………………………………………..………………………28 Figure 14: Leading edge showing measured points a, b and c, which were used to determine the leading edge radius. Also shown are the associated (calculated) points describing the surface of the leading edge radius. The above diagram was produced from the data measured for y-displacement delta………………………………….29 Figure 15: Calculation of the leading edge radius……………………………………………………30 Figure 16: Trigonometry used to describe
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